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I have a 2002 Winnebago Ultimate Advantage 40E equipped with a 350 hp Cummings diesel. I recently noticed that the engine coolant level was low. After adding a gallon of antifreeze and a gallon of water, I let it sit an hour. I then discovered the coolant level was down again, which prompted me to check the engine oil and transmission fluid levels. I found that the transmission was way overfull, telling me that the coolant is getting into the transmission.

I’d like to know if the RV (on a Spartan chassis) has a separate transmission cooler or if it is incorporated into the radiator. And, if it is separate, what does it look like? How do I get it out? What is the part number? And, finally, where can I buy it? Thank you.

Bob Venturini

Pawtucket, Rhode Island


Like most diesel pickups produced since at least the 1980s, the Allison automatic transmission in your coach uses a heat exchanger located within the engine’s radiator to help it stabilize fluid temperatures.

The internal heat exchanger is very efficient in removing heat, and it does double duty by warming the ATF after a cold start. Transmission temperature can vary greatly depending on how the vehicle is being used. Linking engine coolant temperature to transmission fluid temperature helps stabilize the large ATF temperature swings that would occur otherwise.

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Diesel World April/May 2019, Towing Exp : Duramax Cooling Upgrades, Frontline Defenders, Two Epic Tribute Trucks Inside, And More......