Trans cooler line question..

On a TH-350 trans is there any particular reason to use either 5/16 or 3/8" hard lines for trans cooling? Thanks

 

No need to use hard lines. I'm using # 4 AN fittings and Earl's stainless hose. Jegs has a kit with hose and fittings to adapt to AN fittings.

 

That's an option, what I meant was one size preferable over another

 

Factory uses 5/16 steel on everything I can remember. 3/8 would be more difficult to work with, without any real benefit.

 

use whatever works for you , either 5/16 or 3/8 will be just fine

 

Some people use bigger lines for added volume.

 

I ran all 5/16. Everyone sells it and it works perfect.

 

Added volume and slower flow through the lines. Slower flow through the lines means more time in the cooler.

 

One more thing. Don't over tighten the fittings in the trans!!! The bosses where the fittings screw in are thin, and will crack. Crack = leak. Thank God for JB Weld!!

 

3/8 vs 5/16 using a pair of 6' lines the volume difference is a little over a tenth of a quart.

 

True, But it cant hurt...

 

Not true about more time in the cooler. The cooler has fixed tubing size and will flow the same rate through the cooler itself. The line size does have an effect on the flow speed in the lines only.

 

I think it's real important to use a good quality tube bender. Size 5/16.

 

Ok. How about "More time out of the transmission for cooling purposes"?

That kosher?

 

No. All you'd really do is make line fabrication 2x as difficult as it needs to be. The cooler is the cooler, the lines are not the cooler.

 

The bigger lines smoosh a lot easier than brake lines... ask me how I know.

 

Whatever size the thing is designed to take...why overthink stuff?
GM isn't stupid. (Well...back then they weren't anyway...)

 

Is there a specific in or out on an internal radiator trans cooler? Does it matter what direction the fluid run?

 

Pump to the top and the pump only has to lift the volume in the line. Pump to the bottom and the pump has to lift some/all of the fluid in the cooler depending on design (stack plate vs. S-bend). Basic rule of fluid transfer.

Factory lines pump to the top fitting.

 

from bulkpart.com

The most often asked question is should I bypass the radiator cooler when I install a auxillary cooler.
Most cooler manufactures and automobile manufactures information we have read, recommends installing the coolers In-Series with the factory radiator cooler for maxium cooling efficiency.
So unless the manufactures who have spent 1000's of hours testing different installations are wrong, the suggested cooler installation is in-series......
Transmission > Radiator cooler > Auxillary cooler > then Back to the transmission.
If you must bypass the radiator because the cooler tube is leaking or for other reasons, be sure to increase the size cooler you install by 1 to 2 sizes.