Speed based noise

Ok well I've gotten to the point where I just want to rip my hair out. I have a rotational based noise coming from under the jeep. So far I've replaced every u joint, front hubs, rear axle wheel bearings, both front and rear axles have been rebuilt and regeared, and I just tossed in a new front driveshaft to replace my old one with a bad slip joint. I have no more ideas on where to go here, above 65 its a fast vibration and at slow speeds it feels like a spinning clunking noise. I'm tired of spending money on fixing this noise. The regear was because I thought the noise was my pinion bearing in the front axle which was bad. I thought that was where the noise is coming from but its not, so I replaced the driveshaft with the bad slip joint... still has the noise. Like I said all u joints have been replaced within the past few months in the driveshafts and axle shafts and the front hub bearings were replaced a few weeks ago. The rear axle wheel bearings were replaced during the regear which was done about 2 months ago. The noise goes faster or slower based on my speed, I've looked everywhere and really can't see anything or feel anything obvious. The only way I can describe it would be a spinning clunking or thumping noise that happens pretty quickly, at a high speed the clunking is happening so fast that its just a big vibration that almost pulses on and off and is almost unbearable to drive past 65. Please give me some ideas guys :smsoap:

Btw my setup- 99 xj automatic np231 with hack n tap and xj front shaft, 4-5 inch mix and match lift, dana 30 with yukon 4.88s and an aussie locker, chrysler 8.25 yukon 4.88s w/ teraflex disk brakes, running 33x12.50 km2s on 15x8s

sounds to me like either rear u-joint angles or possibly even bad motor mounts cuasing driveshaft angles to be off under load.

I have 4 degree shims under my rear leafs and the pinion angle is perfect. The noise can even happen idling in gear on the street, I will check my fan up front to see if the motor is moving and rubbing it. I find it hard to believe tho because it would happen during idle in park, I feel the clunking under my feet or so it seems.

The thumping is loud enough to hear from outside the jeep, this isnt just a faint clicking like a worn out u joint. I checked to see if anything is rubbing on the driveshafts and theres nothing touching them.

Have you checked the t-case?

When I bought my first XJ which was a '97 the dealer thought there was a bad rod bearing. While pulling the engine I found that the torque converter/flexplate bolts were loose. Pretty easy check. You might want to try it.

well it cant be driveshaft or motor mounts like i said before if it does it at idle! so, to get this right, it is a rotational noise that goes faster the faster you go speed wise(not rpm wise). it does it at idle in park. it feels like its coming from the floor of the jeep. my guess would be that there is something wrong with the transmission. since rpm induced would be more engine/flexplate related. i dont have the internal breakdown of an aw4 in front of me, but internals are spinning in park and would go faster as speed increases. nothing is spinning in the transfer case in park or stopped. just my thoughts for now.

Sorry I meant idling in gear as in moving without giving it gas. I think its the centering ball in the rear driveshaft, I'm gonna remove it and see if the noise continues. I did mess up some of the needle bearings during a u joint install and believe I mangled up that little spring inside the center ball. I didn't think much off it when replacing the joint and just put the bearings back together, the spring should of been replaced but it was super late and I was getting delusional.... stupid me. I have a spare driveshaft that I will take the centering ball out of and toss it in my rear xj shaft that has all new u joints in it.

Casey-R - where is the flex plate bolts located? sorry I'm just trying to picture where they are (not to good when it comes to trans information), is it behind a cover or something to access them somwhere near the pan?

XGarfX said:

Sorry I meant idling in gear as in moving without giving it gas. I think its the centering ball in the rear driveshaft, I'm gonna remove it and see if the noise continues. I did mess up some of the needle bearings during a u joint install and believe I mangled up that little spring inside the center ball. I didn't think much off it when replacing the joint and just put the bearings back together, the spring should of been replaced but it was super late and I was getting delusional.... stupid me. I have a spare driveshaft that I will take the centering ball out of and toss it in my rear xj shaft that has all new u joints in it.

Casey-R - where is the flex plate bolts located? sorry I'm just trying to picture where they are (not to good when it comes to trans information), is it behind a cover or something to access them somwhere near the pan?

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Is this the same noise that i heard at rausch?

well, that would do it. the torque converter bolts are behind the plate between the oil pan and bellhousing. if memory serves correct you have to pull the starter to get the plate off.

Sounds exactly like the noise I had when the centering ball on my rear double-cardan driveshaft went bad (assuming you have an SYE). Pull the rear driveshaft and rotate the CV part of it and I bet it has a ton of play in it.


Edit: I see you already came to that conclusion. Let us know the results.

Chris it might just be THAT noise! Its getting really annoying so I'm gona give it a shot this weekend and see how it goes.