727 Slipping out of 3rd

[Swampwing2]

I looked back about 15 pages and did not see any similar posts, if there are any I would appreciate a link.

I am finally getting around to dealing with the vertibird again. Engine is a cast crank, mild cam, about 10:1 compression, 440. Transmission is a 727 out of a mid 70s truck but I really have no idea beyond that. I "rebuilt" the trans, (first time ever) about 10 years ago. Basically replaced the clutch discs, seals and basic kit parts. I did not replace the bands, drum or any hard parts.

I was on a two lane highway, about 100 miles into a 140 mile trip. Car was running great, cold AC and everything. I went to pass a slower car going about 50. I put my foot down, the transmission downshifted and accelerated nicely. About mid way passing the car, I hear a weird clunking, like something metal falling off and a large puff of blue smoke pouring out the back of the car. The transmission shifted normally and the car still pulled strong. I could not immediately pull over because it was such a tight stretch of road. The smoke cleared about 20 seconds later and the car was running normally. When I finally pulled over, the fluid was red, clean and full. The kickdown linkage was still there and functional (top and bottom). No unusual noises or smoke was evident. I started driving it again and it was fine for about 10 minutes at highway speed 60-65. Then it seemed to pop out of 3rd gear as the engine revved up and the car slowed down. Lightly backing off the throttle cured it. Then it kept repeating every few minutes, until I decided to park it and tow it home to prevent doing any real damage to it (Hopefully).

What is the most likely cause of it slipping out of 3rd, and can it be fixed while still in the car? How do I check it?

If I need to rebuild it, is the TF1 kit worth doing for a street car? I saw several posts about the TF2 shift kit. I don't race this so I don't need a bang shift every time by any means. I just want it reliable and firm. I also saw a post about the correct way to drill the valve plate, which may be different from the directions. If needed, I will probably have a shop do the rebuild this time, but want to tell them the way I want it to work.  Any other must do upgrades I should have done while it it out?

[Stegs]

i dont know about a rebuild

but for a kit get the TF2

it came highly suggested to me by more than a few people and i love it


Go that way!

[John_Kunkel]

What is the most likely cause of it slipping out of 3rd, and can it be fixed while still in the car? How do I check it?

Does it slip out of third and shift down to 2nd or does it just slip out to what seems like Neutral? If the latter, the problem is probably worn seals/sealing rings in the front clutch. Time for overhaul.

[Swampwing2]

It does not go to second, it clearly goes to neutral. Didn't want to pull it if it was something like a band adjustment, but that did not seem likely based on other posts.

Will probably go with the TF2 kit unless others chime in about the TF1.

Thanks to both of you for the input.