Vibration after 65

[97' 4 Popper]

Well, I didn't want to have to do this, but after more than 1 year and still no solution, I need the opinions of the forum members. I have a vibration in my TJ that begins to be noticeable around 55, but is "liveable" up to 65. Past 65 the vibration increases dramatically and is no longer just a noise but an actual shaking feeling. After 70 it feels like the jeep is going to shake apart and you can feel the vibration even in the gas pedal and steering wheel. Now that the TJ has somehow managed to become my DD, I need to drive to NYC once this summer and to Toronto as well for a wedding and need something that can drive on the highway without being run off the road by tractor trailers going 70 plus.

This is the relevant info you need to know....

Jeep had no front driveshaft in it when I bought it, and the t case apparently had a chain that needed to be replaced. The jeep vibrates the same before and after getting a new (used) t case and front driveshaft.

I added new front shocks, front track bar, front sway bar links, new tie rod, did the alignment, changed one front lower control arm, the other front lower was changed by a PO, the upper control arm bushings look okay but I didn't check the front uppers for torque or do anything with them. I didn't touch the rear suspension.

I loaded up the tires into a truck and had them remounted and re balanced at pepboys for 65 bucks and then I rotated them on the jeep, it decreased the vibration but it's still really bad after 70. Because I'm always suspicious of shops I then bought centramatics to see if balancing was an issue. After 100 miles I ditched the centramatics and swapped out the tires between my two jeeps at the time. The wheels and tires that were on my other jeep were balanced by goodyear who charged me at 200$ for 5 tires, and of course the effing weights fell off within a year. But there were no vibes on my other jeep. Low and behold swapping out the tires and rims made zero difference literally zero.

Then I pulled the rear driveshaft and went for a drive it felt better at 70, but still it didn't solve the issue. Then after changing the u joints on the rear driveshaft and reinstalling it was back to the same vibration.

Now my thinking is the rear driveshaft needs to be re balanced or maybe there is a component in the rear that vibrates worse when power is being sent to the rear wheels. I am at a loss as to what to do. I am not a mechanic by any means. But I am damn well ready to replace any parts I have to within my ability. I am going to take it to our trusted local small town mechanic who is truly a straight shooting guy who won't fuck me. We will see what he says but I'm honestly thinking of just pulling the rear driveshaft again if I can't get the jeep straightened out before my NYC trip.

Thanks for reading the wall
- 4 popper.

 

[Gilaguy23]

I went for months trying to pin point the source of what I'll call shaking not really vibes on one of my 4x4 trucks. 2 sets of tires, 3 balances, bla,bla. I eventually put it up on jack stands on the rear and ran it up to 55. It shook so bad it almost fell off the jacks. I then removed the rear wheels,same chit. I then removed the rear brake drums and it was smooth as can be. Crappy unbalanced rear drums was the culprit. In your case do you have any lift, can you physically see any run out in the drive shaft if its up on jacks and you spin it by hand, is the DS phased correctly? Just a few things that come to mind this am.

 

[97' 4 Popper]

I went for months trying to pin point the source of what I'll call shaking not really vibes on one of my 4x4 trucks. 2 sets of tires, 3 balances, bla,bla. I eventually put it up on jack stands on the rear and ran it up to 55. It shook so bad it almost fell off the jacks. I then removed the rear wheels,same chit. I then removed the rear brake drums and it was smooth as can be. Crappy unbalanced rear drums was the culprit. In your case do you have any lift, can you physically see any run out in the drive shaft if its up on jacks and you spin it by hand, is the DS phased correctly? Just a few things that come to mind this am.

I added a 1.25 inch lift in the front, this did not effect the vibrations.

As for the rear driveshaft I have not tried to run it on jackstands to check for any run out/balancing issues. That will certainly be on the top of the list though. Removing the rear driveshaft and driving in front wheel drive didn't completely get rid of the vibration but it made it more liveable at 70.

As for the rear drums, I am shocked that was the cause of your issue. I'm at 100k miles and the shoes and drums look to be original and in good shape. I initially had a lot of slop in them I just adjusted the stars on them and they ran great. Then later I had a brake cylinder leak on my rear driver drum so I had to replace the cylinder and the hardware on it. Now the braking is excellent same as discs but it makes noise the first 5 or 6 times stopping in a day if I really press hard. I am going to check the star adjuster again because for whatever reason it didn't want to thread outward more than a few clicks from the all the way shortest length. That is compared to my other side which has atleast 3 or 4 threads showing. Maybe I will take apart the passenger side drum as well. Let me know what you think, overall no effect on the vibes as far as I can tell.

I have come to realize that I have a clunk in my rear suspension when going over a bump at low speeds. The only thing I could think if is when I dropped the gas tank maybe the nuts backed off but I highly highly doubt that. I will certainty take a look. My rear lower control arm bushings are also completely rotted out, I have two new factory lcas ready to go but I never swapped them out. My thinking was it wouldn't matter, since changing out my front driver side lower control arm seemed to make no difference and the bushing on that one was destroyed. Maybe I need to replace more than just the one to feel a difference. Maybe even uppers idk. I am starting to think that it is a driveline vibration, since rotted out bushing on my track bar also didn't effect anything, having a shock with the top nut so loose it was gonna fall off also didn't effect anything, tie rod out of alignment also no effect, after these experiences just makes me question whether I even need a working suspension to roll down the road.

Lastly, I have spent a lot of time removing rust with heavy duty needlescalers and the like, there are no damaged or bent mounts or support points that could cause this vibration. I final thing to note is I replaced my rear pinion seal and it didn't effect the vibration but since it is along the driveline I thought I would mention it. At this point I'm just giving as much info as I can. Man this thing feels pretty good up to 65, and tracks damn well straight. But after 67, 68 mph the vibes gets very bad very fast. I have a lot of work to do.