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Deceleration Vibration

Domer

Yup.. it's Broken...
Joined
May 26, 2020
Member Number
1489
Messages
282
Loc
Idaho
My tow rig/ wifes daily driver is a 2011 Suburban 2500. 7" lift, 325/50R22 tires, 6.0 Whipple supercharged, 6L90E Trans. It has been having a vibration on the freeway, when you let off the throttle it sounds like you are running over a rumble strip for about 2 seconds. then goes away. Doesn't happen anywhere else. I rebuilt the rear axle in October 2020 with new Yukon gears and install set. changed oil at 500 miles. Has probably 2000 miles now. Old set has went bad due to possible bad setup(but had 130k on them) rear driveshaft got new Spicer U-joints.
Last weekend I replaced the Transfer case as the old one was clattering pretty bad. Rebuilt front driveshaft in the process. Re installed everything, nothing changed. I am at a loss as to this damn sound.

thanks.


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what's the rear pinion angle like? tight u-bolts on the axle?

Did you lengthen the driveshaft when you did that much lift? I'd still be thinking that it is the driveshaft. Got a spare that you can put in to try it?
 
Pinion angles match. already checked that. The lift kit has been on the truck for about 140k miles. Truck was built when it was nearly new. I am the 3rd owner. it was not lengthened. Seemed to recently start getting worse since we got it in October.
i will check the Ubolts.
 
Its almost always driveshaft angle but it could be pinion bearings going bad too. Put it on jack stands and see if u can reproduce the vibe, pull a driveshaft if needed to eliminate a variable. Its how i found the issue in my front diff of my truck.
 
I dont think its the rear pinion. but my rebuild could be bad. It doesnt reproduce on jackstands or on the lift. i feel cause there is no road load on the drivetrain. i pulled the front shaft, but cant really pull the rear shaft as it is a slip yoke style in the transfer case.
 
How is the slip yoke engagement at the transfer case? I used to get a similar vibration in my K5 years ago, I thought it was the slip yoke getting loose. Was the replacement transfer case new, or rebuilt?

Pete
 
Pretty sure we figured it out. Rear wheel bearing had hardly any preload. You could move the hub back and forth. Going to test drive today and see if that did it.

To answer questions
Didn't think about the cup. Good idea
Rebuilt transfer case
Could stand to have more slip yoke engaged
Driveshaft only has 2 U-joints, nothing to time.
 
I dont think its the rear pinion. but my rebuild could be bad. It doesnt reproduce on jackstands or on the lift. i feel cause there is no road load on the drivetrain. i pulled the front shaft, but cant really pull the rear shaft as it is a slip yoke style in the transfer case.

had a similar experience - rumble when off throttle - on a 4runner. Turned out to be missing teeth on R&P caused by the case bolts of the tru-trac backing out. Just a minor rumble just off throttle. No other sounds.

I'd open the diff...
 
had a similar experience - rumble when off throttle - on a 4runner. Turned out to be missing teeth on R&P caused by the case bolts of the tru-trac backing out. Just a minor rumble just off throttle. No other sounds.

I'd open the diff...

I did open the diff last night, and had my gear guy come look at it. everything is good and tight. nothing broken. we did find that the rear wheel hub bearings didnt have enough pre load on them, and you could move it slightly in and out. tightened those up last night. going to refill with oil today and test drive.
 
I did open the diff last night, and had my gear guy come look at it. everything is good and tight. nothing broken. we did find that the rear wheel hub bearings didnt have enough pre load on them, and you could move it slightly in and out. tightened those up last night. going to refill with oil today and test drive.

apologies - I posted before reading the update. my bad.
 
It's easier than pulling the front shaft because there's four less bolts. Stick a cut up plastic container and a hose clamp over it.

i pulled the rear driveshaft. everything is quiet. it has new ujoints. maybe needs lengthened? weird though how it beem fine for 140k miles, and now is causing problems.
thanks
 
There is a bushing for the slip yoke in the tail shaft of the transfer case. The basic rebuilt kits that I've used didn't include it. Perhaps it wasn't replace on the reman transfer case, and is worn?

Pete
 
There is a bushing for the slip yoke in the tail shaft of the transfer case. The basic rebuilt kits that I've used didn't include it. Perhaps it wasn't replace on the reman transfer case, and is worn?

Pete

I think I'm at my max lift height. I have helper bags that I usually leave about 25-30psi in for ride quality. If I air it down, then the noise and vibration is significantly reduced. Also my driveshaft could stand to be lengthened about 2".
 
i pulled the rear driveshaft. everything is quiet. it has new ujoints. maybe needs lengthened? weird though how it beem fine for 140k miles, and now is causing problems.
thanks

The front shaft on my dd dodge 2500 started making a nasty vibe, so i swapped the cv ball and all 3 joints. Also got it rebalanced. Nothing fixed it and it was like a flip of the switch when it went bad. No clue what happened with it but a replacement fixed the issue. Weird shit happens to old stuff.
 
Go put a heavy trailer behind with a good amount of tongue weight to sag it significantly. This will reduce the driveshaft angle and push it further into the t-case.

See what happens with the vibration.
 
The front shaft on my dd dodge 2500 started making a nasty vibe, so i swapped the cv ball and all 3 joints. Also got it rebalanced. Nothing fixed it and it was like a flip of the switch when it went bad. No clue what happened with it but a replacement fixed the issue. Weird shit happens to old stuff.

I've pulled the front shaft and driven it. Definitely not it. I am going to have the rear shaft extended and rebalanced. Already replaced all the u joints in front and rear driveshaft.

Pukemaggot:
I've ran it on the lift. Sound is coming from the transfer case. Which I've found out is the rear driveshaft causing the noise and vibration.

Rockbuggy84:
It's getting a trailer out on it Saturday. See what happens.
 
I've pulled the front shaft and driven it. Definitely not it. I am going to have the rear shaft extended and rebalanced. Already replaced all the u joints in front and rear driveshaft.


i was just giving an example of a ds just shitting the bed for no good reason, even after a rebalance.
 
what's the engine/trans mounts look like?

a trans mount that fully sucks will make weird shit happen.
 
I would look at the slip yoke being worn out. Without the correct spline engagement, you probably wore out the forward 1/3 of the yoke. Lengthening your driveshaft will probably take care of the vibration, but only temporarily.

Or the wheels.:flipoff2:
 
I would look at the slip yoke being worn out. Without the correct spline engagement, you probably wore out the forward 1/3 of the yoke. Lengthening your driveshaft will probably take care of the vibration, but only temporarily.

Or the wheels.:flipoff2:

its a good possibility on the yoke. im going to take the whoke driveshaft and yoke down to the driveshaft shop and have it checked out and lengthened.
 
what's the engine/trans mounts look like?

a trans mount that fully sucks will make weird shit happen.

they look pretty good but havent really investigated it much. doesnt do anything weird when accelerating. including today with 8500lb of trailer and crawler on it.
 
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