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driveline angle querry

riverfever

NAXJA Forum User
I put a BB on the 01 months ago that consisted of shackles and spacers. When I test drove it after the install, it did have some very mild vibes. My 96 gets driven the most so I never dealt with it until this rainy day. I measured the driveline angles. TC output was 5 degrees and the pinion was 12 degrees. With no SYE and CV, I know I want those 2 angles parallel. I had a TC drop kit and 6 degree shims. I opted to go with the shims. I out them in and re-measured the angles and was almost dead nuts on. Test drove it and the vobes were horrible. I'll go back tomorrow morning and do the TC drop. I'm not crazy worried about this but my question is this:
The numbers don't lie. According to my results...the current configuration should work. I only ask this b/c there have been times when a new forum user has asked a question with this same scenario. I know I've answered several threads dealing with this. In no way am I ever trying to be a d!ck when I tell them that we need to know the angles. I always try to be polite. BUT...if I was a noob with these angles....I'd be a little curious. Any thoughts?

-river
 
ok maybe im dumb but 6* shims sounds ridiculous for a BB

i have 3* shims on my RE 3.5 inch lift on my '91 and i think it's too much

t-case drop should probably cure it just fine...if not add like 2* shims to it or something

also, what rear end do you have? d35 or 8.25?
 
You guys aren't dealing with my question though. Every Jeep is different. 6 degree shims may sound like a lot but you only know what to use b/c of the angles. Yes, I'd rather do shims over TC drop but it still doens't tell me why, if my angles are good with the shims in place, I still have vibes. Again...the numbers shouldn't lie but I think they just did.
 
For a standard two joint drive shaft (stock xj) the centerline of the pinion on the diff and the output shaft on the TC should be parallel. You are adding shims and causing the problem to become worse. A TC drop will lower the output shaft of the TC but still remain parallel with the pinion on the diff. Go to the Tom woods website and check out the tech info for a picture.
 
Again...I know what the angles should be and I'm telling you that without a TC drop or shims the angles were NOT parallel. Putting the shims in put the angles within a degree of each other and, thus, much closer to being parallel than they were before but resulted in worse vibes.
 
If you stay with the standard driveshaft, you may hve to go with the trans drop kit (really just 1" spacers and longer bolts) to keep pinion and tras output parellel.

If you go to a slip yoke eliminator and double cardan driveshaft (I'm using a second front driveshaft), then you point the pinion at the trans output, using shims.

With a BB (2"?), I wouldn't think you'd need either one.

How's your U-Joints?
 
That's my question. You can attain parallel angles by doing the drop kit OR shims. I would have rather done shims and not lost clearance but it didn't work. I put in a drop kit today and it rides perfect now. The 01 doesn't get wheeled at all, in fact, it hardly gets driven. U joints are fabulous. The lift WAS only 2" but it did need some help.
 
how did you measure the angles? tool, and position of such tool when measured. what shouldnt' be the case in your situation is that the u-joints are maxed out and binding giving tremendous vibes and near future failure. my sugestion is to double check you measurements 6* does seem like a lot even though all jeeps are supposedly different. pics are always helpful
 
riverfever said:
That's my question. You can attain parallel angles by doing the drop kit OR shims.
True, but you're overlooking a few things. With the lift and shims your u-joint angles may have been parallel. However, the operating angles of those u-joints will be sharper than they were pre-lift. Your joints may have been the cause of the vibes simply because they were running at new angles...changing them out may have reduced a majority of the vibes when combined with the shims.
 
This is all rather new to me but, when I lifted my '96 with Rusty's 3" kit with full rear packs (which give the rear 4" BTW) I first added 3* shims and had slight vibes, then dropped the trans 1" and now no vibes. This seems like a lot to me but when you consider that the slip joint is at the t/box my thoughts are that the straighter the d/shaft is then there is less resistance to the actual slip motion of the slip joint due to both angles being less. If this just sounds like so much BS ... i'm sorry but hey its just a thought, then of course we have to consider spring wrap ... I guess the only real answer is (at least for me) SYE + CV d/shaft = the only sure fix. Don't ask my angles as I haven't measured yet, waiting for all to settle fully then maybe I'll measure - but, like I said - no vibes. Hope this makes some sense.

Mike
 
Wondering if someone can say how they measured the pinion angle? The driveshaft angle was easy enough to get..i can't seem to clamp onto anything to get the pinion angle. Just trying to figure out how much shim i need (RE 3.5" w/ 3/4" t-case drop). Thanks.

http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Single-Cardan-Measurements

Angle01t.jpg


Angle02t.jpg
 
Roll the vehicle forward or back until the u joint caps that sit in the pinion yoke are at 12 and 6. Take a large c clamp and clamp a piece of flat stock to the yoke. Then I place the angle finder so the magnet is pointing up, and contacting the underside of the flat stock. Make sense?
 
I just measured it. 19* on the driveshaft and 79* for the pinion. If my math is correct (90*-79*=11*...19*-11*=8*). So i need an 8* shim (and obviously a SYE/new driveshaft ASAP)?
 
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