1991 Suburban springs, questions

[1976gmc20]

Our half ton 4wd Suburban has some suspension issues. It just sort of wallows down the road with perceptible body roll not really correlated to cornering, like it's not really sure which way it wants to lean. It doesn't wander but it just feels squishy and unsettling. It didn't used to be this way, and the several other solid axle 4wd Chevys that I've owned were always solid handling.

It has new shocks, new tires ( LT235/75R15(C) @ 45psi ), and I took up a little bit on the power steering box adjuster a while back to take up a little slack. It goes where you point it, but it feels more like a boat than a truck.

I'm thinking the rear springs are wore out and in fact it has a static lean to the left rear. Does that make sense or could there be something else causing this issue?

Does anyone know if 73-87 3/4 4wd pickup rear springs will just bolt in ???

[centexan]

I'm curious about this as well as I am having similar issues with my '89

[Ski-me]

Finding used springs in that era are more than likely going to be on their last legs too....a lot of springy feeling. I'd go to a local spring shop and get some new ones ordered up. That helped my blazer a lot! Just standard, stock ones will probably give the truck some new life.

Also, take a look at your spring bushings. Both front and rear. I'm sure the rubber is probably worn out by now so you may have to replace with new, poly ones. That will help tighten things up a bit.

These will help but it may not be everything. You could also have some worn rivets on the spring perches, or frame connections. Ball joints, and tie-rod links could also be contributing. Springs could help a decent amount though.

I also added a little more height in my 91' suburban because the tend to squat a little in the rear (even more so with worn springs). I used a 1" zero rate lift block to help out.

[1976gmc20]

Okay, thanks

I was thinking salvage 3/4 ton springs would be a lot better than my worn out 1/2 springs, which were barely (or not!) adequate to begin with. But it might be better to just take it to a shop in Billings and have them look at it and give me an estimate. I just don't want to put too much $$$ into what is now essentially a backup vehicle. But it would be nice to be able to take it out on a long road trip if I wanted, without "swimming" the whole way.

A couple years ago somebody suggested just finding a set of 3/4 ton axles and springs and basically converting it to 3/4 ton. But I could see where a simple project could get expensive in a hurry: the driveline yokes would certainly not match and then who knows what issues I would run into with the brake lines ??? If I had a complete 3/4 ton 4wd donor truck then I would probably be fixing that up instead!

[Ski-me]

I was just in Billings yesterday for a graduation...

Anyways, if you can get cheap 3/4 springs, I suppose you can try them out. Just don't know what kind of salvage yards you have up there. If you found a 3/4 suburban 88-91, it is possible to swap that into your truck pretty easily. I did this on my 89' K5. Rear end was a 14 SF, and the brakes hooked right up. You will need to go to 8 lug wheels though....or it's possible to keep the 6 lug with some modifications (what I did).

But, the more you try swapping the more you get into the "might as well" think...costing more money.

[1976gmc20]

Originally Posted by Ski-me

I was just in Billings yesterday for a graduation...

Anyways, if you can get cheap 3/4 springs, I suppose you can try them out. Just don't know what kind of salvage yards you have up there. If you found a 3/4 suburban 88-91, it is possible to swap that into your truck pretty easily. I did this on my 89' K5. Rear end was a 14 SF, and the brakes hooked right up. You will need to go to 8 lug wheels though....or it's possible to keep the 6 lug with some modifications (what I did).

But, the more you try swapping the more you get into the "might as well" think...costing more money.

I was just thinking about swapping the rear springs only, not the axle too.

If I swap the rear axle, would have to swap the front axle also to keep the wheels and axle ratio the same, but then again: drivelines, brake lines, etc etc etc

I would love to go to eight lug 16" wheels, and 16" 10pr tires like the two pickups. I tried to find junkyard six lug 16" wheels a couple years ago, to no avail. BTW, the six lug 16" wheels from the GMT400 series will not fit, even if you cut out the center holes. The back space is different and the wheels hit the steering knuckles I finally got some used 15" steel rally wheels to replace the alloys of which one was cracked.

My mom still lives in Colorado Springs. I graduated from Wasson in 1972

[Ski-me]

I think I've seen 8 lug, 16" wheels from my 2004 3/4 ton Yukon on some of the 91' era suburbans. Looks pretty decent but you do have to worry a little about backspacing.

The front 1/2 and 3/4 axles are the same (I think 87-91)....just the outside spindles and brakes are different. I swapped my 6 lug stuff over to the 8 lug front axle. That way I could keep the 6 lug. Axle shafts were the same and just slipped right in. IN the later years, I think the spline count went from 27 to 30, that's why I'm saying the newer ones.

Axle ratio is a big thing. I was doing that in the same process so found a 3/4 suburban as a donor with 4.10 gears. Swapped them in.

Rear axle is a little more tricky to keep the 6 lug. Have to find axle shafts, backing plates and drums from the newer 14SF axle with 6 lugs, pull those, put in a 1/2 thick spacer between backing plates and you are good. Just a little more involved. Our junkyards are pick and pull so I was able to piece together what I needed in the junkyard and then buy as one unit. For $100 an axle, I had a custom one out of the box. Just had to get the spacer fabricated.

That way the spring perches and shocks all line up.

You could then find a conversion u-joint but it will depend on how much axle slip you'll have still available. 14 bolt pinion is a little longer than 10 bolt so will push the slip further into t-case.

[1976gmc20]

It wouldn't be worth all that to me if I couldn't swap in the heavy duty full floating 3/4 (or 1 ton) axles. I wish that I had the axles from under my old 1973 K-20 under this rig!

I'm sure brand new custom made springs installed by the shop would be cheaper than all that messing around. Otherwise I might as well do it right and put Rockwells under the old Burb

I dunno about the 2004 wheels, but the 1988-1998 6-hole 16" pickup wheels are backspaced way out almost to the outside of the rim*, so they hit the tie rod knuckles before you ever even get close to the hub - not sure they even start onto the lug nuts. I haven't heard good things about spacers, either

* I used one of those junkyard wheels turned with the inside up as a "bucket" for the tire chains in the back of my GMC C-20.