46RH/A518 Cooler Lines

[gtxdana]

I'm rounding up enough parts to do a 727 to 46RH swap in my 70 GTX down the road. Is it really necessary to upgrade the cooler lines from the stock 727 5/16" to the 46RH 3/8 size? It looks like a lot of people just run the 5/16" lines.

I thought I saw a post where someone had a vendor bend up a set of lines in 3/8" but I couldn't find it again. Trying to keep the car stock appearing, so no braided or rubber hose. None of the parts houses around here carry any 3/8" steel tubing long enough to make a one-piece line. Not interested in using NiCopp.

 

[lemondana]

I've heard the 3/8 is needed for the overdrive unit.

 

[1 Wild R/T]

I had Fine Lines make me up a set of lines back in 2000... And yes, I posted a thread mentioning it years ago.... Last time I spoke with Fine Lines they were no longer interested in doing custom work....

A buddy tried using 5/16" lines, his trans got really hot on the first Lon drive while climbing a grade... He went back & replaced the 5/16" lines with 3/8" & it's been fine since....

Oh, most stock Mopar trans coolers in the radiator have 5/16" fittings, adapters will restrict flow, I had a local radiator shop swap in a GM cooler that has 3/8" fittings built in..

 

[gtxdana]

I figured the overdrive was probably the reason the factory went to a larger diameter line.

The radiator I'm using has 1/4" NPT fittings into the cooler which an inverted flare adapter for a 3/8" tube could be used. The passage into the cooler itself is slightly smaller than the passage through flare adapter. I supposed one could spend the $800 and plumb in that reproduction hemi transmission cooler with 5/16" lines.........or build some hardlines for an aftermarket cooler for a lot less money to cool the fluid.