Driveline issue...Jeep bouncing

[Lost1wing]

I'm ashamed that I don't know what kind of u-joints we have. Cv type or standard? Pinion to drive shaft angles have been know to cause problems especially with standard u- joints. Maybe just a bad joint. Wheels off is good to check axles.

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[Geometricwoodbutcher]

@chorky touched on it with this =


Let me ask too, what type of road are you driving on the experience the bounce? My truck has always done this on concrete (or expansion joint roads) from about (50-60mph). Asphalt roads are never an issue. I've been in bone stock Gladiators that do the same thing. Sometimes it's just about the road surface and a "truck thing" that you can't get away from. There's a stretch of highway here in CO where both my JTR and friend's Tacomas all "buck" until you can achieve the correct speed to make it stop.

AEV always touts their "frequency tuned" springs for a front > rear balance but I've never personally ridden a JT with these to know if they control the "bounce/bucking" any better.

I’ve experienced similar the first year I owned mine. It was similar to my 2door jk with skinny stock tires on sections of interstate during cold temps. Best description I have is feedback from the highway that you feel in steering wheel and seat. Lift, shocks and taller/wider/ heavier tires cured both vehicles of the issue for me. It was definitely during large temp drops around Great Lakes on highways with stock tires when I would feel it. As a new jeeper I found “death wobble” content, but that wasn’t it.

 

[Jaxmax]

Go back to the first couple posts, he had the Overland for a year, rode great no issues then one day in March of 2021 he had a 600 pound load in the bed, after that (not sure if right away) but still in March 2021, the bouncing started, other thing is Dealer confirmed and OP also could see the rear wheel of the truck wobbling when it was on a lift running, he has done way ,way too much, multiple sets of wheels, tires, shocks and springs, driveshaft was replaced, rear axles were replaced not the entire assembly, problem has not gone away. Has not put truck back to total stock, don't know if rear tire wobble was checked with other wheels or if dealer swapped tire around to see if problem followe tire/ wheel combo.
So what would cause a wheel to wobble, Rear axel assembly problem, frame problem, , control arm issues, 600lbs. in bed , was everything checked for Torque on suspension? , what would do that after he had it a year of no issues? I did read the whole thread, he has done way too much changing things around........Jack

 

[ZoMojave]

Lol...trust me it has definitely crossed my mind to run it off in the lake! I guess it's a good thing I moved away from the lake.

If you live in a metropolitan area, be careful not to park it in a bad neighborhood. JT's & JL's somehow have an uncanny ability to make it into shipping containers bound for India.

Not to suggest or imply anything!

 

[hickman785]

It is easy to find an issue and replace that part, never to check it again. Could they have put in a bad axle? Did they stop looking at other things when they found the bad axle?

They actually said the axle that they removed looked fine, but they replaced it anyway. They went through the entire rear end and could not find anything wrong, but they could definitely feel it bouncing.

Just an update, the other day I was sitting on a bridge with traffic passing by in the other direction. The bridge was flexing causing a light bouncing feel. That is 100% the same that I'm feeling, while driving. Usually around 40 mph and always on concrete roads. I never thought to compare it to that feeling you get on a bridge before.

 

[hickman785]

Go back to the first couple posts, he had the Overland for a year, rode great no issues then one day in March of 2021 he had a 600 pound load in the bed, after that (not sure if right away) but still in March 2021, the bouncing started, other thing is Dealer confirmed and OP also could see the rear wheel of the truck wobbling when it was on a lift running, he has done way ,way too much, multiple sets of wheels, tires, shocks and springs, driveshaft was replaced, rear axles were replaced not the entire assembly, problem has not gone away. Has not put truck back to total stock, don't know if rear tire wobble was checked with other wheels or if dealer swapped tire around to see if problem followe tire/ wheel combo.
So what would cause a wheel to wobble, Rear axel assembly problem, frame problem, , control arm issues, 600lbs. in bed , was everything checked for Torque on suspension? , what would do that after he had it a year of no issues? I did read the whole thread, he has done way too much changing things around........Jack

When the bouncing started the truck suspension was all stock, except for air bags to assist with the weight. I have always thought the entire rear axle assembly needed to be replaced, but Jeep refuses to do it. I have also never replaced the rear control arms, so I do wonder about them.

I also had the rear differential taken apart, inspected and nothing was found to be wrong.

 

[Lunentucker]

I'm ashamed that I don't know what kind of u-joints we have. Cv type or standard? Pinion to drive shaft angles have been know to cause problems especially with standard u- joints. Maybe just a bad joint. Wheels off is good to check axles.

 

[Lost1wing]

My cj5 and cj7 had standard u-joints. The Tj had a double cardan joint that failed often. I never even thought to look under the JT to see the type of joint. I just grap a handful and shake the shafts. The driveshafts that is. Thanks for the demo video.

 

[Lunentucker]

My cj5 and cj7 had standard u-joints. The Tj had a double cardan joint that failed often. I never even thought to look under the JT to see the type of joint. I just grap a handful and shake the shafts. The driveshafts that is. Thanks for the demo video.

To further clarify, the Rzeppa is on the transfer case end.

 

[InvertedLogic]

They actually said the axle that they removed looked fine, but they replaced it anyway. They went through the entire rear end and could not find anything wrong, but they could definitely feel it bouncing.

Just an update, the other day I was sitting on a bridge with traffic passing by in the other direction. The bridge was flexing causing a light bouncing feel. That is 100% the same that I'm feeling, while driving. Usually around 40 mph and always on concrete roads. I never thought to compare it to that feeling you get on a bridge before.

*Looked* fine? Or was it inspected for runout and found to measure within spec? It would be pretty easy to miss a bent shaft with just a visual check.

In a past life, here's what I'd do to try and narrow down the cause. Find the road speed at which the bounce/low frequency vibration occurs. Note the gear the transmission is in. Measure the frequency of the vibration with a an accelerometer (there might even be a phone app to do this). With the following data: Vibration frequency, road speed, tire size, gear selection, you can determine how fast each piece of the system is spinning and if the vibration correlates to any one of the spinning bits or a multiple thereof.

 

[hickman785]

They just said it looked fine. With the new axles and driveshaft installed, the jeep still bounced exactly the same. At that time, the jeep bounced at any speed over 25 mph. It was constant and got worse on concrete roads. Now that most of the weight has been removed, the bouncing starts around 35-40 mph and on concrete roads. The bouncing at 35-40 is much lighter than it was 2 years ago, but it is still there.

 

[Ianf406]

They just said it looked fine. With the new axles and driveshaft installed, the jeep still bounced exactly the same. At that time, the jeep bounced at any speed over 25 mph. It was constant and got worse on concrete roads. Now that most of the weight has been removed, the bouncing starts around 35-40 mph and on concrete roads. The bouncing at 35-40 is much lighter than it was 2 years ago, but it is still there.

Did you ever figure this out? Mine does the same thing. It is not death wobble or vibration (this is my 9th Jeep)

I'm going to check my body mount bolts today but am running out of ideas as well.

 

[Mikey_89]

Any changes for anyone with this issue? My 2020 JTR started doing the same last year (2024) around July? Only thing I recall doing was changing the rear sway bar links to Synergy adjustable.
The lift that was on the Jeep was a mess (3.5 coils with 0-1.5 inch fox shocks on the front and 0-1.5 inch Fox shocks rear and the sway bar was pulled up at a 45-50 degree angle) when I bought it in Florida. I ended up changing out to Clayton Overland 2.5 F/R, added 2 inch shock extenders, Yeti XD front adjustable track bar. Had Nitto Ridge Grapplers 37x12.5R17 on stock rims and a regrear to Dana 4.88s. Had no problems and was running some weight in the back (fiberglass ARE cap, Rhino 48x68 rack with an awning and 200# RTT plus 300# gear in back) pretty much consistently. Ended up selling a bunch of stuff due to health issues, but still have the cap on. I bought Synergy adjustable sway bar links for the rear in July and got the sway bar level. Still had the bounce. In October, swapped out the Clayton coils for EVO 2.5 plush ride coils thinking the Clayton’s didn’t have enough load on them and were too much for the ride. Still had the bounce at low speed, certain road material types made it worse, at speed 50 or above, no issues. Had tires checked, found out 3 of the 4 were cupped. Bought Fuel rims and new Toyo 35x11.50R17 AT3 tires. Still had the issue.
at some point, had a metal clanging in the back that ended up being a bad shock. Last week I put on new Fox 2.0 APS for 2-3 inch lift (removed shock extenders) and still had the bounce. Now I have a more pronounced click at low speed on the passenger side, only when braking (had this before, forgot to mention) All bolts tightened…still happens. At this point I have ordered new shocks for the front…even though I think they are fine…and will put them on this weekend, but I can’t see how this would impact the rear. I almost feel like the bounce started sometime around when I changed the rear sway bar links. Could going from a 45 + degree angle to the proper flat alignment of it cause these problems? Or possibly the rear sway bar and/or bushing be bad from the wrong angle?

 

[Rhodeskill]

My truck started doing the same thing @ about 40,000kms. Goes away at higher speeds.

 

[MattT69]

Has anyone considered or replaced the Engine and Bed body mounts? I read that they are Hydraulic and some wear out prematurely.

I feel the same baby bounce on certain surfaces especially roads that have lots of expansion joints.
Also, for those that said the frame may need support brackets, what part of the frame needs additional support? Mid section, Rear Axle forward, Rear Axle back?

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