My transmission fluid is leaking into my.

The Service Manager came to the same conclusion as you: bypass the original cooler and install an external one. I am scheduled to have it installed this coming Wednesday.

The Service Manager and I took the vehicle for a test drive earlier today to road test the wheel bearing repairs (all good there). The vehicle was cold when we set out for the drive. We didn't notice any shifting issues during the 10 mile drive which was somewhat mountainous. Right after I dropped him off, I put the Explorer in reverse and experienced the slightly harsh engagement that I had mentioned previously. Also, when I was starting up the fairly steep grade toward home, I noticed that the tranny hesitated a bit shifting from 1st into 2nd. I guess that was slippage. It definitely waited until the vehicle had heated up (and he wasn't in the vehicle, of course) before I noticed the shifting issues today. I was told that my computer never has shown any codes relating to an overheating condition in the tranny.

When I noticed the leaking back in August, I didn't have the harsh engagement and any noticeable slippage then. This started showing up in October or so. I am hoping that all of this is related to the cooler getting progressively more restricted over time. The Service Manager said that the restricted flow of fluid itself shouldn't cause shifting issues as far as the tranny not getting enough fluid fast enough is concerned but does agree that the fluid overheating is what is causing the vent hole leak. He did say that the valve body could also be a source of the harsh engagement and slipping but I hope we don't have to go there.

I will keep you posted once the new cooler has been installed. Many, many thanks for your technical insight along the way. :)