4T65E Cooler Line Fitting Info

[bluegtp91]

Per Dave @ TEP:

 

Here's the low-down on cooler line fitting thread sizes.....

97-Most 99s:
 

Cooler FEED fitting (points straight down) 1/4-18 NPSF, NO CHECKBALL
Cooler RETURN fitting ( Horizontal-points towards front of car) 1/4-18 NPSF
 

Some 99s, all 00-early 04s:

Cooler FEED fitting (points straight down) 3/8-18 NPSF, HAS CHECKBALL
Cooler RETURN fitting ( Horizontal-points towards front of car) 1/4-18 NPSF
 

Early 04 to current:

Cooler FEED fitting (points straight down) 9/16-18 UNF, NO CHECKBALL
Cooler RETURN fitting (Horizontal-points towards front of car) 9/16-18 UNF

Since most of us are dealing with the 97-03 model years here is the easy way to know what you have:
 

If you remove the FEED cooler line (points straight down and also almost all of these have quick connect fittings, very few were thread in lines) and you see some type of retainer, spring, and check ball in it and can NOT push a small pocket screwdriver or similar straight through the fitting then you have a fitting and matching case with the 3/8-18 thread here and here only. The return fitting is a 1/4-18 thread on all 97-early 04 cases. You MUST USE A FITTING WITH A CHECKBALL IF THE TRANS CAME WITH ONE!!!! The ONLY exception to this is if the transmission is apart and being rebuilt you can install an internal check ball like what was used on the 97-99 and 04+ units. It is in the channel plate. It doesn't matter where it is located but there has to be one in one spot or another.

If you remove the FEED cooler line (points straight down and were all thread lines on the 97-99s) and you CAN stick a small pocket screwdriver straight up i.e. no check ball or spring in the way then you can do what you want with aftermarket fittings and the threads will be the same smaller size on both holes in the case which are 1/4-18 NPSF