Rear End Shaking in 3rd gear - JeepForum.com
 
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post #1 of 9 Old 02-02-2015, 12:52 PM Thread Starter
HaydenBradbury
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1991 XJ Cherokee 
 
Join Date: Feb 2015
Location: Nashville
Posts: 5
Rear End Shaking in 3rd gear

Hello! I got my first jeep about 2 months ago as a trail/offroad vehicle and it is a completely stock 1991 Xj with 85k miles. I found it on craigslist and it has sat for 5+ years, I have been catching up on the general maintenance that is required but I have ran into one issue that I can't find the origin of the complication from.

Issue: So when you start it up, its great, everything sounds normal, no vibrations or anything. Then when you start driving, it is very smooth and how it should be up until 3rd gear (typically about 35mph). Once it gets into 3rd the whole time you have your foot on the accelerator the back end shakes, take your foot off the accelerator and it stops, mash your foot down on it and it also stops. it just does it when you are giving it a little gas. Has anyone dealt with a similar issue before because I am not sure if it is the transmission or the exhaust (catalytic converter possibly?)

I have had a few people tell me it is the torque converter, some say its the tranny, and some say its an exhaust issue.

Any thoughts or ideas would be greatly appreciated, thanks!


1991 XJ Limited
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post #2 of 9 Old 02-02-2015, 01:26 PM
1stockjeep
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1993 XJ Cherokee 
 
Join Date: Feb 2009
Location: modesto CA
Posts: 1,135
Could be a tire that needs balanced or a driveshaft issue. First check the obvious stuff like tires for in even wear and have a look at u joints. Also check the pinion bearing by moving the drive shaft up and down.
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post #3 of 9 Old 02-02-2015, 01:33 PM Thread Starter
HaydenBradbury
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I am positive that it isn't the tires, but I will have a look at the u joints and pinion bearing when I get home. Thanks!
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post #4 of 9 Old 02-02-2015, 01:44 PM
foreveryoung001
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Quote:
Originally Posted by HaydenBradbury View Post
I am positive that it isn't the tires, but I will have a look at the u joints and pinion bearing when I get home. Thanks!
Did you change them up from the ones that had been parked for 5 years? If not, you are almost sure to have flat spotted tired... but yes, check the u joints and pinion for play. Also, you might want to check the transmission mount. If that rubber is deteriorating, it can cause some pretty odd vibes in the drive train.
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post #5 of 9 Old 02-02-2015, 02:13 PM Thread Starter
HaydenBradbury
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1991 XJ Cherokee 
 
Join Date: Feb 2015
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Yes I changed them from the ones that were on the car when I bought it, those things were so rotted that it was dangerous to drive anywhere on them haha

1991 XJ Limited
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post #6 of 9 Old 02-03-2015, 01:41 PM
sAe23
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1995 XJ Cherokee 
 
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Location: Los Angeles / SFV
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Have you tried rotating the tires front to back?
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post #7 of 9 Old 02-04-2015, 09:14 AM Thread Starter
HaydenBradbury
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1991 XJ Cherokee 
 
Join Date: Feb 2015
Location: Nashville
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Quote:
Originally Posted by sAe23 View Post
Have you tried rotating the tires front to back?
I haven't tried rotating the tires, I replaced the stock tires with some tires from a '93 XJ and they have about 85% tread left. I can tell you that the shaking is not coming from the tires, it's the body shaking, and it is pinpointed to underneath the back seat, so like middle of the car. (I guess saying that the rear end was shaking was the wrong terminology)

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post #8 of 9 Old 02-04-2015, 10:44 AM
sAe23
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Well then, how about... bad U-joints, dented driveshaft, driveshaft missing weights, problem with T-case output (shaft/bearing).
Do you feel comfortable with removing the driveshaft and driving it in 4Hi to see if the symptom changes?
You'll need to wrap or cover the T-case hole to prevent fluid loss...


...hold on...


You said it was "completely stock", yet your profile says it has a 3.5" LIFT?!?
If this is true, you probably just have the common vibrations that come with not having proper driveline angles...


Please clarify!
(And try the suggestions regardless)
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post #9 of 9 Old 02-05-2015, 08:41 AM Thread Starter
HaydenBradbury
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1991 XJ Cherokee 
 
Join Date: Feb 2015
Location: Nashville
Posts: 5
Quote:
Originally Posted by sAe23 View Post
Well then, how about... bad U-joints, dented driveshaft, driveshaft missing weights, problem with T-case output (shaft/bearing).
Do you feel comfortable with removing the driveshaft and driving it in 4Hi to see if the symptom changes?
You'll need to wrap or cover the T-case hole to prevent fluid loss...


...hold on...


You said it was "completely stock", yet your profile says it has a 3.5" LIFT?!?
If this is true, you probably just have the common vibrations that come with not having proper driveline angles...


Please clarify!
(And try the suggestions regardless)
Thanks for the advice, I guess I got a little post happy with my profile, all the upgrades I listed on my profile are ordered from Quadratec/4 Wheel Parts but they haven't arrived yet Currently it's bone stock, just trying to weed out all the issues before I go any farther into modification. Thanks for the advice though, I will check everything you mentioned when I get home from work. Thanks!

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