Roadtrek 210 4L80E transmission overheating on mountain climbs

[TWX]

So we just did a long trip in our Roadtrek 210 based on a 2005 Chevrolet Express 3500 from Phoenix out the I-10 through Quartzsite, up through Parker on the Colorado River, through Needles, through the east side of the Sierra Nevadas, across the range through Yosemite, south on the west side of the range, and back down to the I-10 to return home. Having already seen that the van likes to get a bit warm, I took the Linear Logic Scangauge III out of my Frontier and put it into the van, figuring out how to monitor both coolant temp and transmission temp.

On our way out, going through the high desert on I-40 climbing out of the Colorado River valley we saw temps start to climb. The transmission led the way, staying consistently a few degrees higher than the coolant:

View media item 447674
At this stage we knew to keep a close eye on things.

During the trip on the eastern side, we tried to go up from Lone Pine to the Mt. Whitney Portal up Portal Road, but the temps got so hot that the van started chiming to look at the gauges. The temps were crossing 250, with again the transmission leading the engine by several degrees. We ended up going back down the mountain and finding a place to park and let it cool off. We did end up running the heater to start that cooling process. Sorry, I don't have a picture, not sure if my wife captured one or not.

Fortunately on this leg, most of the trip was in cooler alpine climate, where if we needed to run the heater with the windows down it was not such a big burden. When we saw the temps climbing we would do this and watch the coolant temp come down first, then the transmission temp would follow.

This was the reading going up into King's Canyon NP from Tulare:

View media item 447675
What we noticed, the transmission temp would climb even on downhill, if we were using transmission gear-down and engine braking to slow our descent. This makes me think that the heat comes from the torque converter in the 4L80E transmission, specifically when the transmission is engaged at the torque converter well above the stall-speed. I don't know what the K-factor for the TC in my van is, but when engaged without the lockup engaged it gets hot. Tow/Haul mode similarly contributes to more heat even if it means more usable power by delaying upshifts, I suspect that the lockup clutch isn't engaging in Tow/Haul mode.

Since this pattern seemed to work we started doing the heater thing more proactively by the end of the trip. We had the engine actively cool with the transmission still getting pretty hot going into Sequoia NP with the heat running from the moment we reached the base of the climb:

View media item 447673
I mention all of this because it leads me to believe that it's not so much the radiator that's the weakness as it is the transmission cooler. The cooling-loop that puts hot transmission fluid through the radiator on older GMT-610 vans with the 4L80E is causing the coolant to be heated up after the transmission fluid is already hot. It's not the motor primarily causing the thermal issues on this platform.

So I'll likely be looking into how to cool the transmission fluid. I may look at using an old AC condenser coil or a huge aftermarket transmission cooler, installing electric fans on it, and adding baffling to keep the airflow from the grille going through the radiator rather than around it. If that doesn't do it then it might be time for a bigger/better radiator, but if I can do it without having to swap radiators then keeping a stock radiator would make for easier on-the-road repairs.

 

[TWX]

For anyone with a Scangauge product, this is the X-gauge that worked for monitoring the transmission temp on the 2005 Chevrolet Express 3500:

Gauge	TXD	RXF	RXD	MTH	Name	Notes
Transmission Temperature	6C18F122194001	046205190640	3008	00090005FFD8	TFT	Degrees Fahrenheit

 

[booster]

I am very surprised you didn't wind up in transmission "overheat" mode which ours did at 240*F, essentially stopping us on a curvy climb in Rocky Mountain National Park. I hope you have DexVI fluid in the trans as those temps are way too high for DexIV.

I think it would be good to get you to the posts from a number of years ago on overheating 4L80 transmission Chevies. I worked on it for years, literally, before getting to a solution that worked. Here is the list that all helped some, but didn't fix the issue.

Add on Spal fans in front of the radiator.

Big add on cooler with the radiator still also cooling.

Two big coolers on the trans with no radiator in the cooling of the trans.

A two core radiator change and tests done similar to above.

Bypass air blocking around the radiator and even the wheelwell frontal points to increase underbody low pressure to improve airflow and bypasses.

Using tow haul.

Not using tow haul.

So what fixed, with some downsides, our issue under almost all conditions?

Reprogram the shift points, up and down, and the torque converter lockup, both on point and release point, for the transmission. This change is probably 90+% of our cooling help, with the big radiator and other stuff helping mainly the engine temp as the trans is not through the radiator, just two coolers.

The torque converter being unlocked during high engine output is going to overheat the transmission, plain and simply whenever and wherever it happens.

My past discussions include screenshots of the programming grids that I used and an explanation of why they were done the way I did them the way I did. Others have taken our programming and tailored it to their personal driving styles, but the goal is the same in that you need to get the converter locked and rpm high enough to generate the horsepower to move the van with it locked (no converter torque multiplier when it is locked). It is way, way to much information to try to explain here, so I will dig out the relevant discussions if I can find them all and link them in this discussion.

 

[booster]

Some links

This trans cooler, grille, airflow stuff link 1

Another discussion link 2

Cooling stuff link 3

4 pages of programming stuff link 4

More programming discussion link 5

There may be more, but these are the ones I could find readily

 

[TWX]

@booster Thanks, I'll go through those links.

We only hit a problem where the van's OE systems alerted us on the Mt. Whitney drive. We definitely crossed the 240° mark on that drive.

I'm always on the fence about using the within-radiator transmission cooling loop or not, on early Nissan Frontier D40s the thing would break and lead to a condition affectionately referred to as "Strawberry Milkshake of Death" when the transmission fluid and coolant mixed. The system within the GMT-600/610 might be more robust but it's still a point of concern.

The main reason why I would keep the in-radiator transmission heat exchanger is that the fluid method seems like it would conduct heat more effectively than using just air to do it.

A guy I know had cooled the transmission in his '72 Dodge Monaco station wagon by building a cooling loop that literally ran around the entire perimeter of the car behind the bodywork, with both finned lines and finned cooler assemblies located where there was room and good airflow. Suffice it to say that was a rather extreme solution.

My van is going to need new headlights, so if I end up replacing them I'll do a bunch of measuring while the front end is apart, see if I can come up with something that might work well. I've been eyeing a Derale "Hyper-Cool" dual fan cooler because it might simplify the install with its integrated fans. There's enough gap between the grill and the AC condenser that it should fit as well, and with the fans it would help cool the transmission even when the vehicle is stopped or moving very slowly. I might even be able to position it where it's not dumping all it's air straight onto the AC condenser and radiator, potentially improving the thermal efficiency of all cooling slightly.

I've been attempting to educate myself on older tube and fin, vs plate and fin, vs stacked plate, but I don't see a lot of hard information, just generalities without supporting testing. My original idea would've been to get a big old AC condenser from a 1970s automobile, something the size of an automotive radiator, and use it, basically filling the whole area that the grille and radiator offer. Supposedly the newer types are more effective in some regards but they require proper airflow to see those benefits. I'm left wondering if a transmission cooler using existing airflow (ie factory cooling fan and vehicle motion) would really see benefit from the plate-type coolers occupying only part of the grille opening.

 

[booster]

@booster Thanks, I'll go through those links.

We only hit a problem where the van's OE systems alerted us on the Mt. Whitney drive. We definitely crossed the 240° mark on that drive.

I'm always on the fence about using the within-radiator transmission cooling loop or not, on early Nissan Frontier D40s the thing would break and lead to a condition affectionately referred to as "Strawberry Milkshake of Death" when the transmission fluid and coolant mixed. The system within the GMT-600/610 might be more robust but it's still a point of concern.

The main reason why I would keep the in-radiator transmission heat exchanger is that the fluid method seems like it would conduct heat more effectively than using just air to do it.

A guy I know had cooled the transmission in his '72 Dodge Monaco station wagon by building a cooling loop that literally ran around the entire perimeter of the car behind the bodywork, with both finned lines and finned cooler assemblies located where there was room and good airflow. Suffice it to say that was a rather extreme solution.

My van is going to need new headlights, so if I end up replacing them I'll do a bunch of measuring while the front end is apart, see if I can come up with something that might work well. I've been eyeing a Derale "Hyper-Cool" dual fan cooler because it might simplify the install with its integrated fans. There's enough gap between the grill and the AC condenser that it should fit as well, and with the fans it would help cool the transmission even when the vehicle is stopped or moving very slowly. I might even be able to position it where it's not dumping all it's air straight onto the AC condenser and radiator, potentially improving the thermal efficiency of all cooling slightly.

I've been attempting to educate myself on older tube and fin, vs plate and fin, vs stacked plate, but I don't see a lot of hard information, just generalities without supporting testing. My original idea would've been to get a big old AC condenser from a 1970s automobile, something the size of an automotive radiator, and use it, basically filling the whole area that the grille and radiator offer. Supposedly the newer types are more effective in some regards but they require proper airflow to see those benefits. I'm left wondering if a transmission cooler using existing airflow (ie factory cooling fan and vehicle motion) would really see benefit from the plate-type coolers occupying only part of the grille opening.

I had read about the Nissan cooler problems, no excuse for that these days. Most cooler leaks I have seen are at the fittings in or the big sheet metal nut holding the cooler into tank, but both leak to the outside and not into the water.

Fluid to fluid coolers are more efficient than fluid to air cooler, unless the coolant fluid is nearly the same temp as the fluid being cooled, then they are much less effective than air.

As I mentioned earlier and on other discussions also. Many users have not believed that coolers would not be effective on the Chevies and have tried to do it with coolers, all but one unsuccessfully. The one that worked used a standalone cooler under the van that was a very large, very thick with a full time high CFM fan on it. He said he towed with that setup all the time and didn't overheat. He had the two core radiator to cool the water while towing. My guess is that the cooler was so big and dumping so much heat, it would both block too much air to the radiator and also heat the air through so it was too hot to cool the radiator well so they put it underbody.

You probably saw pix of our coolers in the links. They are the top quality, highest efficiency Setrab coolers that are two inches thick. They would not cool the trans enough with fans on and radiator in or out of the loop. They are as much as I would put in front of the radiator. They overlap the fans so if the fans are on they do pull some air through to help out, but since the reprogramming we barely ever use the add on fans as the mechanical fans it plenty. Very hot outside and low speed city driving where we can't lock up as much will make me turn on the fans, though, usually early if I know about it to precool the radiator a bit. We have used them on the Rocky Mountain climb to test and they did keep us cooler, but we were OK without too just not as cool. We shoot to stay under 210* on both the trans and the engine and can hold that now unless it is a very, very steep climb that requires low gear to pull the hill because you can't get the trans to lock in low gear. Be aware that stock, the Chevy will shift out of low to second even if you have it locked into low with selector. It usually would happen on a very steep, curvy, road when you have to let off to get around the curve slower. It shifts up and won't go back into low until you stop and then go again. HPtuner came up with a fix for that and I have that change programmed in now.

Transmissions are very, very susceptible to contamination, particularly particles of anything, so I would not use any cooler that was not only a transmission cooler. If any other product like refrigerant or coolant had ever been through it I would not use. Recored radiators often don't plug the coolers when the tank them and the get full of crap. Even on new coolers I spray a can of cooler cleaner through them to make certain.

In my opinion you will find the same as the rest of did and spend a bunch of time and money doing it, so carefully reading the links, and also searching for other cooler adding threads would be a good idea.

One thing you can do is print out the stock programming chart for the converter lockup and release points. It is by gear and speed for both settings vs tps position. If you keep the speed high enough you can use up to 90% throttle or so with lockup. Unfortunately that speed is somewhere around 50 or 55mph in second gear and many of the curvy climbs prevent you from going that fast so no lockup possible. At least on long climbs on faster roads, like the Eisenhower you can run second gear and lock or 3rd in some spots where you can go fast enough, and you will stay cool.

 

[youngnretired]

Our route 66 trip last year with our radiator and external trans cooler addition didn't yield any trans temps too high except for one long climb with roundabouts thru the process.

I've since added an additional external cooler to the setup and are currently doing an east coast US trip going thru the maritime provinces of Canada and will be home in a couple months. We're going to get some 90F temps in a couple days and will post results when I can. So far, the trans is running cooler under all conditions but it's not been too hot yet so I haven't posted anything yet.

But I will say that the 2 core radiator i installed last year, coolant runs at 194-196 all day, any day, any speed, and any air temperature up to the upper 90s. It will jump to over 200 at a stop light, but as soon as you move, it drops back down.

 

[booster]

It will be interesting to see how you do. Your worst case would be a second gear climb with curves, which might be similar to the roundabouts (you may run into other stuff that will get you too hot that are similar to the roundabout hill, as that is the one that bit us initially and was used for testing after that. I am sure your down the road temps of the trans when the converter is locked, which it will be a lot on level or moderate hill highways, will be cooler than ours because we have a thermostat on ours to hold the temp up in the 175-185* range which is a good place to be, I think, with the DexVI synthetic fluid. Our fall trips will commonly see some cooler temps in 40s or even near freezing some mornings and I just don't like the trans running cold those days.

I don't recall if you have the trans oil still though the radiator or not, we do not and our water temp is a few degrees cooler than yours but not much but will go up at stoplights, particularly if we come off the freeway on a 90-100* day and 75mph and have an immediate stoplight. Might jump to 205* until the thermostat can get back open and we are moving.

 

[TWX]

@booster, any idea where the factory transmission temperature sending unit is located within the fluid loop of the transmission? I was looking at aftermarket sump pans and the PML offering puts an aftermarket sending unit location at the sump. Obviously this would be after the cooling loop. I don't know where the sending unit for the Xgauge code I'm using actually samples from, or even how many possible sending units there are. On my Frontier I can sample both right after the torque converter and after the cooling loop with the factory sending units.

Glancing through your threads, I admit I'm gun-shy about modifying how the torque converter lockup happens, as on a different vehicle that used and entirely hydraulically controlled transmission I burned up the TC lockup clutch after changing differential gear ratios from 2.4 to 3.2 and the lockup was now occurring while the car was pulling hard. The lockup clutch solenoid would then stick in the on position and the lockup wouldn't let go, so stopping was like stopping in a manual without disengaging the clutch. Tearing down the transmission revealed clutch material throughout the fluid.

 

[booster]

The sensor location, based on what I could find out anyway, appears to be in valve body area but I couldn't exactly find out what oil path it was in. This was years ago when I was messing with all this stuff. A number of years later, I put in a pan temp sensor also so I could compare the old school pan temps to the Scanguage temps and it was pretty interesting. There is data listed someplace on the forum but probably in the middle of some other discussion. The temps matched well at steady state going down the road, but under heavy load the pan temps were lower by something like 20* and heated up very, very much faster with the pan lagging by as much as 5-10 minutes depending on the load. That would have me believing that the temp sensor is someplace in the exit flow from the valve body, so closer to what you would get from an exit line sensor in the tubing to the cooler. On a 5 minute super steep, curvy, climb the pan temp would not show anywhere near as high a temp as the internal sensor gives. I think this is where the biggest advantage to having DexronVI in the transmission comes in as it has much higher temperature tolerance so in those instances of high local heat is survives and keeps lubricating where the Dexron IV would either be to thin to lubricate or coking up. The six speeds in the 2010 up years is said to run at 210* on the sensor, probably thermostat controlled and the bet would be all the parts are setup to run at that temp with the DexVI.

Converter survivability was and still is a concern to me, but so far we and others have not had any issues yet. I will have to look up how many miles we have put on ours. Before doing the changes, I went in to several local high performance transmission shops locally and called some national ones also to ask, and although none had ever done that modification to the program because it is an odd thing to address a rare problem, if they had a solid opinion they thought it would not cause rapid failure and probably not long term shortenig of life either. A couple mentioned that the converter with stock programming will lock up at someplace around 3500+ rpm so the shock and wear to the converter would be at higher torque and horsepower generation than at lower rpms so the lower lockups should be a bit less wear per lockup. Of course this also kind of assumes at the lower rpm the transmission is able to generate good lockup clutch hydraulic pressure to lock it quickly and once a trans gets old, that might be an issue. The converters in the 4L80E are often the failure point of the transmission at around 130-150K miles if taken care of, so they are not super robust converters. If we ever have an issue, I will have it rebuilt with improved parts in some parts that are available and with a two or three disc lockup clutch that will be able to handle much more abuse.

The reprogramming is frightening, as well it should be as you can create all kinds of problems if done wrong. No question to that part. My big point on the cooling stuff, is that you can spend a lot of money on other things trying to fix it and only be marginally better. Most that have tried the other stuff don't do the reprogramming and just try to avoid getting into the real bad spots of overheating, which is not always easy, but better than burning up the transmission. We have done pretty much all the other mods to ours and they were certainly not cheap. The only one we didn't do was the underbody installation with full time electric fan on it. I wish we knew where it was actually located and protected as it seemed like a very vulnerable placement to me, and if in cold weather would really need to have a thermostat on it to prevent undercooling if the fan ran full time. You can get to $1K pretty quickly with these changes and way more if you can't do them yourself, so not inexpensive experiments.

 

[booster]

Before you dive in too deep in any of possible improvements, you may want to evaluate how often an overheat might happen. You do live in a hot and hilly part of the country so that gives lots of challenges, I think, depending on where you like to travel.

You didn't mention what speed and gear you were running when the overheat conditions happened so that would be interesting to see where you were in the programming tables relating to shift points and lockup, although you probably were or should have been manually picking a gear to climb in, IMO.

Here is the stock programming I read from our van and was posted in the one of the links. It shows the shiftpoints and lockup points vs speed vs throttle position. From the tables you can tell if you were locked up or not and if it would have even been possible within the limits that the climb steepness and safe driving speed (or speed limit) would determine.

For instance if you were in third gear and speed was 43mph, the max throttle you could use while keeping the converter locked would be 25% tps position. That much throttle wouldn't pull the hill most likely and more throttle will unlock the converter at that speed and gear.

If you were in second gear it would never lock at under 50mph so you could never get it to lock up the converter unless you could speed up to 50 mph and use 87.5% or more tps position. It gets pretty obvious that on steep slopes thast need low gears to get up them you have to be going too fast for most of them to keep from overheating do to being unlocked on the converter.

We did the major programming changes in tow haul only so the normal driving is mostly stock. I did change some minor changes in noarmal based on driving style, but leaving it stock is no issue at all and nothing changes unless you push the tow haul button to do a climb, then you turn it off so none of the potential extra wear and tear happens 98+% of the driving time. When programmed this way, all the other changes we made do make a difference because we still hit short hills that will give a shot of heat but not extreme. The extra capacity cooling takes longer to hit the overheat range so the hill is done before the serious heatup. The changes can mellow them out without selecting tow haul. The drive through Custer State Park in South Dakota is that type of drive and we don't use tow haul there when we go nearly every year. In the midwest there are rarely any climbs that require the tow haul changes. The mountains change all that though.

Long freeway climbs can fool you sometimes unless you know when the converter will be locked. Long, not extremely steep, climbs can sometimes hit a spot where 4th gear will get you up the hill, but you can't go fast enough to lock the converter do to speed limits. Then you heat up. Drive it in 3rd gear at the same speed and you are fast enough and probably have lower tps opein so you will lock up.

 

[TWX]

I'll have to look. Rear axle is tagged as 3.73 rather than 4.10, so that might impact things, but I haven't actually counted teeth or turned the driveshaft with the wheels in the air.

A lot of the speeds we were getting hot in were those same sort of winding mountain roads. At the time I was monitoring on the Scangauge the fuel economy, I have since switched to monitoring gear ratio, and I can see when it's in 0.75 vs 1.00 (ie 4th/OD vs 3rd) so I'll have to do some test driving. I did see it also getting hot when I was on the freeway in fast and very dense traffic and I was eating the exhaust of the vehicles in front of me, but it wasn't getting stupid-hot in that, just around 10 degrees above clean air.

Fortunately we have a city park with a huge mountain in it (South Mountain Park) so I can do some hilly driving testing without having to go very far.

The gear ratio also is giving me pause on tires. I'm still interested in 17" tires with OE wheels but I'd have to stick with LT265/65/17 tires if I want to avoid making the final-drive ratio effectively taller. Those are only available as far as I can tell in Load Range E Load Index 120, same as the 16" tires already on the vehicle.

EDIT: I may also see if it's possible to monitor TC lockup with the scangauge or not.

 

[booster]

I'll have to look. Rear axle is tagged as 3.73 rather than 4.10, so that might impact things, but I haven't actually counted teeth or turned the driveshaft with the wheels in the air.

A lot of the speeds we were getting hot in were those same sort of winding mountain roads. At the time I was monitoring on the Scangauge the fuel economy, I have since switched to monitoring gear ratio, and I can see when it's in 0.75 vs 1.00 (ie 4th/OD vs 3rd) so I'll have to do some test driving. I did see it also getting hot when I was on the freeway in fast and very dense traffic and I was eating the exhaust of the vehicles in front of me, but it wasn't getting stupid-hot in that, just around 10 degrees above clean air.

Fortunately we have a city park with a huge mountain in it (South Mountain Park) so I can do some hilly driving testing without having to go very far.

The gear ratio also is giving me pause on tires. I'm still interested in 17" tires with OE wheels but I'd have to stick with LT265/65/17 tires if I want to avoid making the final-drive ratio effectively taller. Those are only available as far as I can tell in Load Range E Load Index 120, same as the 16" tires already on the vehicle.

EDIT: I may also see if it's possible to monitor TC lockup with the scangauge or not.

I can't imagine why they would have a 3.73 in a heavier than the rest of the Chevies 210. Have you looked at RPO (options) sticker to get the code for the factory ratio? That will tell you what it was from the factor and probably when the computer program is set at.

Your newer Scangauge must have lots more outputs than our older on as gear ratio is not on ours, and neither is lockup or not.

A bit of clarification on the tires and wheels.

Stock tires are 245-75-16 that are about 30.4" diameter and 120 load index. Rear axle and rear tires together is 6048# IIRC

Switching to the wider wheels and using 265-75-16 gives you about 31.5" and a small gear change of about 3% so speedo will likely switch from reading 1.5mph high to reading 1.5mph low (at least ours did). Load index is 123 which is about 370# per tire more load capacity, but no legal capacity just safety factor.

Going to the 17" tires and wheels would use a wide enough wheel and a 265-70-17 which is also right about 31.5" diameter and gives the same error as the 16" bigger tires. The load capacity is 120 on some of them but 123 on others. Our Michelin Defender MS2s are 123 and the same load capacity our 265-75-16 tires were with the extra capacity.

I am super aware of most changes and I could not really detect any change in performance with the 1" larger diameter tires compared to stock, but handling got better with both options of 265 wide tires, IMO. You are talking about the same as a gear change of 3.73 to 3.83. But first you need to figure out what gears you have. You might need to jack up a rear wheel and count driveshaft vs wheel revolutions, just remember wheel revolutions will be double the ratio with one wheel on the ground and an open differential.

If your van is built on a 2007 chassis like our 07 is, it could have had a bad rear axle from the factory as they had a run of them that had bad housings. Ours ate pinion bearings twice in the first 20K miles so we just changed it out to a 10.5" ring gear full floater with Gov-loc. If yours had a bad one you probably have a salvage yard used one as 4.10s can be hard to find even in the smaller rear axle. Check the manufacture date on the door sticker from GM to see the manufacture date of the van and also look at the rear axle white sticker that should have the axle manufacture date on it.

 

[TWX]

I decoded the RPO codes and they claim I should have a 4.10 axle, full-floater. But the axle in the van itself has a 3.73 tag on it and is definitely not a full-floater.

Speedo already reads lower than I'm going, around two miles per hour at 60. Probably not enough to get a ticket if I don't speed but still mildly annoying.

Mine's on an '05 chassis.

As for the Scangauge III, it's totally worth it. One can manually enter codes onto it through the touchscreen interface.

 

[booster]

I decoded the RPO codes and they claim I should have a 4.10 axle, full-floater. But the axle in the van itself has a 3.73 tag on it and is definitely not a full-floater.

Speedo already reads lower than I'm going, around two miles per hour at 60. Probably not enough to get a ticket if I don't speed but still mildly annoying.

Mine's on an '05 chassis.

As for the Scangauge III, it's totally worth it. One can manually enter codes onto it through the touchscreen interface.

How are you determining if it is a full floater or not? AFAIK, and I just checked by looking at our factory service manual for 2007 and it shows no code for ring gear size or full or semi floater just codes for options that don't directly say the size of the axle. I can't imagine anyone being foolish enough the change out a very good full floating axle for a much weaker semi floater when they could just change out the gears to 3.73 if that is what they wanted. These days a full floating 10.5" Dana 70s with govlock locker with 4.10s, that is for express vans is worth gold compared to the 3.73 used ones.

If it says you are going slower than actual speed it could be the gear change, but that should be about 10% off so they must have reprogrammed the PCM when the change was done.

 

[youngnretired]

A couple thoughts for those who read this in a similar situation:

If you radiator is original, it's 21 years old and probably 80-90% efficient with rocks and junk on the outside blocking airflow, and possibly some deposits on the inside coolant cores. Simply changing the radiator for new may help, even if not going to an upgraded 2 row style.

Changing the radiator also gets you new oil and transmission coolers in the radiator tanks. Those do fail and you wipe out the transmission when they do. Yours are 21 years old.

The fan clutch may be at the end of its service life and probably should be changed as it may not be fullly locking up and moving maximum air.. While you're that far under the hood, change the water pump too as it's only a few more bolts to do it and all the work to get at it is done.

Our transmission seems to run 5-10 degrees cooler without the AC on. So that tells me that there is a fair amount of cooling for the transmission from the cold side of the radiator, which isn't as cold when the AC is on elevating the ambient air temperature of the air flowing thru the radiator.

 

[TWX]

How are you determining if it is a full floater or not? AFAIK, and I just checked by looking at our factory service manual for 2007 and it shows no code for ring gear size or full or semi floater just codes for options that don't directly say the size of the axle. I can't imagine anyone being foolish enough the change out a very good full floating axle for a much weaker semi floater when they could just change out the gears to 3.73 if that is what they wanted. These days a full floating 10.5" Dana 70s with govlock locker with 4.10s, that is for express vans is worth gold compared to the 3.73 used ones.

If it says you are going slower than actual speed it could be the gear change, but that should be about 10% off so they must have reprogrammed the PCM when the change was done.

The axle doesn't have the bolts on the hub that would allow the axle to be removed without removing the bearings and hub.

I have such an axle in my '82 Dodge D350, so I'm familiar with the differences.

it's 21 years old

I have a set of maintenance records from the previous owner, I'll have to go through them more thoroughly. I do know that he had to have transmission work done but I don't know if he replaced it. I do know that there was rear end work done but I don't know the extent. I do know that shocks are new and there are lift-blocks and it looks like the springs are newer than the van. If the rear end got cooked for some reason then it might've been replaced with what was handy, or else for some reason somehow I'm getting the RPO code wrong.

 

[booster]

A full floater will have the hub protruding through the wheel opening a few inches and have a thick cover on the end of the hub with large bolts holding it on. You say yours doesn't have that cover? The semi floater will have just the axle flange with the lug studs outside the wheel as they don't use a hub because they use the axle housing to hold the wheel bearing. This is a Dana 70, the header said so not the exact model the vans used but the appearance is the same and looks just like our 10.5" Dana 70s full floater.

It is starting to sound like there was some kind of accident that did a lot of damage in the rear axle and drivetrain areas. Transmission work, odd rear axle that looks crooked plus other new parts.

If the van had a 10.5" rear axle full floater it would carry and RPO code G80 which doesn't define the axle size but says it has a govlock locking differential. Only the 10.5" full floater ever came with the govlock so has to be. It would also probably have an RPO code Z82 which is the trailer tow package and included the big axle and a factory add on trans cooler in front of the radiator which you haven't mentioned IIRC. As far as I know that is the only way to know from the RPO codes. If it had a 4.10 originally the RPO code will be GT5 and if it was 3.73 it would be GT4 regardless if it was the small or large axle.

Does the axle have a white sticker on the rear of the driver side housing tube of the axle facing the rear? If so it should say the manufacturer, date, model number and ratio of the axle. If not look at the side of the differential to see if it says Dana on it. The Dana should also have a cast steel differential cover on it, not a sheet metal one as it is structural. Also check to see if the pinion is bolted in from the front of the housing which would say it is a American Axle (commonly called GM corporate by many) axle.

You have something very odd going on there I think.

 

[Bangorbob]

Welcome to the high temp club. I've been following for a couple years now. My question to booster is: It's fine you give a lot of data, but how do you go about reprograming shift points? What is needed? Who can do it?

 

[booster]

Welcome to the high temp club. I've been following for a couple years now. My question to booster is: It's fine you give a lot of data, but how do you go about reprograming shift points? What is needed? Who can do it?

The tools to do the changes are available, but not inexpensive. Looking back, the tuner was actually less cost than the total of all the other cooling stuff I tried. The other stuff does help some also, especially where the extra cooling is needed and reducing that heat isn't possible with the tuning so not wasted monely. It is basically using the same "tuner" that folks use to reprogram the PCM on a hotrod or diesel with deletes added. The software runs on a laptop which you can change almost all the engine and transmission parameters.

AFAIK, all the ones on this forum that have done the changes did there own at home. Two used the our programmed settings as an easier starting point as I could just send them a file with a completer reprogram on it to load to their laptop and vehicle. Both changed a few things to suit their driving style and needs, and were happy with the results.

Many hotrod "tuner" high performance could do the changes, but I have talked to a couple that I know and they have never done that kind of a task, as it going for better cooling instead or raw power like they normally do.

You might find a private individual that would help out and do it reasonable inexpensively if they already had the tuner. Car clubs and hotrod truck clubs and shows would be the place to look or it could be a neighbor or relative even.