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Unread 01-05-2013, 06:34 PM   #1
el scorcho
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More Vibration After U-joint Replacement.

1990 Jeep JY, 4.2L, 2.5" lift, daily driver


Earlier this summer, I replaced my worn motor mounts with Brown Dog mounts with polyurathane bushings; I also replaced the transmission mount with a new polyurathane one.

Fast forward to October, the Jeep has some vibration between ~45 and ~55 mph in 4th and 5th gear, then one day the drive shaft u-joint strap breaks. A bolt sheared holding the strap over the u-joint to the rear differential. I fixed it replacing the u-joint, straps and bolts; it ran great for a week, but it started vibrating again and the exact same thing happened. So, I fixed it again. But this time, I checked the bolts and u-joint every couple of days, no problems for about a 6 weeks.

Now, when the car is in 4th or 5th gear between 45 and 55 mph (1100 to 1500 RPM) there is MUCH MORE vibration and noise than before. I'm worried it's my transmission this time. Any suggestions on how to eliminate or confirm the transmission as the problem. Should I remove the rear drive shaft and go for a drive?

Thanks

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Unread 01-05-2013, 08:24 PM   #2
Dake
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I drilled out the yoke and put the ford U-bolts from the help section at advance. Have had that problem sence that was back in 93.
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Unread 01-05-2013, 08:29 PM   #3
Dake
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http://www.jeepforum.com/forum/f12/b...-bolt-1384119/
Like in post #13
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Unread 01-05-2013, 09:59 PM   #4
el scorcho
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Originally Posted by Dake View Post
No nothing like that. I got the remainder of the bolt out both times, strangely VERY easily; I simply turned it out with a very small flat tip screwdriver. About 6 weeks after the second u-joint replacement, the whole Jeep vibrates way more than when it was the u-joint and it's much louder. Also it started suddenly, unlike the u-joint which became noticeably worse over a few days. Both u-joints seem solid on the rear drive shaft. I totally forgot to check the transmission and motor mounts; I'll do that tomorrow.
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Unread 01-06-2013, 08:45 AM   #5
sdotcarter
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Sometimes loosining the tranny mount on the skid and retightening will help. Especially if they werent loose when u did your motor mounts.
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Unread 01-07-2013, 07:39 AM   #6
el scorcho
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More symptoms...

When I go over a bump or pothole, there seems to be a bit of vibration and noise from the tranny area. Also when in the problem range, I get vibration in the clutch pedal when it's pressed down and a little in the shift lever. I haven't tried removing the rear drive shaft yet to see what happens. Visually, all the bolts and mounts look good.

On some what of a side note, how long does the gear oil in the transmission last? My rebuilt transmission has about 100K on it without any servicing.
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Unread 01-07-2013, 08:26 AM   #7
sdotcarter
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Change it out to Walmart 10w-30
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Unread 01-07-2013, 11:45 AM   #8
95Turtle
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Something is making you blow through u-joint straps on the shaft. Could the shaft have lost a weight or gotten bent somehow so that it is out of balance? Vibrations can be hard to pinpoint and it seems like your problem is still driveshaft related due to all the broken u-joint straps. The vibes may have just gotten bad enough that now you can feel them in the shifter, clutch pedal, etc. It is possible that the new transmission mount is in a bit of a bind causing stress on the driveshaft. Also, how are you installing the u-joints? If you put them in with a hammer and sockets, sometimes the yoke gets "sprung" a little bit and puts stress on the u-joint so it will be tight in one direction, causing stresses in the shaft. Pull the driveshaft out and move both u-joints by hand to make sure they move freely in all directions. I would absolutely rule out the driveshaft before assuming that the vibes are coming from the transmission.

It is probably a good idea to change the transmission fluid just because it hasn't been changed, but I doubt that will help your problem at all.
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Unread 01-07-2013, 01:46 PM   #9
el scorcho
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Yup, slightly bent drive shaft, all yokes out of tolerance and the bearing caps were sliding in the rear yoke. Just got a brand new drive shaft with transmission and pinion yokes. Got my drive shaft at Randy's drive shafts in Houston, TX; they were very helpful, friendly and had it done in about an hour. Now I'll install the new drive shaft and change the oil.

Thanks everyone!
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Unread 01-07-2013, 07:33 PM   #10
el scorcho
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Let me back up to before I bought my new drive shaft. While showing a local transmission specialist what my car was doing, it started doing it in all gears right out of the parking lot. He said it's definitely the drive shaft because manual transmissions don't vibrate. I took off the rear drive shaft and the problem went away, that's when I went to the drive shaft shop.

They pressed in all the u-joints where it was needed on the new yokes. So I got the new drive shaft and pinion yoke on, but things are no better. It still clatters and vibrates in all gears except reverse. Did I mess up my rear differential? Did they screw up on the drive shaft (they do quite a bit of business)? Should I have replaced the crush sleeve? What's next, a real mechanic?
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Unread 01-07-2013, 08:24 PM   #11
95Turtle
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First thing to do is take the drive shaft off again and see if the vibes go away. Then you will know if the shop screwed up or not. You said you put a new pinion yoke on, but is there any slop in the pinion bearing? It is odd that it is now doing it in all gears. Is there a speed/rpm at which the vibration is worse? Does it get better or worse when you turn in certain directions? If you get going pretty fast down a hill and put it in neutral does it still do it? Answering some of these questions might help you narrow it down...
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Unread 01-07-2013, 09:19 PM   #12
el scorcho
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Originally Posted by 95Turtle View Post
First thing to do is take the drive shaft off again and see if the vibes go away. Then you will know if the shop screwed up or not. You said you put a new pinion yoke on, but is there any slop in the pinion bearing? It is odd that it is now doing it in all gears. Is there a speed/rpm at which the vibration is worse? Does it get better or worse when you turn in certain directions? If you get going pretty fast down a hill and put it in neutral does it still do it? Answering some of these questions might help you narrow it down...
It does it from take off. I quickly shifted to 2nd and 3rd not accelerating much, then I crawled half way up the block back home in 1st. I only got about 60 yards from the house. I pretty sure I didn't tighten the pinion nut enough, I not sure where I got it in my head that it only needed 70 ft.lbs.; I'll fix that in the morning.
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Unread 01-08-2013, 11:00 AM   #13
el scorcho
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Broken driver's side, rear leaf spring. I noticed it when I crawled up underneath this morning. I think happened a couple of days ago, when I heard a loud pop driving, thought it might have been a rock hitting the undercarriage. In all likelihood, the new drive shaft is just fine. Time to spend more money.
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Unread 01-08-2013, 12:15 PM   #14
95Turtle
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Good opportunity for a new lift
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Unread 01-08-2013, 01:14 PM   #15
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Quote:
Originally Posted by el scorcho View Post
Broken driver's side, rear leaf spring. I noticed it when I crawled up underneath this morning. I think happened a couple of days ago, when I heard a loud pop driving, thought it might have been a rock hitting the undercarriage. In all likelihood, the new drive shaft is just fine. Time to spend more money.
that was causing the vibration? or you still have the vibes?
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