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post #1 of (permalink) Old 04-12-2003, 10:15 PM
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Drive shaft vibration?

I blew out my rear u-joint and I think I may have bent my output shaft. I have two driveshafts with new u-joints and with both of them I have a vibration that is much worse than the usual teeth chattering that occurs in a Jeep. I'm planning on putting a Tom Woods tailshaft conversion kit in it. Since I don't know a whole lot about that conversion I'm not going to put it in until I shop around a bit more, but in the meantime will I risk burning up bearings in my transfer case, or just burn up more u-joints? And is Tom Woods who I'd want to go with? Or are there better choices out there for the same price or maybe a little more? (better for less isn't bad either) [img]images/graemlins/smile.gif[/img]
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post #2 of (permalink) Old 04-13-2003, 02:02 PM
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Re: Drive shaft vibration?

Well, being that you have 2.5' of suspension and another 2' in shackle, my question would be to you. Did you use a X-fer case drop? If not with 4.5 inches of lift that will cause terrible angles and I dont know about bearing in you xfer case but I do know that you can smoke through those U-joints pretty quick. Also. Did you use shims on you rear springs to help the axle "squat" and turn up a weeeee bit. That can make a world of differance also.
post #3 of (permalink) Old 04-13-2003, 03:23 PM
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Re: Drive shaft vibration?

1. Casey, welcome to the forum.
2. Thanks for filling out your user profile.
3. Read the New Posters Message at the top of the forum.
4. Participate more often!
5. Two brains are always better'n one!
6. What HoOkeD's said I couldn't say any better.
4. You've got about 3.5" of lift, on a good day,
5. If you've not made accommodations for the drive-shaft angle,
6. The drive-shaft will vibrate your teeth outta your head.
7. I'd doubt the input shaft is bent, but
8. Rotate it... and see if it's[*]Binding [*]Rotating out out of round
9. If there's a bind or it's rotating concentrically,
10. There may be a problem.
11. Don't give up yet.
12. Without alterations to the drive-line angle
13. You'll continue to destroy the U-joints.
14. Tom Woods is a good vendor,
15. But shop locally.
16. A good drive-shaft shop can fix you up,
17. For about the same price and you save shipping.
18. You can:[*]Drop the transfer case [*]Raise the pinion angle [*]Install cardin joints [*]Mix and match the above.
19. It's a matter of learning what you need to do,
20. And doing it within your budget.
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post #4 of (permalink) Old 04-13-2003, 08:34 PM
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Re: Drive shaft vibration?

I do have a transfercase drop kit on it. I honestly don't know how bad the vibration was before I blew out the first u-joint. I had just bought it (my jeep) a couple months before but my brothers and father (all Jeep owners and enthusiasts) told me it was much worse than before I blew the u-joint. (i don't know for sure) As far as the shimms go I am not sure. (I don't know alot about lifts, all I've had was a Jag XJS V12 and a Corvette, not a whole lot of shimms in those, never any vibrations either [img]images/graemlins/smile.gif[/img] ) But if my output shaft WAS bent, will I trash my x-fercase or is it ok for the next month or two till I put the conversion in it?
Thanks for all the suggestions so far. I'm gonna look at the receipts for the lift next week and find out exactly what was done. (i am in mexico, all paper work in AZ)
Thank you
post #5 of (permalink) Old 04-14-2003, 08:12 AM
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Re: Drive shaft vibration?

OK, It's my understanding that unless you've already got the CV joint setup, you still have to check the angles even with the transfer case drop. My understanding is that the drop mostly changes the transfer case output shaft angle (not the front of the drivetrain, like the engine). Ideally, not only should the transfer case point down ata good angle, but the rear diff should point up at an equal angle. This is because the action of the "bent" u-joint causes the rotational speed of the shaft to vary as it turns a full circle, and it requires an equal "bend" in the other u-joint to cancel that factor out and turn the diff pinion at an even rotational speed. the diff drop will lower the angle, but if your diff angle was matched to the transfer case before the drop, the diff angle might actually be too high.
If you've had the drop for a while with little or no vibration, and it's just started with the u-joint replaced, then it's probably not the above scenario. Maybe check the u-joint caps, that they're not tapped down too tight. You want the u-joint to be able to move easily. If you've got zerk fittings on them, grease 'em. Maybe that might cause vibration, I don't know, I know it'll wear on your u-joints at any rate. Check the u-bolts (or sissy strap 'n bolts if you've got 'em, seems like I read that you should swap for u-bolts if you can), make sure they're tight but not pinching the caps. Those are some of the things I'd do first, before messin' with the transfer case. Anybody, correct me if I'm wrong, I'm still learning this stuff too.
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