I just picked up a 1990 740 turbo wagon with 120,000 miles for $300.00. This has the AW71 automatic transmission. The problem is that the transmission will not move when in drive, it seems like it is just reeving up as if it were in neutral, the transmission will only work in reverse when it is cold . After about 2 minutes the transmission will no longer move in reverse and will start to make an interesting noise. The fluid is slightly over filled and looks cleaner, possibly recently changed, but the previous owner did not mention changing it. The previous owner told me the only problem he had was when it was cold the transmission would shift slower, then this current problem happened. Should I even invest money into changing the fluid and filter? The Kick-Down Cable Adjustment seems a little loose, would tightening it do anything? I am guessing that the valve body might be shot or clogged/sticking. Please Help! If I have to I can get a used transmission for another $300.00, are these hard to replace in the driveway?