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Alright just did u joints in rear drive shaft but nasty vibration still happens?

G

groovyjeepster

NAXJA Forum User
Location
Libertyville Il
So I have a 1990 jeep cherokee, 4.0, aw4, np231, dana 30 and 35. So this weekend I got new U joints in my rear driveshaft. The old ones had some play in them so I thought that was it. But I was wrong. So this is what happens. When I get up anywhere between 35mph and up I get a bad shimmy coming from the rear end of the vehicle, it even seems to loss power for a second. As I ease off the gas it goes away. And it doesn't do this all the time. Sometimes I can be going around town doing 50 all day and not have it happen once. So guys any ideas for me too look next? I did just chanced the diff fluid not to long ago in the 35 and everything seemed good no metal shavings or anything. Fluid was really dirty, looks like it hadn't been changed for a long time. This happened before I changed it too. Thank you for your time.

al
 
lug nuts tight and centered on wheel? wheel weights sliding around? crazy i know,but i`ve had it happen to me. drove me crazy because sometimes it was fine,others,not.
 
did you put the blocks in? was the vibration there before it was lifted? every jeep is different, some can go a lot hight with no vibes than others, for example, i have a 97 with around 5 inches of lift, and no vibes, but I know people that did only a budget boost, and had vibes....
 
I had no vibes before the blocks. I did but them in but then I had it at a shop to have them but back in my helper springs with the blocks and even after that I had no vibes, It wasnt till a few months after when I had to replace my transmission I started getting vibes. The transmission is great! So I don't believe it to be any tranny problems.

By the way nice jeep bgwyllys61.
 
thanks for the compliment! Im wondering if it isnt something in the tranny mount....my dad had a bronco 2 that i used to borrow quite often when i was younger, and it did the same thing that you speak of, vibes sometimes, but not always, and it turned out to be the tranny mount. It itough to diagnose vibes via the internet, but im sure if you just keep checking things you will find it.

also, check the pinion and see if there is any play there, put the jeep in neutral, and take the pressure off the driveshaft, or take the DS out, and see if your pinion has any movement, it could easily cause what you are refering to
 
When was the last time the transmission mount was replaced with a new one?

If you can't remember, or don't know, it may be time.

Have you re-checked the torque on all the bolts that were removed for the transmission change?

Did the problem only start after the gear oil change? If so, sounds an awful lot like an LSD issue.
 
Haha well my driveshaft is fine, or it looks to be, I haven't knocked it on anything lately. Unless if the transmission guy dropped it. The vibes were happening before I changed the diff fluid. My trans mount isnt the best I know that, could that cause it to randomly vibrate like that? I'll check my transmission bolts and torque.
 
You might think about removing the frt drive shaft to eliminate it as a suspect. Also check the I.D. tag on the rear diff to make sure it's not a Trac-Loc (usually equipped with tow package option).
 
also , are your tires recently balanced? have you checked driveline angles? how old are your rear leaves? a 2" block would prob make old saggy springs alot worse when it comes to axle wrap. so if you have really soft springs and blocks you might be getting some wrap.....i second the trac lock check and pulling the front ds and checking the tranny mount and the motor mounts. also examine all suspension bushings. if your tranny mount isnt doing good replace it. maybe consider newer springs if yours are very old saggy, or replacing the blocks by building some bastard packs....really easy for 2"
 
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