Express Van Upgrade Cooling System With a 2 Row Radiator

[booster]

Fluid flow speed is one of the parameters they use to design cooler systems that are liquids and too fast can be a thing that can happen, but too slow is also bad. The transmission flow is really quite low and I was surprised how low. I think it was rated at something like 1-2 gpm at low rpm. IMO the big advantage of parallel coolers is restriction reduction, but they also have to match very closely in the total restriction from the cooler, lines, fittings etc so they both share the flow equally.

The calculations of heat transfer for vehicles is probably pretty complicated with varying aiflow, varying fluid flow, varying ambient temps, and varying heat input and on a moderate 70* day you can see running temps from 130 to 230* depending on conditions. All of this is why I choose to add thermostats to our systems most of the time, to limit the range the oil has to deal with. I think a lot of the newer transmissions do this also as the 6L90e in the later vans all seem to run over 200* all the time per the inputs owners have given.

 

[youngnretired]

A final post on our route 66 trip from Chicago to Santa Monica and an equipment update. The trip took 63 days, 10,216 miles, 4 nights in motels (2 were historic and 2 because they were the same price as an RV park), 25 nights in RV parks or campgrounds, and 34 boondocking. Averaged 13.28MPG and only had a couple minor issues that needed to be taken care of while on the trip. We really enjoyed boondocking in the the areas that we found, and especially the western parts of the country.


The radiator and fan clutch performed as expected, however, the transmission ran a little warmer than I had hoped for. As others posted, that factory style external cooler doesn't seem to do much, and it may only knock the high spots off, but we've never owned a van, nor a vehicle as heavy as this before either. I only had a scangauge and ran the van around town for 1 day to gather data before I embarked on the cooler and radiator changes. So I had very little factory stock data before this trip. A lot of valuable information was learned on the trip though. In most situations, the transmission runs at 90-100 degrees above ambient temps, excluding climbing hills. As we got into colder temps closer to home, the transmission actually runs at 110+ degrees above ambient when the air temp was in the 30s and 40s. As booster has commented, the torque converter lockup is crucial to transmission temps. Climbing hills where I could keep the converter locked, no problem, but when we'd start climbing with an unlocked converter, the trans temps started climbing. This spring I'll work on changes to the external cooler setup and see how that goes hopefully before the next trip. We're looking at an east coast trip into Newfoundland and Labrador Canada areas next year, so the learning will continue on that trip but that area of the world is pretty flat compared to the western US.

Thanks all!

 

[Bangorbob]

Thanks for the update.

 

[booster]

A final post on our route 66 trip from Chicago to Santa Monica and an equipment update. The trip took 63 days, 10,216 miles, 4 nights in motels (2 were historic and 2 because they were the same price as an RV park), 25 nights in RV parks or campgrounds, and 34 boondocking. Averaged 13.28MPG and only had a couple minor issues that needed to be taken care of while on the trip. We really enjoyed boondocking in the the areas that we found, and especially the western parts of the country.


The radiator and fan clutch performed as expected, however, the transmission ran a little warmer than I had hoped for. As others posted, that factory style external cooler doesn't seem to do much, and it may only knock the high spots off, but we've never owned a van, nor a vehicle as heavy as this before either. I only had a scangauge and ran the van around town for 1 day to gather data before I embarked on the cooler and radiator changes. So I had very little factory stock data before this trip. A lot of valuable information was learned on the trip though. In most situations, the transmission runs at 90-100 degrees above ambient temps, excluding climbing hills. As we got into colder temps closer to home, the transmission actually runs at 110+ degrees above ambient when the air temp was in the 30s and 40s. As booster has commented, the torque converter lockup is crucial to transmission temps. Climbing hills where I could keep the converter locked, no problem, but when we'd start climbing with an unlocked converter, the trans temps started climbing. This spring I'll work on changes to the external cooler setup and see how that goes hopefully before the next trip. We're looking at an east coast trip into Newfoundland and Labrador Canada areas next year, so the learning will continue on that trip but that area of the world is pretty flat compared to the western US.

Thanks all!

Your are very closely tracking with what we found in our development process, which is not surprising at all to me. I also think you may be able to improve the situation with more trans cooling, if it is good enough depends on how extreme the climbs you do get to. If you are on climbs that have safe speeds high enough that you can use a low gear and lots of rpm you will be able to stay locked on the converter and run cool enough. If the speed limit is too low to use even second gear to get enough speed to lock the converter (it locks on speed not rpm) you will run hot and have nothing you can do about except stop and let it cool off. Big coolers and fans can delay that overheat, but not eliminate unless you have a huge cooler with it's own fan and even that may not do it.

I would point you back to this chart which is the from out stock 07 Chevy concerning TC lockup points

It shows that in second gear, when you get near full throttle like is needed to climb hills, the converter won't lock until 50 mph so if you are on a curvy 35mph max steep climb there is absolutely no way to get the converter to lock up. It is impossible AFAIK to get the converter to lock in first gear.

The other thing you will run into is on the super steep stuff that require low gear just to move. The program in my opinion is bad on this because in the 1 position it will still shift to 2nd gear at low throttle points. If you let off the gas in a sharp curve all of sudden you are in 2nd gear and not able to pull the hill and it won't go back to 1st until you stop. It is now possible to reprogram that part also, but it wasn't when I started all this stuff. Ours is reprogrammed now.

 

[youngnretired]

I'm admittedly reluctant to reprogram transmission shift points, and certainly don't have the tool to do it. There were times when all I wanted was it to unlock the converter in 4th, but it would drop to 3rd and unlock. A few times I was able to get creative and instead of slowly pushing the throttle, I'd blip it to hopefully get it to unlock and stay in 4th. But in general, for someone who pays attention to transmission gear, throttle position, vehicle load and generally what's going on etc, I think a lot of GM vehicles could shift a whole lot better than they do. I'm sure there's a million things going on behind the scenes that make it more difficult than what I think it is, but I'll leave that up to the original engineers.

 

[dicktill]

I'm admittedly reluctant to reprogram transmission shift points, and certainly don't have the tool to do it. There were times when all I wanted was it to unlock the converter in 4th, but it would drop to 3rd and unlock. A few times I was able to get creative and instead of slowly pushing the throttle, I'd blip it to hopefully get it to unlock and stay in 4th. But in general, for someone who pays attention to transmission gear, throttle position, vehicle load and generally what's going on etc, I think a lot of GM vehicles could shift a whole lot better than they do. I'm sure there's a million things going on behind the scenes that make it more difficult than what I think it is, but I'll leave that up to the original engineers.

Considering how much effort you put into your cooling system, reprogramming the shift points would be a piece of cake for you. Of course, when I did it, I had the pleasure/luxury of @booster slow walking me through it all! I have mine programmed a bit differently than his, both because his '07 and my '10 have different computers, but also because of differences in personal tastes. Anyway, the results were well worth the effort.

 

[booster]

I'm admittedly reluctant to reprogram transmission shift points, and certainly don't have the tool to do it. There were times when all I wanted was it to unlock the converter in 4th, but it would drop to 3rd and unlock. A few times I was able to get creative and instead of slowly pushing the throttle, I'd blip it to hopefully get it to unlock and stay in 4th. But in general, for someone who pays attention to transmission gear, throttle position, vehicle load and generally what's going on etc, I think a lot of GM vehicles could shift a whole lot better than they do. I'm sure there's a million things going on behind the scenes that make it more difficult than what I think it is, but I'll leave that up to the original engineers.

I am guessing, but looking at the program and in particular the tow/haul vs normal programming (the tow/haul) moves the shift points and lockup up to even higher speeds), I think the engineers/programmers were primarily worrying about pulling power, not transmission temperature. To me a touch extra acceleration is pretty useless if you are sitting by the side of the road oveheated.

Dicktill and a couple of others have also reprogrammed their vans and are satisified AFAIK, and I am pretty sure every one is different because of driving style and taste. Dick not only has a different year, but also a 4.8 rather than a 6.0 so that also makes a difference.

A speed shop or custom truck place can do the programming if you tell them how you want it get a copy of one the ones the rest of us have done. Not sure what it costs now, but back when I did ours it was hardly more the $100 if you had a program and just needed it put in or a simple thing like speedo calibration to match a gear change or tire size change. The changes can be done just in tow/haul so you still can keep you factory programing in place.

 

[Bangorbob]

Booster, I have this thread probably 5-6 times and I don't quite understand the programming. When you say Get a copy of the ones the rest of us use. How do I get it?

 

[booster]

Booster, I have this thread probably 5-6 times and I don't quite understand the programming. When you say Get a copy of the ones the rest of us use. How do I get it?

All of this is more in language of hotrodders than RV folks, so not surprising.

The vans like all vehicles now days has a power control computer that tells the engine and transmission what to do. All of them have a "program" or "tune" as it is commonly called that sets all the data points for fuel, spark, cooling, etc in the engine and thinks like shift points and converter lockup for the transmission.

The cool thing is that you can get a little interface unit and some software for a laptop that will talk to the vehicle computer so you can read out all the settable parameters for that vehicle and then load those parameters into the laptop software where you can see, and even better, change them to what you want. You then copy them back out of the laptop into the vehicle and whatever you changed will be changed in how the vehicle runs and drives.

In this case, I worked only on the transmission settings to modify when the torque converter was in lockup as when it is unlocked in generates a LOT of heat into the fluid. Since when you lock the converter it doesn't boost torque anymore, you also have to move the shiftpoints to allow for that by putting yourself in the right gear and rpm to be able to pull the load.

Yes, it does require knowledge of how it all works, how it programs, and what you need to be careful of to prevent damage.

The copy I refer to is that the programming for one engine can be put in a different engine of the same style, so a flash drive with my programming in it can be loaded into your software and then into your van for instance. A lot of it is the need to understand the compromises you might need to make to get the benefit you need, but the good it you can put the changes only in Tow/Haul mode so it won't effect daily driving when you don't get hot.

Not hard to do once you know how and most of the users here that have done the changes, usually a copy of mine but with their preferences also, are old school racers or hotrodders and some even already had the communicator and software and knew how to use it.

For the one time user going to a speed shop and hiring it done might be the best thing to do, as they would know how and have the equipment to it, and also would be able to read one our our programs to see how and why it was done. They work on speed and horsepower stuff and have never heard of reprogramming a transmission for heat reduction.

 

[youngnretired]

It is now 1 year later after I put this post together and we just returned from a 2 month trip to the east coast of the US and Canada thru Newfoundland, Labrador and Quebec and have an update. Before embarking on our trip this year, I added an additional transmission cooler, mostly because I felt that running down the road with a 180 degree transmission temperature and 90-100 degrees above ambient temperature was a little high. I'm not a professional mechanic nor did I ask any professional for their opinion, it's my belief that 180 is too warm.

For an additional cooler, I chose another tube and fin style cooler, similar to the factory original external cooler, only from the belief that they have less restriction in the fluid flow thru them compared to fin and plate type coolers. I have no proof of this, but I didn't want to add a lot of pressure resistance to the transmission cooler loop by running thru too many tubes and plates etc and causing flow issues because of a poor design. Plus, tube and fin coolers are also pretty cheap, and they do work.

After looking thru several sizes of Hayden coolers, I chose the 403 ultra cool tube and fin radiator as I felt it would be the right size for additional cooling.

Amazon.com

For the install, I used the insulated pipe type hangers to mount the cooler at the top of the radiator support. I used these in the past with other installs on older cars and never had an issue. While going to the pick and pull yard last year seeking data on how the original external coolers were plumbed and installed, I had cut off sections of transmission lines because I originally had wanted to install two factory type external coolers using the factory type quick connect fittings, but realized after having both of the external coolers here that it wasn't realistic that they would fit in the space without issues. So I cut one of those transmission lines shorter to have a 90 degree bend in it and flared the end to better hold the rubber line to the tube. Since we were going to the east coast, I didn't know what temperatures we'd encounter nor how cold the transmission would run. I wanted the setup where I could easily remove this additional cooler from the loop if we experienced too cool or a condition and simply re-snap together the fittings to use only the factory style external cooler. I could have also removed the grill and fashioned some cardboard to cover this additional cooler if needed. We never had to do this and all was fine.

Where the cooler hung from the upper radiator support, it happened to be a little further back from the factory external cooler, so this additional cooler tucked just behind the factory cooler location.

After 10,000 miles on the east coast and depending on conditions, this setup seems to run at 75-85 degrees above ambient temperature, and transmission runs between 145-165 degrees while going down the road with 55-85 degree ambient temperatures. This setup does take a while to warm up in the morning depending on your speed and conditions, but once it gets to temperature, it pretty much stays in this range. I would also NOT go any larger cooler. When we first left town, south of Chicago we drove thru very heavy rain for 5+ minutes and the transmission dropped to 125 degrees. I don't know if this was due to a drop in air temperature or rain getting on the cooler and we were probably only doing 45 MPH on a 2 lane road. While on this trip, there were more hills than I expected there to be. With ambient temperatures in the mid 70's pulling grades, transmission temperature reached the 180's probably 8-10 times, and up to 194 degrees twice with a longer 2nd and 3rd gear pulls up the grade.

 

[booster]

What you are referring to about not wanting a bigger cooler is why I always recommend using a temperature controlled thermostat in any and all aftermarket cooler installs unless in hot climates. Overcooling can be an issue. In your case, 125* degrees would not be an issue, IMO, especially if it Dexron VI fluid in the transmission ( I think all the Chevies should be switched to Dexron VI). 2007 was the first year GM recommended it and started putting into new production vans with the 4L80e transmissions. I like the smaller version of the Improved Racing thermostat as it has less bypass flow, is smaller, and still uses a wax pellet to control temps. You can change the pellet to 145*, 165*, and 180*. We like the 165* one as it gives an internal temp of about 185* most of the time and gives full flow a bit sooner. I have our van out that has huge cooler capacity and no radiator heat at 20* and a bit lower, and it held about 120-140* which is just fine.
Did you hit any non lockup conditions on your trip during long climbs? My guess is probably not or you would have gotten much hotter than you did.

 

[youngnretired]

More than likely we're not going to run our van in really cool temperatures, except maybe to get south enough during winter months, so I didn't want to add a temp controlled bypass valve at this time. And if I know we're leaving town when it's too cool out, I can always cover the additional trans cooler. It takes but 5 minutes to get the grill off an express van, including the time to go get the tools.

I would like to monitor temperatures in the cooler lines at all points (going to radiator, going to factory style external cooler, going to newly added cooler, and return to the transmission), to see how those compare to the temperature listed on the scangauge. With that said, I'm probably not likely to mess with this any further as it's accomplished my goals, given it's design limitations, but for 99% of what we're going to use the van for, this has taken care of my concerns and under most circumstances, taken care of overheat and limp mode times (which we've not experienced yet).

The two times we got to 194 degrees were during 2nd and 3rd gear non-lockup periods and likely during the times getting to the mid 180's as well except some of that may have been in 4th gear non-lockup. If you start climing a hill at 155 trans temp instead of 180 as we did last year, you've got more headroom before the trans starts to get too hot. Last year max temp on the one hill climb was 217 degrees. Given the same conditions but starting from a trans temp of 155 degrees, that theoritical max temperature from last year with the additional trans cooler would then have been 192 degrees, very similar to what we experienced this trip.