Transmission Cooler failure
 

A while back, I noticed my transmission was failing to engage/slipping in first gear. I checked the dipstick, and found that it was 2 quarts low.

The truck has 192,000 miles on it, so I figured I had a leak somewhere. I just added 2 quarts of transmission fluid and kept driving. The transmission worked like normal after that.

2 weeks later, I notice the same problem, and again, the transmission is about 2 quarts low. I looked underneath the truck, and found it to be completely clean... but then I checked the degas bottle...

I upgraded the radiator with a 2 row one from Autozone and flushed the coolant. I am about to do a transmission flush, but I was wondering if I have to do a pan drop?

I was just going to do a fluid exchange through the auxiliary cooler. .

Attachment 4645

In this case, I'd drop the pan, clean it out, and change the filter.

Here's some carnage from today.

Attachment 4643

I did have some concerns. I performed the DIY flush method as outlined many times on the forums here, and the fluid never really came out looking new. It was certainly much redder than in the picture, but it still looked milky...

I used up 14.5 quarts, but then I had to stop because I ran out of new fluid.

Because this is coolant mixed with transmission fluid, does this mean I just need to run more fluid through the transmission than normal to complete the flush?

Yep - likely much more.

Go find some cheap Mercon V (Wallymart Supertech brand is fine).

Woon't do the pan drop/filter change until it runs clear.

MGD

This MIGHT be one of the times I'd actually recommend a flush and not just an exchange.

I'm gonna lean heavily on the MIGHT because this transmission is olllllllld, and I'm worried about the flush horror stories, even though I've been changing the fluid regularly.

I really would like to see if I could wring at least 275,000 out of it tho.

I'd hate to imagine that a routine failure like a radiator would render the truck undriveable in such short order.

I get a single clunk coming from somewhere in the back half of the truck when the transmission shifts from 2-3. What could it be?