Rearend Bounce, extreme axle wrap?

I've been dealing with a bounce from the rear for a while now. It will do it at about 40ish, mainly when holding steady at that speed range. It will also do it when slowing down, more prominent under a hard stop. It does it to the point that I can see the bed bouncing in my mirrors.

For the longest I assumed it was the tires, or warped rotors. Rotors, pads and calipers are brand new. Tires have been double checked for balance, any kind of out of round and bent rims. Tires are in balance, nothing is apparently wrong. Also, I have installed hub centre rings with conical extended thread lugs.

Also new is rear wheel bearings, axle seals, new (used) axle shafts, new 3rd with fresh bearings and gears (ECGS), and new (after market) driveshaft. Bounce has been present with all of the old parts, including old OEM drive shaft. Shocks are Bilstien and have around 10K'sh miles. They appear to be working in order. I removed them, checked for leaks, and will take just about my full body weight to get them to start to compress.

I disassembled the shackles and front hangers to regrease everything, and installed new bushings on the upper shackle mounts to see if that would help. So far, no difference. However, I did notice that both leaf packs are both really torqued to the drivers side, especially the driver side, I'm not sure if that makes a difference or not. I also noticed that it looked like the driver's side lower shackle bolt looks to be slightly bent upward. Upon re-installation, it seemed that is was indeed bent upward just slightly. Both shackles are OEM.

It is also worth mentioning that I've had a driveline vibration that I've been chasing but have yet to figure out. I've measured angles, swapped shims, and have made it better, but it is still not perfect. Pinion angles looks to be about 2 degrees down.

I've removed the shocks to see if it made any difference, and it made no apparent difference. Right now, I'm running a used set of the discontinued Wheeler's 8 pack. I previously ran a bastard pack I made with the OEM main leaf and cut chevy springs. With the bastard set, I don't recall having the bounce nor the driveline vibration. It's been close to a year and a half since I've been running the Wheeler's pack and as best as I can recall, I've been experiencing the bounce ever since I installed the Wheeler's springs. I've also noticed at times if I'm rolling down the road, and abruptly let off the gas or tap the brakes to disengage the cruise control I feel a very hard clunk. I wish I still had the old pack to reference, but I tossed them about a year ago. Perhaps I'm getting extreme axle wrap?

I'm at a loss, don't know what else to even look at. I feel like trying to swap in a new set of springs would be a waist of time. I've attached pictures of the springs, shackle hanger, and the angles I'm getting on my pinion. I love this truck, but I'm ready to park it and start over on something else.

 

When I did a complete brake swap on my truck (96 STD Cab 3RZ 5 Spd) truck had a shimmy and when braking it would really shake. Took the rear drums off and had them "Trued". Once this was done I took the truck in for an alignment and asked the shop if they could measure the rear wheel camber(s) everything seemed good and the shimmy shake was gone. I am running OME suspension that was designed for STD Cab 1st gens.

As for driveline this is a good read:
https://www.tacomaworld.com/threads...-acceleration-with-updated-driveshaft.493029/

 

I've thought about the rear brakes being slightly warped or out of round, but with it bouncing even when not braking, I talked myself out of it being related to the rear brakes.

 

Yeah, only other thing I can think of would be to head into an alignment shop or the ones that straighten out frames (alignment rack) to check and see if all of the tires are "True". So hard to tell plus forking out the cash to check and see of everything on the back end is good to go, and if so you still have to either find the problem elsewhere or re-invest in components you have already tried to improve upon. It is frustrating....

 

Theoretically, if I set the brake shoes to not be in any kind of contact with the drums, wouldn’t that rule out the bounce being anything related to the rear brakes? Or at least rule it out as a cause for the bounce while accelerating or holding that the specified speed range?

 

Very true, you can completely loosen them up so they are at 0% contact with the drums and see what happens. Just that when I put on the new drums thats when my problem started on the vehicle. Once they were spun by a shop everything seem to be back to normal. Only other time I had ever dealt with "vibration" was when I put new spicer U-joints on my Ford F250 with zerk fitting, anytime the vehicle went above 55 it vibrated like all hell. Did not realize the little zerks underneath could cause so much disruption for being as small as they were. had to pull the driveline off and get it rebalanced by a speed shop.

 

axle wrap is more of a "clunk" when letting off the brake at a stop. the "bounce" you describe wouldn't be axle wrap especially while moving. so i think you can rule that out?

bounce is usually suspension related. isn't there supposed to be a boot on that shock lower in your first pic? could they be valved "too stiff" and you are getting every nook and divot in the road?

if you can "safely" take a video I would start there and see what the smarter TW people think

 

Your pinion angle is 2 degrees DOWN? I'm no expert on drivelines, but seems like if anything, it should be pointed up, towards the trans...

I'm with @frizzman, that this isn't axle wrap.

Your springs definitely tweaked, which is kinda weird. Never seen that before.

Seems like you've gone through everything BUT the springs, and seeing as how they were used to begin with, that's where I'd start next.

You should be able to take them to any spring shop and get them re-arched, which should also take care of the tweak towards the driver's side. Or, finally treat yourself you a NEW set of springs (and shackles).

Also ensure your pinion angle is correct; pointed down doesn't sound right.

 

I'm not sure if there is supposed to be a boot or not...the shocks are about 1 year old and IIRC I don't think they came with any. I could be remembering wrong. I do however remember debating if I wanted to use boots on them or not because I remember reading debate on that subject...mainly about mud/water getting caught in the boots and corroding the shafts and such.

The shocks being valved too stiff was a theory I had. I do feel every nook and divot in the road but I attribute that to getting too used to my full sized truck I removed the shocks and drove without them, but I still could feel a bounce, so that would lead me to believe that its not the shocks? Also, the shocks are the Bilstein 5100, which are pretty standard and I contacted Wheeler's about them before I purchased them since I'm running their springs. They didn't have anything contrary to say about that combo, which I would hope they would if it was a bad idea.

From everything I have read, understand and have researched, with a double cardan or CV shaft like our 1st gens have, the pinion needs to be as pointed so that it is as close to inline with the rear most portion of the driveshaft as possible to avoid driveline vibrations. Most places I looked recommended a slight 1-2 degree down to account for axle wrap, so that under load the pinion would wrap up and be in line with the driveshaft. if I'm wrong in that or my understanding, I certainly don't mind being told so and would welcome it at this point! I settled on this set up because it gave me the least amount of vibration..not zero vibration, but enough that I could live with. I went through every shim from 2-4 degree with a variation of a carrier bearing drop on all of them and this was the best that it seemed to get

What is odd is that both springs were twisting to the driver side. Which I don't understand. They were both still attached to the axle, but I would think that wouldn't cause them to twist in that way. The passenger side was not as bad as the drivers. I'm hesitant to pull the trigger on new springs without 100% confidence with all the parts I've already thrown at it..but on the other hand I just want it right and I'm already into it this far..

 

I think people had issues running the boot on top. running the boot on the bottom there is a tiny pin hole on the one side to let the water drain out. honestly the shocks should prevent the bounce, if you took them out of the picture I'm not sure they were all that great?

from my understanding whatever you "lift" should be the degree of shim you use. so 2" lift would be a 2 degree shim to point the 3rd member up towards the driveshaft to reduce vibrations while driving. if you pointed the pinion down then you are creating greater angles for the driveshaft to work at. like always turning the steering wheel and the CVs are engaged, it will wear out sooner and possibly cause issues. they can handle a lot but if you run it "always" like that it could be worse. the more straight shot the driveshaft can be at the better.

 

True, they should prevent a bounce. But as difficult as they were to compress, it doesn’t seem like a likely culprit, but I still haven’t ruled them out as a possibility. I’m note sure how else to test if it’s shock related.

I think we’re misunderstanding when I stated the pinion is 2 degrees down. I have 3 degree shims installed, correctly, with the fat part to the rear of the truck thus pointing the pinion UP, pointing the pinion towards the drive shaft. BUT, the difference from the angle of the drive shaft and the pinion flange is 2 degrees down, which should help to account for axle wrap so that under load the pinion rotates up slightly and will be inline with the DS. The 2 degrees down is the working angle of that u-joint, if I understand correctly. And since a u-joint does not need to operate at 0 degrees, that should be fairly close. It’s as close to perfect as I’ve been able to get. Maybe that makes more sense

 

If you took the shocks off and there was no change, then your Bilsteins are just like new, they are terrible, I don't think I will ever buy them again.
I recommend you get some real shocks on it

 

But would shocks only cause a bounce at a certain speed? Other than that specific speed range, there’s no excessive bounce when hitting bumps

 

Possibly, the 5100s on front of my 05 Sequoia seem to do the same, the smallest bumps in the road are throwing the tires and shocks are so limp wristed, they can't control anything.
But then on super smooth road, the truck is smooth, it isn't our tires.

Another thing, have you done the rear driveshaft U-joints? Even if they look fine, replace them with quality joints, then you know they are 100%.

 

Drive shaft is brand new with Spicer joints, that have been properly greased. The OEM shaft was replaced under suspect of having issues. The new DS solved some of the issues I was having before, but the bouncing persist.

 

That just doesn't make sense to me. Even with the double joints, I would think you want the shaft to be as straight as possible. Ideally you'd have a perfectly straight line between the trans and the pinion (trans and pinion both at same angle). That's usually not possible, but you still want to minimize the angles.

I've never heard of angled shims doing anything for axle wrap, that's a new one to me. There's a mod to clamp the leafs together right in front of the axle, and that helps axle wrap.
It's not "perfect" but it helps. The farther away from the axle, the more it reduces axle wrap, but it also makes the ride stiffer because it's limiting movement of the leafs. I've had this for like a decade...

I would bet that whatever vibe issue you are(were) having is also related to the issue you're having with the bounce.

I understand the hesitation, but it looks like you've replaced everything else with the shotgun approach. Why stop now? lol Getting them re-arched is typically a lot cheaper than new springs, so that may be a good first step. Or, just buy once, cry once. A set of OME Dakars are like $350.

Before diving too deeply, though, ensure that all your leaf/shackle mounts are straight. I can maybe see that being why the leafs are bent. Can you recall if they were bent like that when you got them?

As I said, the angle of your leafs is definitely weird, and I could see that angle causing the springs to bind up.

As someone else said, if at all possible a video would help. Well, it MIGHT help. Sometimes videos never translate very well, and what's VERY obvious to you might not get picked up on the camera...

 

It may not make sense, but any shim above or below the 3 degree that I have installed made the driveline vibration I had worse. Again, i still have what feels like a slight drivline vibration, but it's not as bad as it was. The angle shims were not installed for axle wrap, they were installed because I was/am getting what is apparently a driveline vibration. I just included that bit of information just to make everything known, not to try and solve the bounce issue.

It didnt start as a shotgun approach believe it or not, but that's a story for another time all the parts that have been replaced were done so for one reason or another, but none were done due to the bouncing..although with each thing replaced I thought that SURELY it would solve the secondary bouncing problem.

I will double check the mounts themselves, I don't recall having any issues when initially mounting the leafs. I know I mounted them without them attached to the axle, but even with them attached to the axle as in the pictures, I wouldn't think it would cause the leafs the torque one way or another.

I figured out a way to mount my knock off go pro, I'll try and get a video to see if anything sticks out.

 

The pinion should point 1-3* below the double cardan joint in a leaf spring application to account for spring wrap just like @kuntry09 said. With traditional single u-joints, the pinion should be 1-3* below parallel with the output to also account for spring wrap. Links can be set pretty close to dead on.

Here’s some reading...geared more towards high hp guys drag racing but the same principles apply to our trucks too

https://www.quickperformance.com/Pinion-Angle-Measurement_ep_45.html

 

I was able to get some video while driving. Sorry it's upside down...if someone can tell me how I can invert the video and upload it again, I will. It's really long, but I'll hit the highlights of where to skip to. There's an annoying rattle that I guess is the camera in the case, don't turn it up too loud when starting out lol

From 1:00 to the 3:00 mark I'm holding steady at the speed range that I'm getting the bounce. This road has been freshly paved so there's no big bumps or holes and is pretty flat. You can see the axle moving, but it's not extreme, and it's not as much as what it felt like in the cab. Perhaps someone can see something I can't.

At about the 3:15 to 4:45 I'm cruising about 60ish and I'm letting off the gas...I do it multiple times to try and get a good video. You can see the pinion drop abruptly, and the leafs torquing. I'm not an expert, and I know that on the first gens axles wrap is bound to happen with any set of leafs, but this seems pretty extreme to me for a leaf pack that I was told didn't have that many miles. The best example of it is from about 4:15-4:30.

https://www.youtube.com/watch?v=zRxhFrIECps

I tried to see if the hangers themselves might be tweaked in some way, but because of the way they are made, I see no good way of trying to measure and see if they are square. I'm open to suggestions on how I could check and see if they might be tweaked, visually they do not appear to be.

 

Yes, this is how I have always envisioned the drive shaft angles. That's not how I understood the OP to be describing his pinion angles. OP said is pinion os 2* down to account for axle wrap. That's what I was referring to.