How much play in a driveshaft Ujoint is too much?

[TedW]

The splines are tight but one of the rear ujoints has a bit of play. I have a set of new Ujoints but haven't installed them yet - may not get to it for awhile.

[jp-]

I've seen people keep running them until they just fall out. When my first (and only) U-joint failure in the 109" happened, a cap completely fell out. I had to drive it home with a "bang" after each shift. Realistically they will keep going for a long time even when well worn. If you have 1/8" to 1/4" of side to side, you need to change them. But, you will probably notice a bad vibration before they get to that point. Definitely change them if you get a bad vibe.

[daveb]

hi

there should be no perceptible play. running them until they fall out as described can kill the driveshaft.

The splines are tight but one of the rear ujoints has a bit of play. I have a set of new Ujoints but haven't installed them yet - may not get to it for awhile.

[jp-]

Dave,

I didn't say it was a good idea, just that I've seen it done . No there shouldn't be any play, but if there is less than 1/8" it probably isn't going to blow up in the time that he can find to change it out.

[I Leak Oil]

When U-joints go bad they can cause damage to the yokes and slip splines on the shaft and even put undue stress on the diff pinion bearings and transfer case bearings. If it lets go while your driving it'll cause all sorts of damage not to mention you'll need to burn your shorts afterwards! They are cheap and easy to change. If there is any play just change them and save yourself the grief.
Jason T.