Looking for a knowledgeable tech that might know, right off the top of his head, which of the two lines coming out of the R/H side of the TH400 transmission, is the 'return' line. One is the supply to the cooling portion of the radiator, the other is the return line back to the tranny??
Thanks in advance for your time and help.

 

Teesquare. Interesting question. I replaced mine after having an engine bay fire due to one rupturing at the back of the engine and spraying t-fluid on the exhaust. I can't remember which one is to or from. I also don't see what difference it would make. Explain your concern, if you would. I replaced mine with high pressure hydraulic rubber hose and ran them down the right side of the engine bay. Much easier than putting them in the original position behind the exhaust manifold. Gets the lines away from exhaust heat and is less expensive.
Cheers, RagJag

 

Turn car on. Put in drive. Wait 10-30 seconds. Put car in park and turn off.

Feel lines. coolest line is the return line.

Anyways, I *think* the return is the top on a TH400

 

Sidescrollin -
Thanks - pretty nifty idea!! Have you done this?? I'll let you know.

Teesquare

 

RagJag -
Well, the reasoning for the question is not totally revolutionary - but very 'detail oriented'. I was taught by an elderly mechanic, late in my gas-station mechanic years after coming out of the Marines and working to go to school - that the very best way to perform a 'Top Notch' transmission service - was NOT to just drain and clean the pan, change the screen/filter and add the required amount of new Dextron - but to open up that return line and then as the trans front pump (engine running) pushes ALL the fluid out of the torque converter and cooler in the radiator - you have flushed the entire system. After that it never made any sense to me to jut add some fresh fluid to the existing old fluid. So - I've been doing that for the past 50+ years. Except on the Jag - you can barely SEE the lines to disconnect or interrupt them to perform this flush. It just so happens I had to drop the exhaust to replace the spring, bushing and rubber seat of the center trans mount - and I can now get at the lines to put a compression fitting in the line to drain the fluid.
Sorry for the long winded answer - now you know the story!
Thanks again!!

Teesuare

 

OK....found the answer.....Sidescrolin was 100% correct!! The top line on the R/H side of the TH400 is the return line from the cooler in the radiator. I found an old 1960's era Hot Rod book on the 400 and after enough page turning...found the magic two sentences.
Thanks again!