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Pulled front driveshaft and vibration is gone...

V

viperbluelx

NAXJA Forum User
Location
Ringgold, GA
So this whole time I've been thinking the vibration was coming from the rear driveshaft. Well today I pulled the front driveshaft completely out and the vibrations were 75% gone. So I get back to my shop and check the u-joints and sure enough a few of them didn't move smoothly as if they were dry or wore out. So I replaced all 3 u-joints with new ones(what a pain). I marked everything when I took it apart so I'd make sure to put it back together correctly. I install it and take it for a drive and the vibration is back and just as bad. I have an 01 with the low pinion D30 in the front and only a 3" procomp lift with a 1" TC drop. I did have a very slight amount of up and down movement in the front slip but I greased it and it really seemed to tighten it up but it still vibrates. Is the TC drop throwing the angle on the front off while helping the angles on the rear? I tried removing the TC drop last week and the front driveshaft made all kinds of noises and acted like there was slack in something in the front end when you'd go from coasting to accelerating, when I put the TC drop back on those issues were gone again.
 
switch to a hi pinion..that should really help
 
It's my daily driver and I don't really want to get into doing a swap, I wonder if adjustable upper control arms would help so I could point the pinion directly at the TC.
 
Don't point the pinion right at the tcase, but a degree or so below.

Check your slip shaft as well.
 
or just man up and get over the vibrations...
happyfinger.gif
 
doesn't seem to be an issue for many, but ive my friends and i have a pile of about 5 driveshafts with worn out slip joints that are now no good. you can replace u-joints, and rebuild the CV joint all day long, but once the slip joint gets play in it, the shafts toast. no rebuilding that.

get you some control arms for the correct amount of lift, and thatll take care of your problems it sounds like
 
It's a procomp lift with chromoly lower control arms that you'd think would have the pinion pointing correctly already. How do I check the slip yoke?
 
viperbluelx said:
It's a procomp lift with chromoly lower control arms that you'd think would have the pinion pointing correctly already. How do I check the slip yoke?
Click to expand...
Push up and down on the shaft and check for play in the telescoping center. my sisters 01 xj had the same problem.
 
hm, i asked a few of my buddies if they'd ever heard of slip yokes wearing out... and they hadn't but i was 95% sure that mine is toast becasue i can do just what you are describing... already have a line on a new one.

to the op: are you sure the shaft is still balanced? i know you said you were careful when you took it apart... but what if a weight fell off way before?
 
Hi there,
I had the exact same thing happen when I lifted my 01 XJ that has a low pinion D30 and a TC drop. When I removed the front shaft the vibes went away. At first I thought the front shaft was shot because of some looseness in the splines but then I got to thinking "why wasn't this causing problems before the lift" so I kind of ruled it out. I measured my front pinion angle and found that with the fixed length extended lower control arms supplied with my kit the pinion angle was thrown way off. So I went ahead and purchased some adjustable upper control arms. I adjusted them so that I retained about 4° of castor angle and that was sufficient to cure my front driveshaft vibrations. To this day my front shaft still has some play in the slip splines but I don't feel any vibrations at all. Just keep it well greased.

Note that I daily drive my rig and retaining a minimum of 4° castor is important so the steering returns to center.
My 2 cents!
 
Last edited:
One good indicator that the slip joint is worn out is some plastic looking pieces hanging out of it. I forget exactly what the part is, but I noticed mine had a little something sticking out, and when I took my shaft to a local shop, the guy said the joint was toast.

Drove home on the highway without the front shaft after that, and was amazed the slight vibrations I was used to were gone.
 
Man, I went through this exact same issue on my last 99. I rebuilt the driveshaft, bought adjustable control arms, checked my angles, replaced axle u-joints, balanced tires, rotated tires, etc.. I never could eliminate it even after throwing all that money into it. Finally I just pulled the front driveshaft and only put it in when I went wheeling. I was driving 100-200 miles a day though.
 
viperbluelx said:
Hmm, so maybe I need to measure castor before buying adjustable uppers.
Click to expand...


Castor in itself is not what is causing the vibes. I'm pretty sure the pinion angle is.
If you measure out castor to be for example 10° then you can buy adjustable uppers and rotate your axle forward 6° and still have an acceptable 4° of castor.

But.. if you measure your current castor to be 5° then it's not worth buying adjustable uppers to gain an extra 1° of pinion angle while still retaining 4° castor.
 
no, it doesn't just get an angle finder and find the angle from the ball joint axis to vertical. you want about 5 towards the rear of the vehicle.

vibes are probably not the pinion angle... i said probably, so don't take that as bible. i'd check u-joints, the double cardan, or the slip yoke first.
 
Are the yoke ears on the axle end of the driveshaft in line with the yoke ears at the other end of the shaft? It is possible they are out of sync too. Or the driveshaft is dented and unbalanced now. Check both.
 
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