I fixed the leak today! It was the rear (return line) 90 degree fitting. I forgot to put an o-ring inside the female side where the line screws in. For extra precaution I wrapped some high density industrial grade thread tape around the threads of both the line nut threads and the male fitting threads to stop any leaks. All sealed up now and working well!

Now I'm afraid that the condenser might have been a step to far in this project, as it may be blocking flow some due to it's small internal passages. I may be swapping out the condenser for a F-250 oil cooler in the near future, we will see. I need to call around to some tranny shops and get their advise on the topic.

Hows the balance on the driveline? Any vibrations?

i am reading it too! & i think you've taken a lot of the mystery out of the task of working on & maintaining automatic transmissions

Well then it sounds like its time to check that driveshaft. The tires are new as of the 20th. Balanced and all!

I was wondering about the U-Joints, myself, not entirely sure that was the case though.

I have rebuilt the transmission, swapped out the rear axle for one that is known to be vibration free (was in my 78 sedan, originally came from a 73 wagon as well though), new U-Joints, new transmission and motor mounts, and new tires with freshly balanced rims.

The only thing I have not have professionally tested yet, is the drive shaft. If that's not it, I don't know....

I have a shop who will spin balance my drive shaft for $70.00. Isn't that a bit expensive though?

  If seal still leaks check the slip yoke make sure its not worn and also check the spring on the seal  are know to pop off when installing seal. One trick to void come backs is to pack seal with petroleum jelly and put into freezer for 20mins then install.Also you can tighten the spring alittle if your slip yoke is worn by turning spring apart and cut 4 coils off the female end and turn male end back in and reinstall. I hope this helps you.

So for the past two months I have been working off and on rebuilding the transmission that Walt gave me but failed shortly after. I believe I found the culprit to it all as well. It seems there there was negative end play and everything was mashed together. It is surprising it lasted as long as it did! When I pulled apart the clutch packs there was absolutely NO lining left on the clutches for the direct drum, but the rear drum seemed to be just fine.

Also, the LEAST noticeable damage was the sun shell. It seems that the negative end play forced the end of the sun shell inwards, making the end of it concave instead of flat. I spent an hour an a half trying to figure out why I couldn't get the sun shell tabs to lock into the direct drum tabs.

I managed to locate a good sun shell locally and here is the difference pictures:

Pic 1) You can see the bowl type warping in the old shell's base in this picture

Pic 2) You can see where the forward planetary gear set was actually making contact with the inside of the sun shell. That's a lot of force required to bend the shell in that much!

pic 3) Here you can see how much the sun shell's bushing wear plate was bent due to the negative end play.

pic 4) And here is the difference in the plates when removed from the sun shells.

Dave, I'm impressed. I know you must of mentioned it somewhere in all the detailed instructions that you provided. How do you change the shift seal? My C4 is leaking around the shift linkage going inti the side of the trans.