Trying to replace the cooling lines on my C6 transmission and am running into some difficulty. The adapter fitting that goes into the transmission on the outlet is cracked. I need to replace it in order to replace the lines. From what I'm seeing the fitting is 1/4 MPT with a 5/16 inverted female flare on the receiving end. Is that correct? I've also noticed there are different style adapter fittings that have male ends to go onto the lines. Dies any have any advice on which adapter fittings would be best to replace the originals as I think I'm going to just replace both. Also does anyone know whether or not these fittings can just be unscrewed from the transmission case with out screwing up anything inside the transmission. Thanks

 

A well stocked hardware store should have the right fittings. When I needed new for the radiator end of the trans cooler lines "Ace was the place".

 

I "believe" you have the correct size (1/4" MPT X 5/16" inverted flare). I'm away from home right now and can't check mine. But you can just unscrew the old fittings without problems.

 

...and in case you wanted to remove them entirely, the threads into the trans itself are 1/8npt.

I redo mine with 1/8 by -4 AN and run hose. Makes it easier for me to route the cooler lines wherever.

 

Look like I was wrong. Wasn't sure about the 1/4.

 

It's ok Mike, I have two 1/4inch by -4 fitting hanging on the wall because I once made the exact same mistake :P

 

Lower picture.

Both fittings on the trans are the same: 87944-S8 .. Fitting ~ 1/2" -20 x 5/16" tube.

PREAUS MOTOR CO. in Farmerville LA has 22 = 318-368-3805.

GREEN SALES CO. in Cincinnati OH has 833 = 800-543-4959.

 

So the stock fittings that came out of my c6 were1/8 npt male to 5/16 inverted flare female. I replaced those. Both were cracked and one was leaking bad with tge other soon to follow I'm sure. After much deliberation I ran braided stainless hoses and used AN fitting in the transmission and radiator with matching AN female ends on the hoses I made. Thanks for all the advice.

 

That is the same setup I run. It works very well and makes it easy to remove the trans/trans cooler/radiator.
Even better I can often leave things hooked up and just swing it out of the way.

Good job!
Drew

 

Im digging this thread up trying to figure out the size thread of the inlet and outlet cooler fittings on my C6, mind you its a 1968 and it looks like these fittings changed over the years ? I keep reading that the case input thread is 1/8npt, but thats not what I have here, it measures .50,.51,.49 depending on where you measure on the threads ? The flare fitting size is the 1/2-20. Im trying to go straight AN hose but cant figure out this size, its not a 1/2-20 or 1/2-13. I can get a M14-1.50 to thread on easily but its slightly to big as a 'bolt' fitting into the case... Any help is appreciated.


C6 Fitting

 

I think Ive answered my own question, if anyone else is trying to find the original case fitting size to a 60's C-6, im 98% sure its a 1/2"-18 UN/UNF thread .... and good luck finding any AN adapter fittings for that size, looks like I will just go into the fitting itself with the 1/2"-20 to AN6... Just didn't want an additional fitting to give me an additional leak someday...

 

Digging up this old thread but if someone else is looking for this fitting, I think you should know it is NOT 1/2-20 although it LOOKS like it is...it is super close.

I ran -AN6 to a filter, radiator, cooler, and back to transmission. The correct fitting is https://www.redhorseperformance.com/...ng-black-2pcs/

1/4 NPSM.

I originally sourced 1/8" because of several threads stated it was 1/8. Mine was definitely not 1/8. So I pulled it out and it looks just like a 1/2-20 oil drain plug thread, but when you try threading the old fitting into a 1/2-20 nut, it won't go at all.

Hopefully this helps someone down the road!!