Clunk when shifting between reverse and drive

[shotty]

My 1028 has started clunking pretty bad whenever I shift from park to drive or drive to reverse. It doesn't clunk when I let off the gas and coast. I put the truck in neutral, set the parking brake, and crawled underneath to see if it was the u-joints but those all look fine. If I grab the rear driveshaft and rotate it, I can turn it about 20 degrees. I've included pictures where you can see that one end of the u-joints is facing directly downward and after rotating it counterclockwise it has turned up just a bit and you can now see the bottom of it.
Is this too much play in the rear end gears? Is it normal for these trucks to clunk even with good ujoints?

 

[Bunkerbuilder]

Keep in mind its not just the u joints that could be the issue but the slop in the driveline could also be the spider gears in the differential.

But the driveline is the path of least expence and also the easier way to figure it out, or at least rule out that the driveline is ok and that either was the problem or the problem lies elsewhere.

with the removal of 4 bolts you can pull the shaft and figure out if its the u joints or an issue in the differential.

When you have the yoke in your hand and your turning it keep in mind that there is more than just the backlash between the ring and pinion that you are fèeling and hearing.

 

[cucvrus]

These rears do have a lot of lash to them. I put a new 14 bolt military rear in a stick shift truck and it had a lot of back lash between gears asnd when going in reverse. I never took notice to it in a CUCV but I did in the stick shift 2WD truck I put the rear in. Check it all out. Bunkerbuilder may be on to something.

 

[TGP (IL)]

You can check your differential if it makes you feel better,and do make sure your U-joints are
Not going bad.
But I will tell you that the No-Spin equipped differential has a lot of back lash to it.
It's in the locker itself and not the ring and pinion.
The 20deg of movement your seeing is pretty normal.
Tom

 

[shotty]

These rears do have a lot of lash to them. I put a new 14 bolt military rear in a stick shift truck and it had a lot of back lash between gears asnd when going in reverse. I never took notice to it in a CUCV but I did in the stick shift 2WD truck I put the rear in. Check it all out. Bunkerbuilder may be on to something.

You can check your differential if it makes you feel better,and do make sure your U-joints are
Not going bad.
But I will tell you that the No-Spin equipped differential has a lot of back lash to it.
It's in the locker itself and not the ring and pinion.
The 20deg of movement your seeing is pretty normal.
Tom

Good to know, that makes me feel a lot better since I don't have my tools yet so I can't do anything about it. I'm still going to open up both diffs but I'm not terribly worried anymore. Thank you.

 

[DeucesWild11]

I had the exact same symptoms with the deuce but no real difference in drive shafts, my issue was the u joints.. I'd check them again. Visually it's not that easy to spot without turning it hard and then back again. Here is my post, I put together some videos on the sound, perhaps you are hearing the same thing or something different?

http://www.steelsoldiers.com/showthread.php?125940-Driveshaft-Clanking-Sound&highlight=

Good luck

 

[barefootin]

To add to others, the 14 bolt rears do have a lot of play. If the U-Joints and Yokes check out, another thing to check are your rear brakes. If they aren't bled properly, have weeping wheel cylinders/lines, or a weak circuit in the master cylinder the "normal" play can result in a louder clunk due to more drivetrain movement when shifting from D to R. I experienced this on my 77 and on my 90 Civy with a 14 bolt when the rear brakes were not holding properly.

 

[rchalmers3]

I realize you are focusing on the driveshaft deflection, but may I suggest confirming the motor and transmission mounts are ok.

Rick

 

[scottladdy]

The locker in the rear diff has play. It is the design of the locker. Does not hurt to pull the cover and check things out however.