::: DRO ::: Tech Section - Project 4-Link

The next thing on the pump that needs some attention is the priming valve. The valve and spring are retained by a small roll pin that is driven through the pump housing. It is prone to fail and when it does you have no pump pressure and the transmission will not function. Here is what I recommend to prevent a failure.

The small roll pin is a weak link in the front pump. The fix is described below and is a good investment in time and it cost us only $2.50 to make the improvement.

Disassemble the priming valve by using a punch and knocking the pin out. Keep you finger over the top of the hole so you don’t have to hunt for the spring. Set the spring and valve off to the side.

Next step is to tap the hole the valve came out of with a 1/4"” NPT (pipe thread) tap. No need to drill the hole, the tap will fit perfectly. Get an Allen-head 1/4"” NPT steel plug, drill a 3/16” hole through the middle of it and deburr it.

This simply shows the 3/16" hole in the Allen head plug.

This is the tap being put in place, the hole is already the correct size for the 1/4"” NPT tap.

Take your time and tap the hole deep enough so the end of the pipe plug will stop at the bottom edge of the hole the roll pin was in. When that step is done you will need to take a small round file and work it in the tapped hole to take the sharp edges off the threads until the priming valve will slide down into its original position. Be sure to lubricate the valve with trans fluid or assembly lube as you trial fit it. It will take a few minutes to get it to fit so take your time and take off a little at a time.

A small round file being used to deburr the edges of the threads so the valve will fit back into the hole we tapped.

This is the finished priming valve update. The weak link has been removed and you have added reliability to your front pump with about 20 minutes of work.

When it will slide in with a slight pressure take it apart for the last time and blow all the metal debris out of the passage. When putting it in for the final time be sure to coat it with trans fluid or lube, put the spring on top of the valve and turn the pipe plug in until it stops at the bottom of the roll pin hole. Now you have just prevented a lot of frustration that might have occurred if that roll pin broke and you had to take the transmission out to see what was wrong.