Rearend Bounce, extreme axle wrap?

Small update. I swapped the Hankook tires and the rims for old set I had, worn out Nitto trail grapplers and stock 16s. The bouncy has become better. However, it’s still bouncing in the same speed range. It’s harder to replicate and doesn’t do it as consistently as it does with the Hankooks, but it does still do it.

Also, took a measurement of camber on the rear and both appear to be close.

 

Update after a couple of months:

September/October of last year I put on a new set of Nitto mud tires after @Shortman5 was gracious enough to come over and swap wheel/tires onto my truck. Seemed to be the issue, with his set on my truck everything seemed good. However, even with the new set of tires, the problem still persist, It's not near as bad as what it was, it only shows up in a small MPH range, from some where around 40-45 and the bouncing has lessened as well. It doesn't happen under braking anymore. I have thought about swapping the new tires onto the set of OEM wheels I have, but after all the time and money to have only lessened the issue, I honestly have gotten burnt out. I've learned to live with it and avoid the MPH range in which it happens. Maybe one day I'll figure it out, I know I'll come back around to trying to solve the issue eventually.

 

Still trying to work through the bounce issue. I've noticed a few things
1) Sometimes upon acceleration it will bounce in the speed range, but its very inconsistent
2) If held in the speed range (when driving through town) 9/10 times the bounce will occur
3) The only time it will bounce on deceleration is if I am braking. If I coast to a stop in gear or in neutral, it doesn't do it. Only does it while braking.
4) The new tires now have around 15k(ish) miles on them. I've noticed that the closer I get to a balance and rotation (usually around every 5k miles) the worse the bounce becomes. Once balanced and rotated, the bounce settles back down.

The 4th point makes me think its still in the tires somewhere, or possibly in the wheels, since that is the common denominator between two sets of tires. I haven't been told that the rims are bent, but I've noticed that the lugs holes have become very worn through the years. They don't appear to be oblong or out of round, but definitely worn. The only thing that doesn't make sense in this scenario is that it will only do it under braking and acceleration. I would think if it was in the tires or rims that it would do it even when coasting to a stop.

 

No busted leafs that I know of. That's one thing that I haven't inspected closely.

Axle shafts aren't bent that I know of, but I can't remember if I checked the shafts. However, I replaced the axles shafted due to the bearing seats being messed up from a previous bearing/seal job. The bounce has been present before and after the new/used axle shafts. But, I have bad enough luck that the 'new' shafts could have their own issues.

I have not tried different shocks. The shock I currently have on (bilstien) aren't that old, and no apparent leaks. However, I tried driving it without the shocks connected, and there was no difference.

 

If you're certain you have axle wrap, install a BudBuilt Trac bar.
I went this route and all axle wrap is gone.

 

I’m not 100% certain it’s axle wrap. But so far I’ve replaced almost everything in the driveline. I’ve swapped the tcase, brand new driveshaft (not OEM, wholesale imports I think it was), different carrier bearing, new gears/bearings (ECGS), bearings, seals and new/used axle shafts in the rear end, axle and CB are shimmed to as close to perfect as I could get and new tires. So far, the biggest difference has come with new tires, but the issue still persist, just not as bad as it once was.

Only things I have not changed have been wheels, leaf springs/rear hangers, drums/shoes and transmission.

 

OP I have a second gen and I think I’m having the same issues as you. It’s like my tires turn into ovals only at 40mph. Nothing I have done has fixed it and I’ve tried many of the same things you have. More weight in the rear seems to make it worse. I read an interesting post on another forum that suggested the frame was to blame. Have you had any resolution?

 

No, not as of yet. Here lately it seems as the tires have worn more, the bounce has become more pronounced again. However, the tires don't have any irregular wear to them as far as I can see. I have no idea what else to do or what else to look at. I have still thought about swapping to a different set of leaf packs and shocks, but it hasnt been a priority. I do have a set of stock rims I am going to swap onto the current tires to see if it helps any. Best solution I've had so far, stop dumping money into it and avoid 40ish mph

 

Well poo. I’ve decided to go to the nuclear option and box and triangulate the frame all the way to the front. I’ll report back if it helps. Other than that I’m not sure what to try.

 

I would certainly be interested if that worked! Be sure to hollar back if you go that direction!

 

forgive my old eyes... I cant see if the shocks are installed upside down or not. Bilstein should be readable and not upside down. If the shocks are installed upside down the compression shim stack becomes the rebound shim stack and visa versa.

 

I thought the same thing my shocks are installed opposite of his...........

 

I just finished up boxing the frame (2nd gen) and I was unable to recreate the bounce at 40 mph. I want to drive on it more to make certain, but the benefits from boxing have already been worthwhile in other ways so far.