Hey guys.

I have a 1990 740 with the AW-70 transmission, and I am thinking of replacing the standard oil cooler for the transmission. The previous owner didn't replace the transmission-fluid that often, and now that I am doing a complete flush, I thought about replacing the old cooler with a bigger one. Hopefully the transmission will get better cooling that will make the trans last even longer.
The old setup is with the small cooler in front of the radiator that connects to the main radiator.
I am therefore wondering if the radiator has some sort of thermostat to make sure that the oil that isn't hot enough is passed back? Or is this not an issue on transmission cooling?
Also, the lines from the radiator to the tranny is quite thin and should I replace there metal lines with some thicker oil hose?

Any help will be appreciated

 

Well, unless you plan some heavy towing, and with the 114 horses in the car I rather doubt it, I would make sure that the cooling system is in good nick and the transmission fluid is fresh--there is no evidence that the stock system is inadequate under normal use. Unless of course you like to complicate your life...
There is no thermostat that performs the function you mention.

 

fwiw, the 1992 740/940's had a bigger radiator and tranny cooler than the earlier models. I dont' know what it would take to retrofit this radiator. it uses electric fan rather than a belt driven one.