gvns8

I just rebuilt my front drive-shaft with new u joints and centering yoke, and installed control arm drop brackets hoping to fix the front end vibration I have. When I remove the front shaft the vibes are gone. I have an lp d30 which make the pinion angle steeper than most xj's so I am thinking I have to buy some adjustable upper control arms so I can aim the pinion higher. But before I do so, is there anything that I'm missing?

I definitely do not want to buy adjustable uca's just to find out something else is the culprit.

The Black

do a transfer case drop. 1"

gvns8

I tried that but it didn't help. I really would prefer not to do that also since I have an SYE and I would loose ground clearance. I am running with no sway bars also, so I guess those might normally keep the pinion from pointing further downward with acceleration. Maybe if I get the correct length sway bar discos for my lift they might help. I only notice the vibes above 35mph and they get worse as I go faster-maybe due to the pinion being pushed downward further as the axle wraps slightly.

The Black

Did you get the drive shaft balanced?

gvns8

No but I had the same problem before I replaced these joints and when I was using a different shaft, so I didn't think that balancing it could make too huge of a difference since the other shafts were balanced. I also ran this front shaft in the rear and it was fine. The vibrations I have now are really bad- much like before I had an SYE or tc drop in the rear.

Gorillaxj

if it is gone when you take the drive shaft out, and you say the drive shaft is good. then it has to be something at either end. either the pinion bearings are supper shot, the yoke is loose, the output on the t/case is loose, or the bearings for the t/case output are bad. because putting the drive shaft in only allows the load to transfer threw the shaft. And again, this is going off of the shaft being good. which new parts aren't always food.

I would have the shaft balance checked, the ball joint in the CV portion of the shaft checked for play, and check both mounting locations I.E. yoke/diff, t/case.

I don't see how control arms would fix this unless you axle is flat and you are lifted high. how much lift do you have?

gvns8

The biggest reason I am hesitant to go for the adjustable UCA's is that I don't hear too often about people having a front drive shaft vibration-usually its only the rear. I guess it's just because most people don't start with a 3.5" lift and slowly progress to 5.5" of lift like I did.

gvns8

I have about 5.5" of lift. I replaced that entire ball joint/yoke in the CV portion of the shaft.

Edit:
I was also assuming that with a cv shaft in the front, the axle should point parallel to the shaft just like my rear axle is with a cv shaft. Here is the front through

Gorillaxj

huh. I have been fighting front drive line vibs on my 2000 Cherokee. 3 drive lines in the past year... in all 3 the CV joint goes out, cant wait to have unlocking hubs to keep it from spinning all the time. anyways...

It looks normal to me. the hard part about adjusting the uppers to compensate for pinion angle is that you roll it to far and caster goes out of spec, and can also create some other issues. I guess at this point I would crack your front diff cover, look at you spider gears, change the fluid, and make sure the pinion isn't loose as well. I guess I am out of ideas. maybe someone els can chime in. good luck. post up if you find something.

where did you get the stuff to rebuild your driveline from?

EDIT-also, have you tried putting your rear shaft on the front? or front shaft on the rear to see if it fallows the shaft or not? (just saw you had a SYE)

gvns8

Thanks for your help man. I am finding a lot of info on this on naxja, and the solutions seem to be basically a compromise between proper castor and proper pinion angle. I will check out the pinion for sure to make sure it is not loose. Thanks for that pointer. I can turn both the t/c and pinion yoke pretty easily, but I guess the question would be whether they can be moved side to side right?

Poloboy406

You can run a multiple double cardan cv from Tom Woods... they cost around an arm and maybe two legs ($400-500), but it would fix your problem.

They have the double cardan joint on both ends of the shaft.

Metmknice

Maybe have your d-shaft balanced..

sanchezcruz_20

Can you describe the vibrations at all? Do they have a cyclical sound?

I had front driveline vibrations which were also alleviated upon removal of the front drive shaft. Eventually, I came to the conclusion that my front pinion angle was in need of adjustment. I already had adjustable control arms so the procedure was pretty straight forward, but I documented the process in my build starting on page 26. I even took a few measurements before and after with an angle finder, perhaps you could get back to us with your numbers?

Raising the pinion resulted in complete resolution of the vibrations for me.

gvns8

I can't get the measurements until Tuesday, but I will check out your build, Do you have a low pinion or a high pinion? Also was your steering affected? I hear it can throw off the castor by doing this and cause your steering to wander.

Another idea I have is that the axle may be slightly wrapping as I accelerate, causing the pinion to go further down as I go faster. You see, when I used to have 4.5" of lift, I would have nasty vibrations in the front if I went on the freeway with swaybars disconnected. Once I put them back on the vibes stopped, which makes me think that maybe the sway bars kept the axle from wrapping and lowing the pinion down. My current sway bars are meant for a 3.5" lift, so I need new ones to fit my 5.5" lift. Right now the vibrations only start as I get to a speed past 40mph so maybe it is at this speed that the axle wraps enough to make the driveshaft vibrate. I am in 2wd though so I am not sure if my train of thought makes sense.

*Also I will try trading my front and new custom rear drive shaft just to make sure it is not the shaft that is the problem.

GooN

This is so weird. This is the exact problem I am having!!! I can't wait to find out what it is for you.