I need to replace the automatic transmission cooler hoses the metal lines are fine. I’m having trouble figuring out what the inner diameter size is.Went to autozone they had no clue. I was just going to buy high pressure hose and cut to fit. 04 4.0 4x4

 

3/8's ID hose is what you want, and high temp hose not high pressure

The trans cooler lines don't have "pressure", there is a lot of flow so some "pressure" just from volume

The way it works is the transmission pump generates about 200psi pressure, that pressure is sent thru the valve body which routes it to engage and disengage clutches and brakes(bands) and hold them in place.
After its used it flows out one cooler line and then back in to the open pan at the bottom of the transmission, at 0psi, no pressure in pan, then its sucked back up by the filter to the pump

But it does run at 190-220degF, so about the same as engine coolant

 

Perfect ! Thank you.

 

I see that 3/8 id is the recommended hose size, but I have to replace some sections of the steel tube also. Is it 5/16 O.D. or how should I specify when I go to auto parts store?

Thanks

 

@RonD
Related question; please confirm or correct as needed:
Using AutoZone\OReilly supplied hose stamped "FuelLine PCV\EEC 3/8inch\9.5mmID",
with stock metal ATF tubing sections from RadiatorExchanger & then back to Tranny,
for stock TrannyCooler + 2nd stock TrannyCooler mounted left+right behind grill,
hosed up parallel with 3/8InchStainlessHoseBarbTees & dual WormClamps on all Hose~Barb connections?
This is a 2001 V6~4.0L~SOHC+5r55e.
Thanks

PS: Thinking about taking RadiatorExchanger out of this ATF loop.

 

Transmission cooler lines should only have 5 to 40psi pressure, so barb fittings are best and hose should be rated that high
Radiator Trans-cooler is also used to keep transmission fluid warm in colder climates
Like engines run best with coolant between 190-210deg, automatics like 180-200deg fluid
Lower radiator(or return side) coolant should run about 170deg fully warmed up, which is were trans-cooler is located, so it would also cool ATF Fluid, but it can also keep it from dropping below 170deg

ID and OD are not really related, it depends on how thick the walls of the hose or pipe are
So a 5/16 OD hose may or may not be 3/8 ID, so not sure how to answer that one

 

That must some fancy hose, inside diameter bigger than the outside diameter.

 

Hoses with InsideDiam larger than OutsideDiam?
Maybe those are only on exotic 1/2Million$ EuroSportCars, that I can't afford to touch?
Maybe today RonD just needs another CupO'Java & is just thinking BassAckwards or writing too fast?