what is the best way to clean/flush the transmission cooler inside the rad.

 

assuming that its been sealed up and in use, i'd disconnect the transmission lines at the rad. put a rag and bucket under the rad connector as best you can. then use an air hose and blow air into the top port. you should get a nice mess coming out. this will be a backflush to the oil's normal flow.

consider removing the check valve on the pressure line. the one that goes into the bottom of the rad. its at the junction of the short rubber hose and the hard line, right at the frame. its about the diameter of a quarter and about an inch long. you may have to rig up a way to reconnect the lines - i don't remember what the fittings are like. i cut mine off and replaced it all with 3/8" transmission hose and regular hose clamps. the check valve is a place thats likely to get clogged up and shut off oil flow.

 

3/8'' flame to 3/8''FIP converter and 3/8'' MIP Barb is the Check Valve Delete.



I would also add an external filter, like I did.