New Vibrations.

[USMC 0369]

Well, I finally got the ol' girl home. But whilst driving it, I find I now have some wicked vibration in the drivetrain somewhere. It doesn't impede the handling or steering, but it's worse when I'm at low RPM's in higer gears. Like when I try shifting into third when I come out of a corner and I'm not going quite fast enough yet for third. (Erik, I know the easy fix is learn to drive. ) I'm hoping to link up with Michael (Nagal) and take it out on our FIRST EVER offroad trip. (edit: oops, forgot Michael is out of town for a few days.)

I figured Rick or Erik would know maybe what's wrong, how to fix it, or what to check first to figure this out. I'm pretty stoked to have it 99% done. I still have to weld the mounts to the frame after some driving offroad to make sure it's "settled in".

[nagal]

Make sure the tires are balanced.

Yes we will hook up once I get back to town.

[USMC 0369]

Make sure the tires are balanced.

Yes we will hook up once I get back to town.

YAY! Cant wait!

[rick]

Rear driveshaft is my bet. Have you checked the ujoints in the driveshaft to make sure they're ok? Chances are you need to space the transmission crossmember down a bit to make the driveshaft angle better. You put 3" lift springs on, correct? That's enough to do it on a CJ-5. My 7 did it with 4" springs until I spaced the crossmember down about 5/8". Alternatively, pony up the $300 and get a CV shaft. Or you could install a 2" body lift, fabricate some motor mount lift brackets, and point the tcase output shaft down that way. That will also set you up to put a flat skid under it after you get your clocking ring to rotate the tcase up out of the way . I have an old tcase drop kit laying in the garage, but I'm not sure if your crossmember bolt pattern is the same. Otherwise you can just use some washers between the crossmember and frame and see if it helps before buying anything.

[USMC 0369]

Rear driveshaft is my bet. Have you checked the ujoints in the driveshaft to make sure they're ok? Chances are you need to space the transmission crossmember down a bit to make the driveshaft angle better. You put 3" lift springs on, correct? That's enough to do it on a CJ-5. My 7 did it with 4" springs until I spaced the crossmember down about 5/8". Alternatively, pony up the $300 and get a CV shaft. Or you could install a 2" body lift, fabricate some motor mount lift brackets, and point the tcase output shaft down that way. That will also set you up to put a flat skid under it after you get your clocking ring to rotate the tcase up out of the way . I have an old tcase drop kit laying in the garage, but I'm not sure if your crossmember bolt pattern is the same. Otherwise you can just use some washers between the crossmember and frame and see if it helps before buying anything.

Haven't really crawled under her to check the ujoints as I'm not totally sure what I'm looking for in a bad U-joint. Yea, it's that noob thing again. The tranny crossmember (pic below) is already lowered by the guy who owned it prior. Not a really 'classy' job of it, I know. The company that makes the springs SAID they were supposed to lift the Jeep 3", but measuring the shock mount difference (before moving the mounts) only showed about 2". I'll have to look up what a CV shaft is... (noob thing again). The rear driveshaft angle is okay the axle IMO, but at the T-case I'm not sure (pics below).

"That will also set you up to put a flat skid under it after you get your clocking ring to rotate the tcase up out of the way ." Uh... what? You did that on purpose didnt you... :dunno:

Hope to pick on your brains more soon. Michael and I might go out locally this weekend, once he sees it I may know more about what I'm talking about... :tongue:

Okay heres some pix...
This is the Rear at the Tcase and at the axle...
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This is the front at the Tcase and at the axle...
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And the Tcase "lowering job"...
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Okay, so I need to CLEAN under there!!!

[rick]

I think your problem is the degree wedges are too high an angle. It looks like at the axle yoke the driveshaft has almost no angle, or is actually pointing toward horizontal a bit from the axle pinion. Then at the tcase you have a down angle also. You should have the driveshaft pointed up slightly from the axle pinion angle and down from the tcase by about the same angle if possible. Think this: _/ at the axle, but not horizontal on the pinion. The way you have it set up would be great if you had a CV driveshaft.

[TDS SD]

Driveline 101

Here is a link to correcting your problem. It is well written
http://www.4crawler.com/4x4/CheapTri...line-101.shtml

[USMC 0369]

Here is a link to correcting your problem. It is well written
http://www.4crawler.com/4x4/CheapTri...line-101.shtml

Awesome! I needed something like that (barney style) to help explain what I'm doing. I did lots of google searches for CV driveshaft and only got ebay ads and people asking if they need to install one or not, nothing that explained what it is. Thanks man! And my education continues...

[rick]

Good link, lots of info there. I noticed that 4crawler.com makes light of the operating angle of a CV shaft... You need to point the pinion right at the tcase output (or slightly below to compensate for spring wrap under load) if using a CV shaft.

See here for a pic: www.4xshaft.com/techinfo.html

rick

[USMC 0369]

Good link, lots of info there. I noticed that 4crawler.com makes light of the operating angle of a CV shaft... You need to point the pinion right at the tcase output (or slightly below to compensate for spring wrap under load) if using a CV shaft.

See here for a pic: www.4xshaft.com/techinfo.html

rick

It seems I have new problems to deal with as well. This is all great stuff! I understand a lot more about the alignment of driveshafts, thats for sure! I assume I can just shave off some of the shims that came with the kit? I recall you saying that I should lower the Tcase about 5/8"... but the Tcase is lowered much more than that already, perhaps too far? I'll be dropping all of this to work on the rear main anyway perhaps I'll not put all the Tcase shims back in when I remount? Or get that CV shaft (which would be what I'd prefer, but $$ ya know) as the pinion is pointed straight at the Tcase right now. All of this discussion has been about the rear shaft, does the front play into this also? I'd say the front angles are more severe than the rear right now.