Journal-News

Wheels: Lars of Dayton writes by e-mail: "I have a 1998 GMC Savanna conversion van with a 5.7-liter engine and a trailer towing package. I tow a Coleman Caravan trailer (approximate weight is 4,500 pounds) with the van. On a trip to Maine, when refueling, I started to check the transmission fluid. The dip stick was so hot it burned my hand. The fluid was still pink, and engine temperature was normal.

On the next trip, the transmission fluid was tan. The engine temperature also would rise — at one point to approximately 245 degrees. I have had the transmission serviced and added an auxiliary transmission cooler. The engine temperature remains normal under normal operations but overheats anytime I pull my camper."

Halderman: It would be very helpful to drive with the transmission selector in the "drive" (D) position and not in the overdrive (OD) position. When the transmission shifts to the overdrive position, more heat is being created in the transmission when the torque converter clutch (TCC) is off.

The TCC is commanded off if the vehicle is under a heavy, load such as when pulling a trailer. Therefore, if you have been towing the trailer using the overdrive shifter position, then you may not have a problem. Just be sure to not select the overdrive position whenever towing.

If the temperature of the ATF is still higher than the engine coolant temperature, then the cooler inside the radiator may be partially restricted. I would guess that the auxiliary cooler was connected in series with the one in the radiator and therefore this would not help the situation.

To test it, you could disconnect the outlet line and divert the flow to a large container. Then open several quarts of automatic transmission fluid (ATF) and using a funnel, be prepared to add fluid as it flows out.

Start the engine. There should be a flow of two quarts every 60 seconds. If less than that, this means that the cooler is restricted. Many shops use a transmission exchange machine that can show the rate of flow. This is less messy and a more accurate method to use to check for cooler restriction.

James D. Halderman is an ASE-certified master technician and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.