A few weeks ago the AW70 transmission in my 740 NA wagon started slipping. I was close to home and managed to get into the driveway just as the slippage became 100%. Over the next few days I found that attempting to move the car at any speed beyond idle results in a whine from the transmission and no motion. However at idle the car will move, so now it is in my garage.

The first clue was the presence of what looks like chocolate milk in the coolant recovery tank. I drained about a quart of coolant from the radiator by disconnecting the bottom hose to the coolant tank. The drained coolant has a top layer of brown gunk, below that the coolant is normal color. Im pretty sure the brown gunk is ATF, it doesnt look like engine oil. Next I disconnected the transmission cooler lines from the radiator, then pressurized the radiator to 15 PSI with my air compressor. I expected a hiss or leak from the transmission cooler ports - but there was nothing. The radiator was pressurized for about 15 minutes; I even used a short hose on the bottom port to refill the cooler with ATF - still no bubbles.

ATF must be getting into the radiator some way - but its not obvious how that is happening. Is it possible the leak only happens when the radiator is hot ?

I think the next step will be to remove the transmission pan and see if anything is obviously wrong, such as a clogged filter. Any advice would be appreciated.

Thanks,

Mike

1991 740 wagon (320K)
1993 940 wagon (200K)
1994 940 wagon (110K)