transmission output shaft play

When do you hear the clunk? Is it during shifting? If this is the case and all you have is a clunk then I would not do anything to address it because it is probably characteristic. I attached a TSB that talks about this.

Long story short when the torque is removed from the output shaft during a shift the output shaft clashes on the splines in the other direction. They call it torque reversal. I think you are okay if all you have is a clunk during shifting. Let me know if you have questions. Thanks

Thank you for your answer Kasekenny1. I have been trying to trace a single bang or a thud on take off only and only when taking off aggressively when I checked driveshaft (truck not running). I see movement in the yolk and hear a clunk when I push up or pull down on it with my hands. Is this normal? When driving other than that thud on take off only there are no unusual noises or clunks. The yolk is greased. I checked front suspension ball joints and steering and all seems tight. Also engine mounts. It will not bang in reverse. But I do feel the thud/bang through the front of the truck. Thanks.

Okay. If it is on take off with aggressive acceleration, that is most likely your issue. Clearly without feeling it, I can't tell you if it is normal. However, keep in mind, that what you are feeling is the slack being taken out of the drive-train. The question is, is that too much. The only way to know that is to measure output shaft end play but that is done when rebuilding the unit. There is no spec on output yoke end play which is what you are seeing.

The only way I have had success with checking this is comparing it to another unit that does not have the same noise. Clearly that is not helpful in this case.

I attached another TSB that talks about single clunks on acceleration and then throttle release. Basically this is called gear clash and it is normal.

If your clunk is excessive then the only option is to go through the drive-train and reduce the tolerance between each of these transitions. That means from input shaft, output shaft/yoke, u-joints, and then the pinion and backlash.

Unfortunately there is no one thing that can cause what you are seeing and a 1/16th of an inch movement on the yoke does not sound excessive to me.

Does this do it on "normal" acceleration or does it have to be aggressive?

Only on aggressive acceleration from complete stop. Will not do it if I get the truck moving slowly for a few feet and then accelerate fast. It is more of a bang or bump then a clunk. What I feel and see in the yolk (truck not running) is up and down and side to side movement between the yolk and extension housing bushing that causes the bang, not output shaft end play movement. I can make it bang by using my hands. Thank you.

Clearly I am not hearing this noise with you but what you are describing sounds like the slack in the drive-train is being taken out when you accelerate and causing the noise. This is what is called gear clash and there is not much you can do about it. When you are moving the lash is removed and doesn't make the noise. Again, the play that you are seeing does not sound excessive. Have you removed the driveshaft and inspected the output splines to see they are worn?

The splines are not worn. I may have to live with this. Thanks for all your help.

Unfortunately I think you are right. While it may be abnormal weighing the exploratory repairing that will have to do it doesn't seem to make sense.

Sorry we couldn't resolve it.