4T65E End Play question?

[Mikegee52]

Hello all,
I have been reading your forum for some time but I finally registered and have a question. I am working on a 4T65E trans. I'm thinking how to best word this to make it clear.

It seems to me that the endplay of the final drive is completely seperate from the endplay of the trans. (trans is less than .006 Final drive is .005 to .0025) I have a question and a possible answer. (guess) My service manual shows special tools to "push" the final drive forward then check the trans end play. The only thing I can think they are doing is making sure the final drive ring gear is pushed tight against the snap ring that retains it in the housing. None of the thrust from pushing on the final drive could be transmitted through the sun shaft and gears etc? They just want to be sure that when / if the final drive ring gear would ever move forward it won't run out of transmission end play.

I hope that is clear enough that you can understand my question. It's the best I can do right now. I am replacing the final drive and rebuilding the trans so I need to understand this as it is a little confusing why else they would push the final drive forward before checking trans end play. It seem the only thing that could move and affect the trans might be the final drive ring gear.

I'm posting here because it seems there are some very knowledgeable people that might help. So I say thanks to all in advance.
Mike

[Trannyman95]

The final drive endplay is seperate from the overall unit endplay. When setting the main endplay via shim under the bearing on the input clutch drum you need to push the differential towards the transmission to take all of the slack or endplay out of that section. The easiest way to do this without the preload tool showed in the instructions is by having the final drive/differential and tail housing already set up and installed and the transmission standing on this end so the main line of the transmission points straight up and down. Then you can use a flat blade screwdriver or small prybar to pry upwards on the final drive by inserting it through the speed sensor hole in the tail housing. While prying up on the final drive you will check the main line endplay which without the special tool to measure this you will lay a straight edge across the case and use a feeler gauge to measure the difference from the case edge to the top surface of the driven sprocket support and adjust accordingly.

[Mikegee52]

Trannyman,

You're the best! I figured as much but still have one question if only for my own curiosity. What pushes anything up in the main? It would have to be either the sun shaft or the final drive ring gear being pushed against the big snap ring, wouldn't it? It seems those are the only 2 that would affect endplay in the main and I doubt it is the sun gear shaft. (I could be wrong) Does the sun gear shaft only float in the line so the sun gears can find there own center where they are happy?

I have the input yoke off an old axle that I put in the final drive. Then I stand it on that yoke and block up the trans so it stands on the yoke. (therefore pushes all up)

Thanks again for your expert help,
Mike

[Mikegee52]

Trannyman,
I just want to say thanks again. I understand everything you explained. It is so much easier when equipped with some knowledge. You did an excellent job of describing things. I am a diesel mechanic and have experience with lots of Alison transmission. These are similar but very different.
Mike

[Trannyman95]

Glad I could help out. The sun gear shaft does push up on the geartrain inside the trans which is why you need to push the final drive inwards to compensate for its endplay. If you just push up on the shaft without the final drive in place it can push in further and give an incorrect reading, that is why the tech manual shows having the final drive end play set first and already assembled.