More AWD 1500 lift info
This seems to be the Portal AWD 1/2 ton Lift thread so I am posting my info accordingly................
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So it's time to get some ground clearance under the Van before camping season starts again. After living with the AWD 1500 Passenger van for a while now I have some observations and thoughts about the suspension. When the Van was new and empty the rear bump stops had a couple of inches of clearance and the van did rock side to side on certain road conditions, noticeable but not a big deal (the Van has no rear sway bar). The Van now has a heavier constant weight with a basic interior, that puts the big progressive bump stops at about a 1/2” clearance. The Van handles better now even though it's heavier, due to the rear bump stops acting as a sway bar and eliminating body roll. The thing handles the twisty two lanes way better than most would expect, even at GVW. Which is why I am going to try not to screw up the excellent road manners the Van has stock when I lift it. I feel like GM relied too much on the rear bump stops for spring rate and when lifted off them, more spring will be needed or at least a sway bar and very good shocks.
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The rear springs are way too soft 2240lb capacity, riding the bump stops (is no way to go thru life) even if handles good, it rides great on small bumps not so good on big ones. I found some 2900lb 92-99 3/4 ton suburban springs #22-907 that I may try,
http://www.dallasspring.com/publications/GMLD.pdf A 3/4 ton van spring jumps way up to a 3700lb capacity and has much less arch, the suburban spring is almost identical in specs and gives about a 1” lift just due to the spring pack thickness, the 2900lb springs may not offer much lift at fully loaded weight but should offer better weight control. I will then use lift blocks to set rear height. I am told a 2007-2013 GM 4x4 1500 Pickup stock rear 1 1/8” lift block will fit our vans, they have the nice anti-rotation tangs cast in and cost around $20, A 1 7/8” 1999-2006 and up block may be too much for now. I am guessing after the Van has some rear bump stop clearance again, a rear sway bar will be needed to match the good handling I have become used to. I do like air bags and have many sets in use now but the Van has had an increase in constant weight so I want to spring for that and maybe use air bags later for fine tuning.
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The passenger van has much better shocks than the cargo van, I suspect the Van Conversion companies made GM tune them to a higher level than they are normally willing to achieve, it's too bad they are too short. I talked to Bilstein about rear shocks and found out that Van shocks are valved very stiff to deal with all that mass swaying around and prevent porpoising on Hwy expansion joints. I also found out a 4600 series 3/4- 1 ton van shock #24-025706 is 23.23” extended 14.80” collapsed and valved at 389-73 vs. #24-024815 1/2 ton van replacement rear shock that is 20.89 Ext and 13.29 collapsed valved at 361-68. So a 3/4-1 ton van replacement shock is valved close and is a 2.34” longer shock for a stock 1/2 ton AWD Van. The 5100 series rear shock #24-185615 looks good it is 26.2 ext and 16.81collapsed but valved at 287-77, which Bilstein says will not be effective on a heavy van and could be to long for my lift at 3.5” longer collapsed and could require extending the bump stop down to prevent shock damage (back to first base). 92-99 GM pickup, Suburban and Tahoe shocks will bolt on, unlike the 99-06 Pickup rear shock everybody tried to put on these AWD 1/2 ton vans and the 92-99 shocks are longer, with a 2dr 4WD Tahoe shock being slightly longer yet at about 25” ext. ALL OF THESE SHOCKS ARE VALVED VERY LIGHT FOR A VAN 150-230 vs 389 and 50-60 vs 60-73 Bilstein will not recommend any shock for a non stock application and said minor valving changes do make a difference, they did say they will re-valve their 4600 and 5100 shock if you sent it to them, I got the impression you have to provide valving numbers?
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Bilstein does not make a front replacement shock for our AWD 1500 Van so stock lengths and valving were not available to compare, we all know 4600 HD series # 24-065009 a 99'-06' GM Pickup, Suburban, Tahoe front shock will bolt on and is the exact length needed for a stock height van, 15.43 Ext. and 10.09 collapsed, valving is 292-119 is the valving correct for a van? Bilstein would not comment, the front weight balance of the Van is certainly much different than a pickup, I am at GVW front and 200lb under rear when loaded for a week in the bush. The 5100 series #24-186643 front lift shock 99-06 PU etc.. is 16.3” ext and 12.54” collapsed, which could be too tall collapsed for some people without enough lift, the valving change is huge at 366-240 vs 292-119, the ride has to be affected which I think Brian observed when he said he did not like Bilsteins ride. My plan is to crank what I can into the front, 1” or so and see if the front shocks top out and the ride is terrible, if so then shock extensions or 99-06 1/2 ton front lift keys and longer 5100 series # 24-186643 front shocks will be used. I have never lifted a rack and pinion steering front end and love the steering feel it provides stock. I am not 100% sold on 3” front lift keys not having any bumpsteer and weak GM ball joint wear issues, been there done both over and over. I was told by Bilstein 4600 HD and 5100 is the same shock except body material and 5100 is usually much softer than a 4600 HD. I am a big fan of Bilstein and have good reason, I have used most of the usual brand shocks and have had minor success with them all and have had excellent performance that lasted 100,000 miles or more from every Bilstein, I do prefer a tight controlled ride and they usually deliver that on all surfaces.
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I almost ordered 3/4 ton Suburban rear shocks thinking close enough, suburbans are big and heavy and they bolt up, Wrong. This is what motivated me to ramble on so very long.............
Bilstein wants you to use the 5125 series for custom applications, they will not have proper top mounting type for our vans. Custom shock adapters work but are not the best choice. The best choice may be to find the right length 92-99 Pickup/ Suburban shock for your lift and have the valving changed by Bilstein. They talk in a type of code “like that shock won't work but I can't legally tell you what other shock will” you have to keep hitting them with part numbers and they will give the spec only, not a blessing. I waded into this mess and thought I might save some people from starting from scratch, I may not have 100% accuracy but gave it my best shot so add your data accordingly.
