Axle U-joint 96 ZJ 4WD

[ken729]

Have some rotational play on the front axle u-joints. Specifically when I jack up a front wheel and turn the tire by hand there is some free play before the axle is engaged. I've read that this may be normal in order to absorb sudden engine torque but I'm not finding too much info on the topic. Any ideas or info ?

[JDPascal]

Originally Posted by ken729

Have some rotational play on the front axle u-joints. Specifically when I jack up a front wheel and turn the tire by hand there is some free play before the axle is engaged. I've read that this may be normal in order to absorb sudden engine torque but I'm not finding too much info on the topic. Any ideas or info ?

Unless you are putting your hand on the axle joint and feeling the play in the CV joint that way, it is normal to have some free play in the axle/diff when you turn one wheel like you describe. There is backlash in the ring and pinion and in the differential side & pinion gears and a little in the axle splines, that allow the axle/wheel to rotate. When both wheels are on the ground, only the ring/pinion backlash and the little in the axle splines is affecting things. The side/pinion gear play in the diff cage is felt mainly when there is a difference in wheel speed from side to side.

I have never heard the "asorbe sudden engine torque" explanation given. In fact, as the free play is taken up, extra free play only serves to increase the shock loading on the parts.

There can be extra free play in the diff if the wheels were spun when stuck and the shaft for the diff pinions in the cage becomes worn. A new shaft and diff pinions will usually fix that tho.

So long as there is no free play inthe ujoint and the diff is in good shape, you should be ok

JD

[ken729]

Thanks fot the info on that. I think what I am experiencing is free play in the u-joint itself. When I jack up a front wheel, I can rotate the tire about an inch before the axle starts turning. This is happening on both front wheels. There is no noise or any vibration coming from the front end. Should I be looking at replacement?

[JDPascal]

I think that you probably have CV joints in the axles. They have rubber boots covering the joint. If the boot is not torn and grease thrown out, the joint is usually good.

The other symptom of a worn CV joint is popping and clicking when you are turning.

I guess it might be possible that the joint is worn but I highly doubt it (if the CV boot is good).

A little bit of play in the diff will translate into a lot of movement at the circumference of the tire.

JD

[ken729]

I took another look at the wheel a short time ago and I dont see any rubber boot or anything that looks like a CV type joint. There is only an axle end u-joint on each side. That's where the rotational play I mentioned is happening when I turn the wheel by hand. I get about one inch of rotational free play ( measured at the outer edge of the tire ) before the axle starts to turn.

[JDPascal]

I don't think it is that usual for the JGC's to have standard ujoints on the front axles. They are stronger but not as smooth running during turns.

When you have the front wheel jacked up and supported on an axle stand, have someone else rock the tire back and forth while you put your hand on the ujoint to feel for play between the inner axle and the outer stub shaft. OR-maybe you can see the play in the joint happening.

A standard u-joint is more likely to go bad at this location than a CV joint were the boot and grease is still intact.

I know too, that my 96 ZJ has a similar amount of play at the tire with good CV joints and normal diff backlash & play.

JD

[ken729]

Thanks for all the info. I guess I can't really explain why it is that there are u joints at the axle ends and not CV joints in this vehicle. As far as rocking the tires, everthing is real solid. There is no movement of anything regardless of where I grab the tire. Only when I spin the tire do I get that inch of free play before the axle engages. Thanks again for all of your input.

[dksob81]

I have seen a few ZJ's with U Joints instead of CV joints. If when you spin the tire you can see the free play int eh u joint then it is bad, I would pull the axleshaft out and check it (this would be the easiest way to check for sure).

NOTE: There will be a little bit of play between the wheel and the driveshaft. If you spin the wheel and it has a lil bit of play before the driveshaft starts spining <---- this is normal.

[ken729]

Yes- it's that little bit of free play in the spin that I was concerned about. Glad to hear its normal - spoke with two dealers this afternoon who said same thing. Thanks!