2nd Gen Non-Engine/Transmission 37.5mph rear end bouncing . . .

[TXRam]

Hey guys,



A long time ago, I remembering some posts about the rear end of some people's trucks bouncing when the speedo was at or around 37. 5mph. Mine has always done this, but recently I changed the shocks (new Rancho 9 position shocks), and now the bounce is much more severe (because the shocks are stiffer and not absorbing all of the bouncing). The truck is a 99 LB QC 4X4.





Has anyone had this problem and found a fix? I am thinking it must be an out of balance drive shaft or a problem with the mid axle support (whatever the technical name for it is???).



TIA!

 

[BV]

My 99 had a slight vibration at that speed and it went away when I rotated the tires then came back after I rotated again. I figured it was a bent wheel, tire out of balance or one that was out of round. It didn't vibrate with a load or with the original rear tires on the front end.

 

[TXRam]

Thanks BV.



Mine has had this problem since I bought it. Now I have different wheels (aluminum), 3 different sets of tires, balance and rotation doesn't help, etc. Like I said, the new shocks just made it feel bad enough that I need to fix it. Maybe a u-joint???

 

[CATCRACKER]

have the same problem on 99 cannot find a fix that is a main reason i am buying an 03 and not putting my truck in the tdr clasifieds. it is not a bent wheel or alighnment. it pisses me off though. for only 32000 i solved my problem i suggest you do the same

 

[Dheadington]

rear end vibration

I also have same problem on my 99 have had it since new had to dealer aeveral times nobody been able to correct.

 

[TXRam]

Catcracker,



What things have you done to try and correct it? I'd like to know so I will put those at a lower priority on my list to check-out.



Thanks!

 

[TradedV-10foraCummins]

I've got the same problem, and it has been there since new. Mine is also a 99. I find it strange that most all who have posted here have 99 modles?! Mine is a QC, LB, 4wd. I've changed the wheels, tires, shocks, and brake pads and shoes. The problem seems to lessen with a fresh tire balance, but isn't eliminated. I can't find anything loose or worn in the drivetrain.

 

[Dheadington]

37.5 mph vibration

I have Kelderman air ride suspension on truck if I lower rear of truck just alittle vibration gets better I believe drive shaft angle is off enough that is causing problem. I may try to shim shaft angle and see if that corrects problem.

 

[Missouri Mule]

I had the problem changed out tires and wheels took care of problem. Either the one wheel was bent(out of round) or tire(s) were bad (second set).

Did find belt popping/rolling/shifting (what ever you want to call it)on rear driver's side but the passenger side tire/wheel really made the truck shake. Jacked backend off ground truck put it in high gear and ran it at different speeds. Between 40 and 45 was the worse.



Driveshafts I have read will vibrate all the time if out of balanced, but my ford van thru a weight and it seems to me it only caused vibration at certains speeds (got it fixed).



Center carrier bearing will cause problems now and then.

 

[LSchick]

I also posted this problem a while back. Have spent a LOT of money trying to find it. Dealer says its there but is minor, Sure is a minor problem if you don't have to drive it or live with it Mine was fine until i had a new pinion seal and yoke installed and then 6 brand new tires at the same time. In the last year have replaced all tires again all balanced on a road force machine. again, again again etc. and another new yoke replaced. Wheels are Perfect. Tried balancing the drive shaft with hose clamps as the manual suggests ,nothing has helped. Have some other ideas to try and locate the problem and will see what develops when time permits.

 

[sag2]

If you want to find out for sure what component is causing the problem, have your service manager contact his factory technical advisor. They all got this new vibration analyzer a while back, and the demo I saw was very cool. It shows what is causing it, and suggests possible causes. It takes all the guess work out of it. The old style was called EVA (it was a GM essential tool) and the new one is the MTS 4100.

Maybe they would be willing to bring one to a local TDR get together and demo it. Costs nothing to ask.

 

[Harry V]

Just wanted to add that my 99 does the same thing. It is a fairly recent development though. Also most noticeable at 40 mph. However I can feel it at low speeds too. Pretty sure it is a tire or wheel issue due to the frequency. I jacked the truck and ran it. I found one of the rear tires to have a slight flat spot. My next move was going to be tire rotation and see what happened. I have about 20K on Dunlop Radial Rover RV 255 R85's.

 

[fest3er]

Put the rear axles on jack stands so the tires are off the ground.

Put the trans in neutral.

Spin the tires by hand. Look for the tread 'moving' up and down relative to a fixed point (like the ground or the body). Also, see if you can see the edge of the wheel 'moving' up and down as it rotates.

If you see tread moving up and down relative to a fixed point, the tire/wheel combo is out of round. Try having a tire shop spin the wheel 180 degrees in the tire and re-seating the beads.

A perfect combo has the tread spinning perfectly and the wheel spinning perfectly. An adequate combo has the tread spinning nearly perfectly with the wheel 'moving' up and down a bit.

A bad combo has the wheel and tire 'moving' up and down out of sync.

A bent wheel won't necessarily cause bounce, unless the impact also threw the wheel out of round.

My truck bounced like that since it was new, until I switched to 19. 5" wheels. After taking the OEM tires/wheels off, we did a quick check and found that one of the combos was 180 degrees off (that is, the high spots were matched up instead of one high spot with the mate's low spot).

The factory *can* mount the tires wrong. But there're few reasons you can't perform a simple 'visual' check at home. And there's no reason for a tire shop or dealer not to perform such a visual check

Fest3er

 

[Jetson]

This sounds like it's mainly 99's and mainly 4x4's . I think the higher lift must be causing the angle of the dangle to be off as Dheadington said. My truck has not done this (4x2). I did notice something strange recently. For various reasons, I have not rotated the new Michelins I put on the rear, and they are worn on the inside.

 

[243]

Clint,



I believe I remember this happening on my 99. Was it a very fast bounce?

 

[Missouri Mule]

I took my Freightliner to balance the tires thinking the computer balance would tell if a tire or wheel was flat/out of round.

The the guy told me one of the tires needed a lot of weight's on one side. Truck still shook front and rear at different speeds.



Finally had a roaving tireman check them out he found that my left front tire had one large flat spot. (the one that had all the weights on it)



Changed out both front tires no more shake, rattle and roll.

It almost drives as smooth as the Mule

 

[CumminsPower98]

Well I'm going to break the string of '99's here and talk about my '98. I have had this 40-45 mpg bounce/hop since I got the truck used. I have had different tires and wheels on the back and rotated them all around also. The hop is always there no matter what I do and doesn't seem to change much. My rear driveline had a bend in it so I had that rebuilt thinking it would fix the problem but it didn't help at all. To me it feels like tires and wheels because it's a pretty slow and heavy feeling hop. I have watched my tires turn while on jack stands relative to the concrete before but need to do it again I guess. I also need to get the tires balanced again and see if that helps. It's interesting to see others are having the same problem. I thought I was alone on this one.



P. S. 33x12. 5x16. 5 BFG A/Ts on aluminum 9. 75x16. 5 American Racing wheels. I know this sort of setup is harder to balance.