Thread: Pressure in transmission cooling lines

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I have a 1968 C-10 pick-up truck with a 237, 400 automictic transmission in it. Have had it for about 2 months. It has, at the radator, rubber hoses that are conneckted to the 5/16 metal tranmission lines. I guess someone in the pass change the radator. Could not get lines off old radator. So cut the metal lines and replace them with the 5/16 rubber hoses. I never did like it but figure it would be okay untill I pulled motor out this comming summer and put new lines in when the motor was out of truck. The other night, the top hose came off. Transmission went eveywhere. I seen that the metal peace that was in radator was only a short part of cut off line. So I bought two of those brass fittings with the big flare and put them in radator and also put on two new 5/16" rubber hoses. The top hose is about 12" long. The bottom hose is about 6" long. It looked to me like the old hoses had been on there a very long time. maybe 5 years or so. So I started thinking maybe the hose just did,nt come off. But maybe the presssure in the cooling lines got real high and blew it off. Pressure in the cooling lines is somthing I,ve never thought about before. Will the pressure in these lines go way up at times for some reason. Shold I not wait untill this summer to replace with new lines. But do it now. How would you advise me. Thanks John.

I don't use rubber hoses for trans cooler lines for the very reason you mentioned, they come off. An inexpensive hand tubing bender and new steel lines and fittings is the best way to go. Just like rubber fuel lines, they can save you a little time and money now, but cost you a bunch of both when they fail !!!!!!!

there is very little perssure in the cooler lines Johnwalkeasy, i all ways use 3/8 hose, and have had good luck with it. you need to do what ever makes you happy.

Yeah, Dave is right about metal lines being the best way to go, but if you insist on using rubber hose, buy hose designed for trans coolers, not fuel line. And to keep the hose from blowing off the existing metal line, use a flaring tool to put a little flare on the end, push the rubber hose a few inches over the line, and double clamp the hose.

I had to do this when I swapped the 5.0 Mustang engine into my Jeep truck, and it has been on there for 3 years.

If the part on the trans cooler is too short, buy a barbed hose fitting that screws into the cooler, and the barbs on the fitting will dig into the inside of the hose, preventing the problem.

Metal is the best, though.

If you want something fancy and flexible, use hydraulic hose, most is rated for 3000 psi.

Good plan, 1500 !!!! I'm sure hydraulic hose would take all the heat and pressure an auto tranny would ever put out!!!! Thanks for the tip.......

Hydraulic hose is not a real good idea. Its too stiff, and can wrench the cooler loose from the rad. Won't leak trans fluid, but antifreeze is vital too!

Transmission oil line hose available from your local auto parts store is wire reinforced, and is plenty strong enough. Line pressures to the radiator or external cooler are generally 50 psi or less.