Automatic gurus - 904 build

[Meep-Meep]

Hey there, it's been about 35 years since I been into one of these (mostly 4 speeds lately) and I'd like some input on what may be going on here. Pretty sure I have all the parts installed and correctly but I have a lot of input shaft end play. Like a shitload. Tail shaft is in and tight with gasket and the rear ball bearing is seated in the snap ring. The gear train has the desired clearance after adding about .030" shim behind one of the thrust washers.

With the tranny on it's side I can push the input all the way in until it stops then pull it out until it stops but the movement is damn near 1/4" as if I left out one of the fiber washers, which I did not. I did get a 4 clutch drum and low gear set from A&A and all that seemed to be fine but I did not compare the difference to the old stuff. Also keep in mind this is an original 69 tranny that looks like it's never been apart and was working fine. Yeah, yeah, if it works don't fix it.... But it's good I pulled it apart because the high gear clutch pack was badly worn and the piston seals have taken a set. Looking at FSM diagrams I can't imagine I left something out and want to know how I can end up with damn near 1/4" of end play when the FSM says up to about .080".

Here are pics of the input shaft all the way in and all the way out. Note in the "all the way in" pic you can't see the rear clutch assembly but in the "all the way out" pic you can see the edge of it peeking through the slots in the drive shell. I'd love to get my leaning tower of power Dart back up and running but it's fighting me every step of the way. Might be a sign that it needs a hemi.

 

[dvw]

The only thing that control overall end play (if the rear is locked in correctly) is the #1,2,3 thrust washers. The low gear set and drum are new. The gear train clearance is correct so the low gear set is not the issue. If the drum was thinner (overall front to back) for some reason that would do it.
Doug

 

[Meep-Meep]

The only thing that control overall end play (if the rear is locked in correctly) is the #1,2,3 thrust washers. The low gear set and drum are new. The gear train clearance is correct so the low gear set is not the issue. If the drum was thinner (overall front to back) for some reason that would do it.
Doug

Thanks for confirming. I was thinking about this and it's very possible I have that rear ball bearing on backwards. The snap ring groove is offset and suspiciously about the amount of my end play. I will check tomorrow and hope to find the smoking gun and report back.

 

[Meep-Meep]

The bearing was installed correctly so I dug deeper and found the 4 clutch drum I got had one thrust surface .050" lower than the original. I do not have an explanation for that but after measuring and determining the .050" was on the pump side I used an extra planetary thrust washer as a shim behind the fiber washer. All I did was open the ID to 2.065" and sand down the three tangs so they cleared the drum. Final end play is .060" - right in the middle of the tolerance. Now after all this I hope it works.

 

[oldkimmer]

Lots of times when u change a drum the clearance changes. Good luck 2 ya. Kim

 

[wyrmrider]

ingenious must have been a rebuilt part?

 

[Meep-Meep]

Here is the final outcome. The drum was the culprit. .050" shorter on the one side for some reason. You can see the difference of the gap under the parallel as well as the fix. Thanks to Doug making me look harder at the drum stack.