Hi Matt, Dave here. We've met in person once or twice. I'm facing a similar problem. Not a pagoda, but similiar transmission on a '72 w114. Swapped out the transmission with one from a w108. Drove it around for a day before it started slipping again. Since I kept the same FC, I'm thinking it may be the problem. Going to pull it back out and have a look. I've never had ATF leaking out of the FC though. I've tried to contact the transmission guy in Sunland, CA and also have been talking to one in NJ. Hoping I don't have to get the whole transmission rebuilt.
Is there any way to check the FC from the outside, without pulling it out? Also how would I check the pump pressure.
Dave
'72 250C