I have a 2002 SuperCrew with 54k and the transmission gets hot when driving above 70 MPH. The temp will rise to 250+ unless you shift out of OD or slow below 70 MPH. The temp reading is via an Edge CTS.

Yesterday, after driving about 20 miles above 70 MPH, I looked in the mirror to see a cloud of smoke behind me. I pulled over and all the fluid in the tranny pan was gone. I assumed the tranny was toast and I did not want to load the truck on the interstate, so I drove about 2 miles to the next exit at 35 MPH. The tranny shifted normally - which seemed odd since it the fluid in the pan was now missing.

After refilled the tranny with fluid it is like nothing happened. The truck is at my parent's home a couple hours away, so it is going to a local mechanic tonight to have him check for the source of the fluid loss.

Anyone have a good guess on the source of the problem? I plan to take the truck to a tranny shop when I have time to get it back.

 

You were driving 90 MPH?

 

MPH is a common abbreviation for Mile Per Hour. So 20 Miles above 70 Mile Per Hour would not mean 90 miles per hour. Rather, it would mean traveling a distance of 20 miles at a ground speed of 70 Miles Per Hour or greater - e.g. never reducing my forward momentum below a measurable rate of speed equal to traveling a distance of 70 miles or more per 1 hour of travel time. Hope that clears it up.

 

sounds like somethings up with the transmission cooler or the lines leading to it.

 

That is my suspicion also. I thought a line must have blown at first, but when it did not leak after a refill, that got me stumped.

Here is the strange part - I drove the truck all the way across town today to the transmission shop and the temp never moved above 135 degrees. The truck has never run that cool before. It always stayed above 160.

At this point, I am wondering if the cooler or a line was partially plugged off and getting the transmission hot finally cleared it out. If that is the case, I hope it did not fill the transmission with junk and cause it to fail in another month.

The first owner only drove the truck 47k from 2002 - 2010 - so the truck definitely sat around a lot.

 

I dropped the truck off at the tranny shop and they said it needed a rebuild without looking at anything because the fluid smelled like "rotten eggs". Seeing how the transmission was working flawlessly in every situation except driving above 75 MPH, I was not sold on the idea of a $1500 rebuild yet.
I had the shop check the flow on the cooler and drop the pan. They called me back an hour later and said the cooler was flowing withing spec and the pan was absolutely clean.
I had them flush the transmission with 20 quarts of fluid so I was sure to get all the old stuff out. The tech did a test drive, got out and said "I have no idea what is going on because it seems perfect now".
I drove the truck directly from the transmission shop to the interstate, put the cruise on 85MPH and drove about 30 miles. The temp did get up to 220 when climbing a few big hills, but it stayed within 10 degrees of the engine coolant temp the rest of the time.
When the speed was dropped to 75, the trans temp dropped to 160 and stayed.

The truck has consistently ran 180+ (before it boiled the fluid out) - now it runs 150-160 on the highway and 120-140 in town. I have no idea what happened when the tranny got hot enough to boil the fluid out, but it fixed the transmission as of this point.

As much as I think my Edge CTS is a way overpriced toy - I think it might have saved me a transmission. Not a single dummy light or buzzer went off when the transmission was hot enough to boil the fluid. I guess the edge might have paid for itself on this one.