I have an 04 with the 4spd automatic. While towing my trailer(12,700#) over MT. Hood the trans temp went up to 240 degrees. On the way to Madras it was raining and the outside temp was cool, on the way back it was 85 degrees and sunny. It heated up both ways. The truck is a 3500 SRW with a tow package. What is causing it to get so hot.

 

First, where are you measuring the tranny temp?
Second, were you going fast enough that the TC was locked?

If you were going slow, as you should with such a heavy load on a mountain, the TC was probably not locked, and this contributes to the heat.

Chris

 

I don't know where the sending unit is installed, I had Camping World install it with my Pac brake. The tranny was in second gear and I was doing 45 MPH as per the owners manual. The trans fluid does not smell burnt and it was at the proper fill level. How do you know when the TC is locked up?

 

Have Dodge do a code scan if one of your warning lights turned on.

However, I do not think you have a problem if all you saw was the temperature go up on the aftermarket gauge installed in the line to the cooler. Transmission oil temperatures will run right up when you pull, but will be cooler in the return line and the oil in the pan will be well within the proper temperature range.

I prefer to install the temperature sensor in the lower transmission sump, but that is not where most folks do the installation. Most are in the line to the cooler, and that reads the hot fluid as it leaves the converter, so is grossly inaccurate.

I think nothing about 340 degree fluid in the line to the cooler, and would expect the returning fluid to be something on the order of 190 degrees.

 

The tranny will lock up in third gear, if you have OD locked out, otherwise it only locks on 4th. You should see a noticable RPM drop when the TC is locked, and when you give it fuel the engine RPMs go up slower, more closely to the speedo going up. When not locked and you give it fuel, the RPMs will jump up a few hundred RPM before the truck starts going faster.

Chris