TH400 Question

Can anyone save me from having to crawl under my rod in the snow and tell me what the thread size is for the TH400 trans fluid pipes. Thanks

 

same as a 350

 

the oil cooler lines have a male 5/16" inverted flare , they screw into an adapter that has a female 5/16 inverted flare. the other end of these adapters is 1/4" NPT and screws into the aluminum case

 

Thanks guys i'll get both from a buddy in the trade and let y'know how it all pans out.

 

Pretty sure that at least some TH400 had 3/8" cooler lines. Cadillac maybe?
I'll bet Squirrel knows.

 

well , i have messed with a couple th400s and i thought they had 5/16 lines , but it has been a while and maybe i'm wrong? who knows for sure?

 

Looks like you might be crawling under it. I have 4 TH400's here. The Pontiac
and Chevy are both 5/16" cooler lines.Both Cadillac TH400's I have are 3/8",
so I guess the answer is they used both depending on the application.

 

5/16 lines

 

No.

 

Later TH350's and TH-400's had 1/4" female pipe threads in the case that the line adapters thread into. The earlier cases have a straight thread (not sure of the size) and use a copper washer for sealing. Be careful if you have the pipe thread case...if you tighten the adapters too much and hear a snap/click, you just cracked the transmission case.
Once cracked, the resulting fluid leak is a pain in the butt to fix.