rgr4475

98 4.0 AW4

Getting some vibrations under my feet at highway speeds. Went under to check the u-joints and when I grab the rear drive shaft to check for u-joint play, the whole transfer case seems to move up and down slightly. I can take a video later but is this normal?

SteveMongr

Likely the motor/transmission mounts. Look for the movement to be above cross member at transmission mount.

93_xjcherokee

Transmission Mount. I just replaced mine. Took about an hour

ThunderThighs

What part did you go with? I'd like to replace mine

rgr4475

So the transmission mount did need replacing. Did that and now I am getting a pretty harsh vibration which sounds like it's coming from the left side of the engine compartment (sitting in the seat). Now what?

rgr4475

Looks like the drivers side motor mount is bad. I'm guessing it's been bad and haven't noticed it because of the old trans mount? Or the new trans mount caused it reposition and go bad. I dunno. Either way looks like I'll be replacing the motor mounts. Found a video online to go by, so wish me luck.

rgr4475

Got the motor mounts in. Had a little trouble getting the drivers side back in but the passenger side went in easy. Vibration is gone. Thanks all for the help!

93_xjcherokee

Sounds like what happened is the trans mount was bad so it caused the weight of your motor to mask the fact that your motor mounts were also bad. Glad you got it Done. I need to do mine too as soon as I can afford it

SteveMongr

Good job, all in the same day! Usually folks do not jump on the repair/fix, and question the diagnoses, and question where to get parts and it takes them days.
Forgot to mention, as a rule replace all 3 mounts when one is bad. You figured that out too. Kudos to you

rgr4475

Thanks guys. Yeah I quickly saw the drivers side motor mount was bad so since I was dirty and the tools were out there was no sense of waiting. Just went to the local NAPA and got the parts which were cheap.


I am now noticing a slight vibration at idle while in gear and a slight vibration when i accelerate from a stop. Is that because of the new position of the engine and trans with the fresh and taller mounts? Is that something that settles after a little time?

SteveMongr

Likely culprit is the exhaust where it passes over cross member, it's a tight fit. The wear part is the rubber insulator/isolater adjacent to transmission mount.
When transmission is engaged, motor torque causes a shift of engine and exhaust. Keep this in mind when inspecting for clearance.
https://www.cherokeeforum.com/f2/cro...hanger-196774/

rgr4475

Thanks for the picture and link. So just to be clear, the shift of the engine and trans and weak rubber for the exhaust causes the exhaust to rest against the body or frame thus creating the vibrations?

chefftomain

Look at the cross member that holds the transmission mount up, and if you see the exhaust system mount bracket is really close to touching the cross member then you have a bad transmission mount. Over time it will sag and everything will rest on the cross member and cause your jeep to shake in any gear even park. Seeing how even the newest XJ is still over 14 years old it is your best be to replace it, rubber rots, especially if you live in the Midwest where you deal with salt, rain, freezing temperatures, and the hottest days you can ever remember. I believe that O'Riley's Auto Parts has it for around $35 with tax.

Here is a link with pictures that explains everything I just said with pictures and how to replace it.

http://www.jeepforum.com/forum/f11/b...ement-1046436/

rgr4475

Thanks for the reply. I replaced all of the mounts the same day as I made this thread. Took care of the problem.