Clunk when shifting from fwd to rev.

[J20DAN]

My '79 J20 has developed a clunk when shifting to reverse and a clunk/ping when shifting to forward. I am guessing the rear is probably out of whack on pinon ring gear alignment but I thought it might be something else in the driveline. It does not make any bearing noise or other on the highway. It has auto/quadratrack. It only has 41K miles but was used as a plow truck earlier in its life so it probably got a quick shift back and forth. Anybody had a similar problem?

[Stuka]

check your u-joints for play. then put the tranny in neutral and see how much the drive shaft turns lock to lock.

[Will Morris]

Check the chain in the Q-trac for slack. I just replaced a Q-trac chain in my Step Dad's Jeep and it made a huge difference.

Will

[TexasJ10]

When you check the rear ujoints, lift the back wheels off the pavement. You may not be able to move the ujoint if you don't.

[Crazy_Jeepman]

Most likely Culprit if all the above show no signs of failure, would be the Trans output shaft. The corse splines wear and creat slop between the output of the trans and the input of the T-Case. Very common. ;)

[Max Power]

Broken or loose engine mount/tranny mounts can make a klunk in the driveline

Robert

[Da Big Blue]

Possibly rear pinion bearing?

[imported_Big Red]

Mine was a worn out QT chain. ARGH!!

[Zacko]

Could be a bad slip joint too. Put it on a rack and have someone put it back and forth from drive to rev while you stand under it and look. You should be able to see where the slop is.

[D.A. Davis]

Pull your rearend inspection cover and check for wear between you spider (pinion)gears and the pin. Also, the pin and the carrier. This is very common in all vehicles. You can watch them move by turning the driveshaft by hand.

[illegalFSJ]

I had similar symptoms on a '79 wagoneer. Turned out to be the front axle U-joints.
Good luck!

[SAustinwag]

xfer case i'd bet. Shaft thingy is all used up.