Pulsating vibration @ 65+ MPH
I'm having a really hard time with this one. Here's a short history. Please note that I have no idea whether the events and the problems are at all connected! Info: '87 Jeep Wrangler, 4.2L, 5Speed Manual, Goodyear MT/R 30s, pretty much stock.
I was out shooting with my brother, and accidentally dug my Jeep into some really soft ground. Basically just high-centered it on a pile of soft dirt. No big deal, dug it out, when home. No damage, didn't hit anything hard, etc.
Anyway, 2 days later, I noticed a pulsating/shuddering vibration at about 65MPH. It gets really, really noticable at 75 (to the point where I can't drive it past 65 because I'm scared I may bust something worse). It was not doing it before this point - was smooth all the way to 90MPH, which is as fast as I've had it.
I took it in to Goodyear - they said my tires were all unbalanced, so they rebalanced them for me. Still vibrated. Took it back, they told me *ALL* my U-joints and my motor mounts were bad. Took a look, the U-joints were PERFECTLY tight and smooth, but I replaced them anyway. The motor mounts WERE bad, completely ripped through. While I was at it, I replaed the transmission mount.
Still vibrates - nothing affected it at all. The only U-joints I *didn't* replace are the two on the front wheels (steering joints?). Can these make a pulsating vibration? Is it worth changing them? They feel fine, but I'm not all that experienced so maybe I'm not catching something.
I can feel it mostly in the floorboard/seat, rather than on any steering component (can't feel it in the shifter or the steering wheel). It feels almost exactly like my folks dodge van felt when they had a drive shaft that was too short in it. But the driveshaft is stock, and it's not dented or otherwise in bad shape. No part of the driveshaft was on the ground when I high centered it, as far as I could tell. Was basically sitting on the center skid plate/crossmember.
Any help on this would be GREATLY appreciated. I've tried to include as much information as I could, but if there's anything missing, please ask and I'll put the answer! Also, I did do a search and checked out the vibration chart, but I couldn't find anything that matched, really, other than the things I've already done (balance/u-joints/drive shaft).
Thanks in advance!