I need to know what size the male fittings are that go into the side of the transmission housing for the cooler. I am going to put in an aftermarket cooler, so I will be running an NPT to AN adapter out of the tranny, then to steel braided line, to aluminum pipe, back to steel braided and then to the cooler.

 

I don't remember the actual size off the top of my head but it is a straight thread fitting, similar to AN fitting, don't use NPT or you will crack the tranny housing around the fitting.

Try a 1/2-20 or 7/16-20

The reason I know this is because I have cracked a tranny case by using a NPT fitting. I tried to weld it up with no luck because the case is cast aluminum, which is very difficult to weld.

 

If you have a 97 or later 4l80e with the center lube you will destroy the trans if you remove the oem cooler fitting. Reason is that the rear fitting has a nipple that extends past the threads and inserts into a seal in the center support. Without this style fitting you will not have lube to the rear of the case. Results....not pretty.

 

I have a 99 case. It's for a custom truck project, so I got the trans from a local guy selling it. I'll have to check if the stock fittings are still there on the side of the case. Hopefully they are from what your saying, but I'll definatly just use the quick connect fittings from GM either way.

 

like he says....better unscrew that back one and make sure it is different than anything you have seen before. I almost made the mistake of not getting one.