vibes at 45mph and up

Hi guys. Experiencing vibes in my front end from about 45mph and up.

92 xj 4.0, np242, d30/d35, 3" bds lift, new trackbar, brakes, hubs, shocks, and all steering linkage. Ball joints are fairly new also. Tires are fairly new bgt at's, balanced out perfect. Only old parts are the control arms and bushings, but they show no signs of play. Nothing shows any play in the front end and all the bolts are torqued.

I tried rotating the tires, didn't fix anything. I rebuild the front shaft a few months back with new ujoints and centering ball. Didn't fix anything. I pulled the front shaft last week and all the sudden no more vibes. Check the yokes on the front axles and tcase and they are tight with no play. SO I figured it was the shaft.

My local driveline guy went to balance the shaft and it was slightly off. Had the shaft cut, rewelded and fixed. Balances out beautifully on the machine. I put it back in, grease up everything and bam, vibes are back.

Any ideas why????

Whats your pinion angle?

87baseomatic said:

Hi guys. Experiencing vibes in my front end from about 45mph and up.

92 xj 4.0, np242, d30/d35, 3" bds lift, new trackbar, brakes, hubs, shocks, and all steering linkage. Ball joints are fairly new also. Tires are fairly new bgt at's, balanced out perfect. Only old parts are the control arms and bushings, but they show no signs of play. Nothing shows any play in the front end and all the bolts are torqued.

I tried rotating the tires, didn't fix anything. I rebuild the front shaft a few months back with new ujoints and centering ball. Didn't fix anything. I pulled the front shaft last week and all the sudden no more vibes. Check the yokes on the front axles and tcase and they are tight with no play. SO I figured it was the shaft.

My local driveline guy went to balance the shaft and it was slightly off. Had the shaft cut, rewelded and fixed. Balances out beautifully on the machine. I put it back in, grease up everything and bam, vibes are back.

Any ideas why????

Click to expand...

Are you sure the ujoints are perfectly centered in the yoke? I was having the same issue with brand new TW shaft post-lift. It turns out my yoke is slightly sprung, allowing the ujoint straps to be tightened while still slightly off-center. Vibes started out around 45 or so and became very bad at anything over 60.

RCP Phx said:

Whats your pinion angle?

Click to expand...

X2

I just lifted my MJ about 6", with longer LCA's but didn't have the UCA's so I kept the stock ones in temporarily. Had bad vibes, and had to pull the front DS for now until I get longer UCA's and get the pinion angle (and caster) back.

Jeff

x3 on the pinion angle. I had similar problems, I didnt cure mine yet but after doing some research and angle finding, with stock uppers its just not allowing my front axle to be at the right angle for the driveshaft. I'd check out the angle and possibly get some adjustable UCA's

Ujoints look centered in the yoke, Ive taken these shafts out plenty of times. I'd imagine I would have noticed.

Im am gonna try the front driveshaft out of my fathers 01xj just to see if it makes a difference. Also check to see that either of the yokes aren't cracked or distorted.

Normally I know how to measure pinion angles but on a double cardan joint, what part of the double joint do I take my measurement from.

Ive been looking at either bds or re upper and lower arms as an upgrade in the spring time. But I looking at fixed arms as I don't plan to ever be higher than 4" on this rig.

Let us know what you find--my DS was misaligned just the slightest amount--def not something you could see visibly.

Problem fixed. The centering kit I used was no good. Now the drivetrain is smooth as can be.

What do you mean by centering kit? for the driveshaft?

Correct, the centering kit. The actual ball that centers the double cardan joint. The kit is usual a new ball and seal. The seal on my was damaged, allowing water in there. That wore out the grease and the ball cooked itself.

Death wobble with 3" kit.... Not a problem. I spent a month tracking down every conceiveable issue and finally found out that it is an easy fix.

Ok from the Jeep manual... Loosen all your adjustable stuff (track bar especially!)

Make sure you have everything connected! Sway bars and stuff! <<-- you would be amazed how much the sway bar affects this!

Ok, pretty much jump on your bumer a few times to get it moving up and down..
Now push it from the side a few times to move the front end enough (at least 6 to 8 inches)

This will center your front end! The jeep system is self centering, which is the main cause for the wobble. As you drive the "system" is trying to correct itself.

Now that you have done all this tighten everything down to factory Specs!

I have a 3" kit with a rusty's adj trac-bar, if you need me to measure the length of mine to make sure yours is set to the right length I will, let me know. Ensure your rubber is good on the sway bar links and those are conected to spec. I have 3" spacers to drop the sway system down to where it is supposed to be. I also have the drop pitman arm for the 6" kit.

I no longer have any wobble after I did all that and routinely drive my XJ over 70Mph on the highway.

Be very meticulous and pay attention to detail when tightening everything! it is so critical on the Jeep set-up. Being off a little bit will give you wobble.

This also fixed vibration problems also, since the axel system is no longer moving around from side to side.