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Old 09-11-2019, 12:37 AM   #401
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Originally Posted by Rulebreaker
Booster, thanks for this wealth of information! Very much appreciated!

Front:
I'd be interested in your opinion on the merits of the Moog 18004 vs the Husky SC20470. It seems the 18004 is constant rate while the SC20470 is progressive? Might this translate into smoother ride on the SC20470 at the expense of reduced vehicle height versus the 18004? The Husky seems to be listed as a constant rate where I looked and a cross for Moog 81006 which is shorter than the 81004 most have used in post 2002 models. You would have same rate but less length and lift. I don't like variable rate for constant heavy loads because the softer coils are over worked.

If I decide to seek additional height later using 3" spindles as some have done, would both of these springs likely still work for me? Some have done OK with them and some have not. Personally I don't like knuckle lifts because they mess up the suspension and steering geometry, and I can always feel it. I am pretty particular in regards to steering, others not so much.

Rear:
Is it just the adjust-ability of airbags that you prefer over using additional springs? For me, vehicle loading is pretty constant and we don't tow anything, so no trailer tongue weight to consider. (I'm just trying to rationalize the added cost and complexity vs. the benefits.) As for type of airbag; it seems some have used Firestone, while others chose Air Lift. Integral bump stops within seems to be a worthwhile feature. Is there a particular make and model of airbag that you recommend? Adjustability is nice, but most have found they ride a bit better also, but some claim worse. We are currently running ours the stock springs with the overload leafs removed. It really improved the ride, but there is only one other van doing the same and was just recently done, so not ready to say for sure good to go yet. With the overload out, we need to use bags with built in bump stops in case a bag pops as the bags sit where the original bumps were on the axle. Firestone bags would not need the internal because they are not mounted on the axle. I prefer the Airlift as they are larger diameter so less pressure plus they put the load directly on the axle tubes rather than on the lower spring bottom plate. Neither brand is bad IMO.

Shocks:
Bilstein B6-24-187435 front and B6-24-221948 for the rear seem to be the shocks of choice. Your thoughts? I gather if I decide to pursue 3" spindles for additional lift later, these B6 shocks might be too short? True? Knuckle lifts usually leave the lower control arm in the stock location and would use the same shocks, AFAIK. If you go more than about 3" up with springs, you will need longer shocks most likely.

Rear Sway Bar:
Vehicle has an under-hood generator (rather than under vehicle) so a Hellwig sway bar should work.

Overweight Vehicle, Wheels, Tires, etc.
Yep, vehicle is definitely overweight by about 3%, so I'll look at what I can do to lighten it. I do have aluminum wheels, so the offset issue you mentioned applies. Tires still have lots of tread, but when they're due for replacement I'll definitely look at upgrading wheels and tires to provide more load capacity.

As for front tire pressure; it seems 50psi is what's recommended on the vehicle nameplate as well as on Bridgestone load tables at the 2,050lb load per tire I have. I understand 210s tend to be lighter in the front than 190s due to the overhanging weight at the rear. Is the move to 65psi in the front, (presumably to improve handling and ride quality and to reduced heating and rolling resistance) likely to cause uneven/excessive tread wear in the center of tires over time due to crowning? It appears the plates are the stock ones or copies of the same pressures, and would be inteneded to cover an empty or full van without changing pressure. The 50psi squeeks in capacity at full load and would ride decently at low load, so a compromise on both ends. The 65psi is what most have found to be the best mix of steering response and tracking vs ride quality. Some like less, a few like a bit more. The tires will run cooler and wear the edges less at 65psi in most cases. Be aware you may have more weight on one side than the other by a couple of hundred pounds so splitting an axle weight can be a bit off.

Recently I measured ground clearance on my rig to the fresh water tank drain valve and it was a measly 4-3/8", so I'm definitely looking forward to gaining some additional clearance from these mods. Very believable at your weight. Probably low point right at the fragile tank valves and macerator, like we had.

Cheers,


Brian
I have the other van that is modified similar to Booster's: same airbags & overload springs removed, and both have large rear swaybars, albeit slightly different. Main difference is that I have aluminum spacers (replacing the overload leaf) on both sides, while Jim has only one side done. I may have to copy him on that too as I have a (small) constant pull to the right. So far we have about 750 miles on it and the handling and ride are great! (at least for a Chevy van, far better than stock methinks)

Regards, Dick
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Old 09-11-2019, 01:07 AM   #402
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I have the other van that is modified similar to Booster's: same airbags & overload springs removed, and both have large rear swaybars, albeit slightly different. Main difference is that I have aluminum spacers (replacing the overload leaf) on both sides, while Jim has only one side done. I may have to copy him on that too as I have a (small) constant pull to the right. So far we have about 750 miles on it and the handling and ride are great! (at least for a Chevy van, far better than stock methinks)

Regards, Dick

I will expand a bit on the spacer to replace the overload leaf that is put into the stack like overload but just is a spacer. Dick used two to replicate the stock van spring height from the axle, which I also would have done, except I wanted to see if I could compensate for the fact that ours, and most other Chevies, required more bag air pressure on the driver side to sit level. To put more of the weight onto the leaf spring on the driver side only, I used the spacer on that side only. It did make it so our air bag pressures are even now when level.


I think all of this is because the driver side rear carries several hundred pounds more weight than the passenger side. The problem comes with the rear axle being rated at 6080# which is exactly the same as the tire rating of 3040# X 2. You get into a condition that if you are at max axle weight but have more on one side, that tire will be overloaded. It appears GM modified the spring or mounting to take some weight off the driver side, which transfers that weight to the passenger rear and driver front wheels. This resolves, for the most part, the possibility of overloading the driver side tire.


We are approaching 10K miles on our van with the overload removed and haven't had any downside issues to this point, but do have improved rear ride.
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Old 09-17-2019, 02:13 AM   #403
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Thanks all for your input.

Moog cannot confirm the suitability of their 81004 for my 2018 Chevy Express 3500 (their tables only go to 2006 model year) and suggested I contact Coil Springs Specialties (CSS) in St. Mary's, KS. Based on Chevy's part number for my stock front coils (20760345) they engineered a spring set to provide +2.50" trim height. These springs would have about 17.75" free length and spring rate of 1,645#/in (vs. 1,570#/in for the 81004). Price would be about $330/pair for their coils (incl. shipping) vs $257 for the 81004.

I'd be interested in peoples' thoughts on:

1) compatibility of the 81004 in my 2018 Express 3500
2) the merits of the proposed CSS coils vs the 81004
3) any experience with / reputation of CSS as a spring supplier (Anybody had experience with CSS? How did things work out for you? Would you use them again?)

Thanks, Brian.
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Old 09-17-2019, 03:18 AM   #404
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Thanks all for your input.

Moog cannot confirm the suitability of their 81004 for my 2018 Chevy Express 3500 (their tables only go to 2006 model year) and suggested I contact Coil Springs Specialties (CSS) in St. Mary's, KS. Based on Chevy's part number for my stock front coils (20760345) they engineered a spring set to provide +2.50" trim height. These springs would have about 17.75" free length and spring rate of 1,645#/in (vs. 1,570#/in for the 81004). Price would be about $330/pair for their coils (incl. shipping) vs $257 for the 81004.

I'd be interested in peoples' thoughts on:

1) compatibility of the 81004 in my 2018 Express 3500
2) the merits of the proposed CSS coils vs the 81004
3) any experience with / reputation of CSS as a spring supplier (Anybody had experience with CSS? How did things work out for you? Would you use them again?)

Thanks, Brian.

Hard to tell much from that information, I think. The 17.75" fee height is the same as the 81004 and factory springs so would go in without a compressor..


The problem comes in at what are they referring to at +2.5" trim height? Our 07 factory service manual gives a trim height at 4.3" in an unloaded van. Most have found that a spring like the 81004 give that same 4.3" trim height in a Chevy with near max of 4300# on the front. Stock springs are about 2" below that when fully loaded. Trim height per GM is measured under the van and is the distance from the pivot point on the frame of the lower control arm to the bottom of the lower balljoint.


Knowing what the spring wire diameter is and an the number of turns would give somewhat of an idea of how they compare. The springrate difference is not huge and they two springs could perform very similarly..


We have seen quite few 81004 springs put into Chevies later than 2006, and AFAIK, nothing has changed to this day to make it not work still.


No information that I have ever heard on CSS.
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Old 10-10-2020, 03:04 PM   #405
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I am in the process of having Moog 81004s installed in 2006 P190 but my shop is telling me my Bilstein shocks are not long enough. I was at 33.5" before and now measure 37" with new springs installed. Have others had this issue and if so specifically how was problem resolved? Currently shop is planning to fabricate shock extensions.

Thanks
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Old 10-10-2020, 03:19 PM   #406
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Shorter Moog coils are available. Might be a better option than shock extensions ? ? :
Moog 81008, 81006, 81004
Moog 81004 to 81012.JPG
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Old 10-10-2020, 03:29 PM   #407
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Originally Posted by Mrchannman View Post
I am in the process of having Moog 81004s installed in 2006 P190 but my shop is telling me my Bilstein shocks are not long enough. I was at 33.5" before and now measure 37" with new springs installed. Have others had this issue and if so specifically how was problem resolved? Currently shop is planning to fabricate shock extensions.

Thanks

That is about what everyone is getting with the Moogs now, which IMO is too much for a spring lift, but many have been OK with the results.


If they fabricate shock extensions they have to be very careful about how long they make them. If they make them long enough to put the shocks in the best place, with about 2" of downtravel, it very, very likely that the upper control arm will start hitting the frame on downtravel, as the shocks are the stop. No rubber bump stop on downtravel like on up travel. Most of the information I have seen says you need at least 1/4" at the arm to frame point at full extension as it will actually move further in use because of the rubber shock bushings. If they go to the 1/4" point, you will be OK that way, but with less than desirable downtravel which may cause topping out the shocks regularly. We have heard of lots of failures of shocks to this point, but there aren't a lot of installs with the newer, stiffer 81004s yet. The front suspension is also going to get more positive camber progressive under bump conditions, which may make the van pitch or dart to one side on single wheel bumps or cause a steering wheel shudder or feedback. Tire wear on the ouside edges will probably increase some also.



Just yesterday I was searching to see if I could find a tall upper balljoint fo for the Chevy vans, and have not to this point. That would certainly help the situation as they are normally about 1" taller for stock type installs. I have also not found any upper balljoint spacers for vans to this point, but some pickup ones might be the same.
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Old 10-10-2020, 07:18 PM   #408
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Default 81004 shock extensions

Spacer was installed at base of shock to provide travel.
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Old 10-10-2020, 07:48 PM   #409
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Spacer was installed at base of shock to provide travel.
Good idea on the spacer. Do the bolt threads have full length engagement? Hard to tell from the picture.
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Old 10-10-2020, 10:29 PM   #410
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Good idea on the spacer. Do the bolt threads have full length engagement? Hard to tell from the picture.

It appears that they moved the shock to the upper side of the mount and added a spacer besides to get more travel. When I put ours on top, it would contact the frame with the upper arm when in full droop.
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Old 10-11-2020, 10:47 AM   #411
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It would be nice to get this front spring issue sorted out.

Maybe the next forum member to make the change could measure the coils before installing to report if any change there.

Also, it should be useful if someone would report before and after "Z" height measurements. If the van gets to 37" wheel well height is it still within the Z trim height specifications? Is it important to be within the Z trim height specifications? Are the installers even checking that?

The 81006 coil is approx 5/8" shorter than the 81004 coil. Would the 81006 coil be a better choice?

Two images attached:
Moog 81004 to 81012.JPG

Moog 81006 vs 81004.JPG


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Old 10-11-2020, 11:47 AM   #412
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Originally Posted by markopolo View Post
It would be nice to get this front spring issue sorted out.

Maybe the next forum member to make the change could measure the coils before installing to report if any change there.

Also, it should be useful if someone would report before and after "Z" height measurements. If the van gets to 37" wheel well height is it still within the Z trim height specifications? Is it important to be within the Z trim height specifications? Are the installers even checking that?

The 81006 coil is approx 5/8" shorter than the 81004 coil. Would the 81006 coil be a better choice?

Two images attached:
Attachment 10645

Attachment 10646


---------

Good points. I agree on the 81006 test is someone chooses to do it. I think I also mentioned in it in one of the previous discussions on this a while ago, as it is about the only thing left to try. Maybe an 81006 and a spacer would be needed.


It would be relatively easy to check the difference of the Z trim as IIRC at 2' of lift with a 33.5" wheel well starting point ours was right at recommended trim height on stock tires. Z trim changes the same as the wheelwell as long as both sides are up the same so the OP would be 2.5" about the recommended Z height. I will have to dig out the spec in my factory service manual to see if that is within range but I think it is quite a ways over.


Our dimensions are somewhere earlier in this thread I think, but hard to find also, I think, because it is so long a thread.
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Old 10-11-2020, 04:23 PM   #413
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I just looked up the Z trim height for our 07 Chevy 3500 Roadtrek in the factory service manual.


It shows a range of 4.0 to 4.5" with a preferred of 4.3", so quite a small range.


If our van really was right at 4.3" when the wheel openings were 35.5", that would put the 37" height of the van at 5.8" and way out of recommended range. Of note is that they show the 1500 and some 2500 vans higher, but those are likely the torsion bar suspensions which use different control arms.
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Old 10-20-2020, 02:36 PM   #414
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Good idea on the spacer. Do the bolt threads have full length engagement? Hard to tell from the picture.
Regarding the "full length thread engagement" I hope yes. I am pretty sure the bolts are original so assuming there was an extra 3/8 inch then it should be good.
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Old 10-20-2020, 02:59 PM   #415
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It appears that they moved the shock to the upper side of the mount and added a spacer besides to get more travel. When I put ours on top, it would contact the frame with the upper arm when in full droop.
Good information Booster thank you. I will be replacing the control arm bumpers in the next few days so will be able to look at suspension in full droop. Not sure i completely understand your description but hope it becomes apparent when on the jacks. So far I am not unhappy with the ride and handling.
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Old 10-20-2020, 04:24 PM   #416
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Good information Booster thank you. I will be replacing the control arm bumpers in the next few days so will be able to look at suspension in full droop. Not sure i completely understand your description but hope it becomes apparent when on the jacks. So far I am not unhappy with the ride and handling.

I know there are pix on this site of the contact area for the frame and control arm, possibly in this discussion. Also could be in any of the other lift discussions, I will see if I can find them.
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Old 10-20-2020, 04:37 PM   #417
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Here is a pic that is close. I think this is for a pickup which is a bit different but has the same issue. On the van the control arm sits on top of the frame and the edge it hits is as big as this in the pic. The location if the same area though. This on is right on the frame contact.




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Old Yesterday, 12:26 AM   #418
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Default UCA Droop Stop with 81004s

On full droop the control arm does hit the stop. With weight on the wheels I have more than enough room for a finger between the arm and stop. What are the risks associated with this situation?
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Old Yesterday, 12:45 AM   #419
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On full droop the control arm does hit the stop. With weight on the wheels I have more than enough room for a finger between the arm and stop. What are the risks associated with this situation?

The problems come with a big hole in the road or whoopy do type thing and highway speed. Basically, anything that causes the wheel to into full droop while carrying the momentum of the wheel and tire weight plus being pushed by the spring force.



The pickup truck sites state many cases of bent upper control arms if contact is allowed to happen. It would be interesting to see how much downtravel you actually have before it hits, as you are sitting very high with new springs. If you have lots of downtravel, you MIGHT get away with allowing the arm to be able to hit the frame, but it would still be possible.


An alternate solution to getting shocks that match your actual travel, which can sometimes by hard to do, would be to put on a downtravel limiting strap to stop the downtravel before the arm hits the frame.
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Old Yesterday, 02:45 PM   #420
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The wheel wells are almost 40 inches when the upper control arm first hits the droop stop. So that's about 3 inches of downtravel. Starting a FL, GA and NC roadtrip tomorrow so will give things a good test then.
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