Ujoint failure

Aside from the Jeep suddenly feeling like I'm driving on a railroad track, what is the best way to determine if I have a bad u-joint and which ujoint it is? I have a Tom Woods SYE and suspect that its the joint at the pinion. I just haven't had the opportunity to get under there yet. There are plenty of articles about replacement but none about testing that I could find,.... unless of course your drive shaft is on the ground.

Set the park brake. Chock the wheels. Put trans in N. Crawl under there and start wiggling driveshafts.

cruiser54 said:

Set the park brake. Chock the wheels. Put trans in N. Crawl under there and start wiggling driveshafts.

Click to expand...

Thanks! Easy enough. Sometimes the obvious escapes me.

Word of advice. If you find that one of your u-joints is TU. Replace both of them and check your driveline angle and pinion angle.

Did you shim up your rear end when you lifted your XJ? Even at 3" of lift your pinion angle changes considerably. Usually the rear pinion u-joint goes first on lifted rigs with bad pinion angles. Becasue of the angle being different at the front yoke in realation to the rear pinion, when the drive shaft turns, the two u-joints are our of sync with each other, this causes a vibration at the pinion u-joint. In some cases it can also wear the pinion bearing and seal on the rearend.

If you have a slight vibration at low speeds, try a 2.5 - 3 deg shim under your leaf springs. For a moderate vibration, try a 3-4 deg. My rig is lifed 4" and had to use a 3 deg shim.

Don't be fooled by your tires. If you feel even the slightest buzz or vibration in the sterring wheel, it's may not be your tires buzzing on the road surface or alignement?

When you lift a solid axle rig, unless you have adjustable lower control arms, your caster angle is actually to far negative towards the front. This also sets the pinion angle on the front axle. As you know in part time 4wd, the front drive line is always turning. So that buzz in the sterring wheel when your rig is in 2wd could be the front caster angle working against you. If the buzz gets worse in 4wd then you deffinately need to change your caster angle closer to factory spec angle of 2 deg.

That can only be done if you have adjustable lower control arms. After market control arms are made to stock factory lenghths. So at 3" of lift, if you used your stock control arms or tubed after market ones, your front caster is now from 5 -7 degs. Does not seem like much of a change but it is alot. This will also stress the front pinion u-joint as well and sooner or later you will be changing that one out too.

Probably more information then wanted to know. Hope this helps :eeks1: