Help - C4 cooling lines - thread size into trans (2024)

jcwalsh1

Sr. Member

Joined: Jun 4, 2003

Messages: 384

Loc.: Shawnee, KS

Sep 20, 2006

Any help would be appreciated.

I recently installed a Ron Davis radiator in my 75. I was told that it was a drop in copy of the stock rad. It fit in the mounts fine, but the fittings for the transmission cooler were 1/4 NPT. Much larger than what was in the Bronco. I bought earls fittings thinking I could use the existing hard lines. Well, the existing lines are 5/16, too large for a 4AN and too small for a 6AN.

I was thinking of replacing all of the lines with new 3/8 tubing, but I need to know if I can get the correct fittings to attach to the C4 or Are there other fittings I should be using in the radiator?

Jeff

ugly74

Bronco abuser

Joined: Apr 17, 2006

Messages: 2,847

Sep 20, 2006

I bet you could find the pieces you need to hook it up at Home Depot some other hardware store. all the pieces I used to plumb in my tranny cooler I found in the brass section of home depot.

you could always cut the metal lines back a bit, put a flare on the ends, then use the rubber line, with barb fittings on the radiator.

SurfCityEB66

Contributor

Sr. Member

Joined: Jul 18, 2005

Messages: 461

Sep 20, 2006

Jeff,
I just went through the same set-up. I used dash 6an fittings with steel braided lines. Specialty, Earls, they all make adapters to go from 6an to the pipe thread on the c4. Good luck
Brian

NYLES

Bronco Guru

Joined: Aug 13, 2004

Messages: 9,846

Sep 20, 2006

There is a such thing as a 5"AN", but remember "AN"'s and "NPT"'s will not work together........Also you can order fitings that are NPT on one end AN on the other.....bout $5 a piece.....Look in Jegs under fuel line and fittings.

Last edited: Sep 20, 2006

jcwalsh1

Sr. Member

Joined: Jun 4, 2003

Messages: 384

Loc.: Shawnee, KS

Sep 20, 2006

Does anyone know the thread size? 1/4NPT?

rcmbronc

Contributor

Bronco Guru

Joined: Dec 15, 2003

Messages: 2,717

Loc.: Tomah WI

Sep 21, 2006

The threads on the transmission are alot like 1/8" NPT or 1/4" NPt cant remember which. The difference is that they are not tapered like pipe thread. I used the stock transmission fittings and bought some AN adapter fittings that were AN on one end and inverted flare on the other to attach to the stock fittings. I then ran braided steel.

Here is a link to a previous post.

http://classicbroncos.com/forums/showthread.php?t=51471

MikeEB

Sr. Member

Joined: Apr 29, 2005

Messages: 414

Loc.: Grand Junction, CO

Sep 21, 2006

I took some of the premade brake line that they sell at Napa bent it and cut it down and then mounted soft line to that works real well and mounts clean into the tranny side, also helps direct the lines going straight forward so no kinks.

scsm76

Bronco Guru

Joined: Oct 6, 2005

Messages: 1,433

Loc.: Shaver Lake, CA

Sep 21, 2006

the fittings on the stock cooler lines are not AN, they are a standard 45* flare fitting. AN fittings are 37*. If you still want to run your existing lines your local auto parts should have the fiiting. They would be brass though and with a alum. rad you should use SS or Alum. Male 1/8" NPT to male 5/16 flare would make the connection to the rad. the transmission has 1/8" NPT thread and the adapter is a male 1/8" npt to female 5/16" inverted flare.
If you are going to all new lines you will need 4 male 1/8" npt to what ever size line you run (3/8 would use 6 AN) also need the ends for the hose. Or you could leave the trans adapters then you need a 5/16 inverted flare to 6 AN. Just route them carefully away from exhaust and electrical if it is steel braided.

broncbusted

Jr. Member

Joined: Mar 23, 2004

Messages: 125

Loc.: South Carolina

Sep 23, 2006

jcwalsh1 said:
Does anyone know the thread size? 1/4NPT?
Click to expand...

The thread size that screws into the transmission is 1/8" BSP. It requires an o ring to seal the fitting. You can find them here: www.pegasusautoracing.com

scsm76

Bronco Guru

Joined: Oct 6, 2005

Messages: 1,433

Loc.: Shaver Lake, CA

Sep 23, 2006

I stand corrected, sorry for the misinformation!

HotWheels

Bronco Guru

Joined: Jul 8, 2003

Messages: 9,179

Loc.: Twilight Zone

Sep 25, 2006

I have some extra fittings that I had ordered (had to order 10ea). I did the same thing with the Earls fitting and some Goodyear Hi-temp hoses.

I added a B&M tranny cooler in the return line also:

taxx

Sr. Member

Joined: Sep 18, 2004

Messages: 796

Loc.: Indianapolis

Sep 25, 2006

I just used nipples on the transmission with NPT thread (1/8th or 1/4 can't remember which) and ran 5/16th rubber line between the cooler and the tranny. Works great and doesn't leak and costs $10 or less.

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