Here is the story. my lovely 42rh trans went out and while in the process of removing it for the rebuild i busted both transmission lines near the transmission.

I am going to replace the entire line (Transmission to cooler)with new steel line but here is where my question comes into play.....

What size should i use. Ive read that going to 1/2" oil resistant hose is better and reduces back pressure and overall helps cool better.

Should i upgrade to the 1/2 steel line? Or stick with the stock 3/8".

My aux cooler has 3/8 barbs but i can easily adapt down to 3/8s trans hose for hooking it up.

 

The larger size tube is worthless unless you upgrade the cooler and any other restriction points to the new size. With that in mind, if you can afford it go for it, if not stock is just fine.