Vince,

Thanks for the info on the inra-red thermometers. I use mine for an estimatioon and I have verified its accuracy of measuring at least liquids with a mechanical thermometer and it seems to match to the coolant temp sensor pretty close. It is supposed to be accurate to +/- 3 degrees F, so I trust it to be in the gerneral region. If you have a source that says it is better to change it every 30k miles then that is fine, I am just stating what the general consensus of the mechanics is around here.

The reason the transmission temperature stays so cold in winter is because the coolant/ATF heat exchanger is built into the radiator on the cold side of the radiator. On my car, as with a lot of other MBs, the radiator is a cross-flow type. It flows from in on the driver's side goes accross the whole radiator, through the ATF cooler on the passenger side and back accross to the driver's side and out back to the engine. This means that after a drive at speed through the 30F air, the temperature of the coolant that the ATF cooler is submerged seems to be no warmer than 50-60F. The radiator at this point is very cold to the touch. There is no thermostat for the ATF so it flows through no matter what. The engine thermostat has a slight regulating effect in that it is further closed when it is cold out and thus there is less quantity of coolant flowing through the cooler and a higher temperature differential between the ATF and coolant so it does not become as cold as the coolant. However, the temp of this coolant is very cold on this part of the radiator and thus cooler trans temps. Tranmission temp seems to be dependent on 3 main factors, road speed, type of driving, and outside air temp affects it as well.

-Cheers

__________________
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record