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New Tranny Mount=vibration

B

brielly

NAXJA Forum User
Location
nj
01 cherokee 4.0 114k miles. I had some noise (creaking) and vibration so I swapped out the transmission mount. It was definitely needed. Now the noise is gone but the vibration is MUCH worse, as in not driveable. Recently I put in a used driveshaft as well but that had no effect. Front driveshaft is out to eliminate it from the equation.

1st question- Can you screw up installing a tranny mount? Was there a certain direction it needed to be in? It looked the same on both sides so I assumed no.

What else could cause the vibration to be so much worse with the new mount?
 
Do you have any lift installed on your rig? 97+ rigs are more prone to drive live vibrations. Your old mount may have sagged reducing drive line vibrations.
 
This is vibration during driving, and not at rest?

Check the bolts on the tranny mount, and ends of the driveshaft holding the U-joints in.

Is there any play in the driveshaft or spots where a weight might have come off?

When I took my '00 from saggy, inverted springs back up to stock height with new springs, the u-joints had "settled" in the old driveline position, and did NOT like it when I changed the angles, just a little bit! New joints made it very happy and took away the vibrations.
 
U-joints can wear at a certain right height and when the ride height changes (such as new springs/mounts) some vibes can occur. I know when I replaced the stock sagging springs on my XJ on acceleration it had some flutter for a few weeks. But it wasn't continuous and I wouldn't say not drivable. If the mount was "wedged" or "forced" into place it may be causing your problem. Normally you attach the mount to the transmission, put the crossmember on, and tighten the 4 stud bolts on the crossmember side of the tranny mount. If it doesn't go back neatly you may need to loosen up your engine mounts and move things around a small amount.
 
I do have the old drive shaft and it has new u-joints. I took it out because it did vibrate but it also did before the u-joints were done. The shaft may have been slightly damaged when removing the old joints because its a bit stiff when trying to move the yoke. I may swap it back in and see what happens. If that doesnt help Ill remove thr rear shaft, bolt the front back on and see what happens.
 
Polyurethane tranny mount? I tried one once and the vibration was awful. Swapped it back out for a factory-type rubber mount.
 
Did you get a centered, or offset mount? There are different mounts for different years, and I believe they'll both bolt up. The wrong mount would put a sideways angle on your propeller shaft.

Jared:patriot:
 
The 01 XJ takes a centered mount. To get an offset mount installed you'd have to get the driveline twisted a good bit.
 
I think I found the culprit. Upon further inspection, there is quite a bit of vibration at idle especially when I first start it up. I checked the motor mounts and sure enough there was quite a bit of movement when prying on them. The pb blasting has begun. Hopefully this does the trick.
 
I changed the motor mounts but no dice. The engine ran smooth in park but began vibrating badly when I put it in gear. I didnt even bother going for a ride. I guess I'm pulling off the new tranny mount and possibly replacing it with another. Anyone have any other suggestions? I'm stumped.
 
The new mounts are rubber. I drove it today and there's definitely still a vibration when accelerating 2000 rpm's is really bad. Its more noticeable now with the new mounts. It also vibrates more in reverse when standing still. In park its actually pretty smooth. There's no play in the t-case shaft or rear diff. The slip yoke has a bit of play up and down but I would imagine just by the ways it designed there would be some. I'm really not sure what else to check.
 
CarbonXJ said:
Define "a bit of play"

My stock slip yoke didnt' have any play in it.
Click to expand...
Maybe a 1/16 of an inch movement. The shaft itself feels solid. Both the original and used driveshafts have the same amount of play in that area.

I just removed the rear driveshaft and drove in 4wd. It was much smoother. Since I don't trust my original driveshaft I'm going to spring for new u-joints on the used one I picked up. If that doesnt work I guess it will be time to crack open the rear diff and have a look. I don't like where this is heading.
 
If you have the funds, have the shaft balanced after the new joints. Some shops will even check the balance for free. No dents or damage you can see on the stock shaft?
 
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