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Replacing the trans cooling lines, I’m worried about the fittings leaking (harder to get to once engine back on the frame). Does anyone know if I should put some stuff on the threads to prevent a leak?
They should be inverted flares. In which case a leak isn't going to occur at the threads, so teflon tape won't do any good. Here's a good thread on '67 trans/cooler lines. Good luck.
Replacing the trans cooling lines, I’m worried about the fittings leaking (harder to get to once engine back on the frame). Does anyone know if I should put some stuff on the threads to prevent a leak?
The fittings that screw directly into the trans case are NPT threads and should have sealant (teflon tape or liquid) before being threaded in. The fittings on the pipes are inverted flare and do not need or want any sealant. The threads on inverted flare are not the seal, it's the metal-to-metal conical flare that makes the seal. Note that if you don't hold the fitting in the trans case while you are tightening the inverted flare nut, you can disturb the NPT thread seal in the case, causing a leak there. Always use two wrenches to loosen or tighten these fittings. Yeah, that's a lot easier said than done with the trans in the car.
EDIT: I just noticed that the fittings that screw into the case have sealing washers on them. These may be straight thread fittings that seal with a washer, not NPT. I know that later GM automatics use NPT there. Be sure you look at them carefully.
I’m almost positive the 350/400 transmissions all used cooler line fittings with sealing washers. The Powerglide (and probably the Jetaway) used pipe thread fittings.
It’s very easy (and pretty common) to crack the case trying to use taper pipe thread fittings on the 350/400 cases. I have one of each case in my collection that I need to get welded.
Sorry guys. I think Joe & Matt are correct. With a picture staring directly into my face you'd think I might have seen the sealing washers. For some reason I was thinking of the oil radiator cooler end line fittings which I thought were inverted flare.
Gleaming the web I found this (H.A.M.B.) from a person who had this to say about that but unclear if this applies to all TH350.
Make sure that you use the correct fittings, with either inverted flare, barb or compression fitting. 1/4 NPS with parallel thread and washer for inverted flare and double flared hard line with tube nut (1/2 20 for 5/16 tube or 7/16 24 for 1/4 tube). NOT NPT tapered thread which will crack your case.
I’m almost positive the 350/400 transmissions all used cooler line fittings with sealing washers. The Powerglide (and probably the Jetaway) used pipe thread fittings.
It’s very easy (and pretty common) to crack the case trying to use taper pipe thread fittings on the 350/400 cases. I have one of each case in my collection that I need to get welded.
Good point. I'm in the middle of a 200-4R right now, which is why I was thinking of the NPT threads.
The old lines came off real easy, new lines in (yes they were flared ends, a lot less thread engagement then I would have thought).
Those allowed the engine and trans to finally go home after being out for over 17 months.
