Transmission line tubing size

Cracker289 · 03-31-2008

I am filling out an order form to buy 25 feet each of fuel line, brake line, and transmission line, so I can run all my hard lines on my 66. I know the brake line is mostly 3/16 with a few short sections of 1/4, and the fuel line is 5/16. But what size is the transmission line? Is it 5/16 also or is it 3/8?

The Greek · 03-31-2008

The stock trans lines are 5/16 inch. If you are going to run fuel lines on a 2 barrel stock engine 5/16 inch will be OK, but if there are any plans to upgrade the performance you will need to run 3/8 inch tubing. The whole system must be 3/8 inch including the fuel tank pickup and fittings or else you'll create a bottle neck. If only one small section is 5/16 inch, the whole system will effectively be 5/16 reguardless of the tubing size.

I'd also remove the small inlet filter on the tank pickup and install an inline filter that can easily be changed out. FYI the 3/8 inch pickup with fuel sender is available in repro form. Don't use copper for fuel lines either and NEVER for brake lines. Fuel additives have a chemical reaction with copper and copper lines can't withstand brake line pressures.

I'm thinking that you are aware of the fact that prebent lines are available for your applications.

Cracker289 · 03-31-2008

I thought about the prebent lines, but I don't have stock rear brake setup, don't hae stock front brake setup, don't have stock master cylinder, and I have a rear brake proportioning valve, so I realized I would have to do a lot of modifications anyway, so I decided probably easier in the long run to just do them all from scratch.

Thanks for your help though, and do you know if all Fords used 5/16th tubing for the trans lines? Did trucks use 3/8th? I need get a roll to do the lines in my F-100, it has a lot of sections done with rubber hose, I don't like that!

The Greek · 04-02-2008

I believe that trucks used the 5/16 also. The size of the cooling line ports in the trans housing were all the same for any particular transmission. If extra cooling were needed a heavier duty cooler was probably used instead of larger lines. The cooling line ports on the C6 trans may be larger, but all of the C4s that I've seen used 5/16 inch.

I looked at the assembly manual for the 67 with the 390 and C6. It shows different part numbers for the fittings that screw into the radiator tank. This may be an indication of 3/8 inch lines being used.

Cracker289 · 04-03-2008

Appreciate your help buddy. 2 rolls of 5/16 it is.

The Greek · 04-03-2008

You may want to go with the 3/8 inch fuel line and fuel tank pickup/sender assy. The Shelby GT-350 that had the HIPO 289 used the 3/8 inch line. If you have plans to increase the engine's output to or above the 300 HP level, it would be best to go with 3/8 inch. This is what I did. If you get bitten by the performance bug, you won't have to redo the fuel line.

Cracker289 · 04-03-2008

I know. What I meant by "2 rolls of 5/16th" was one for the trans lines on the 66 Mustang and one for the trans lines on my 69 F-100.

The Greek · 04-04-2008

Cracker289, I get what ya mean. Good luck.