I have continuing problems with the electric overdrive in a 1989 740 Turbo when it gets cold up here in Minnesota. Works fine all summer. When the temperature gets below 30 degrees F, the overdive will not engage until the car has been driven long enough to warm things (what things? I dunno) up. When it gets really cold, minus 20 F or below, it will never engage unless you warm the car up, then stand still with engine running for several minutes. Then it will engage once, but after moving for a couple minutes, things cool off agin and it won't engage. Makes it difficult when driving on country roads. The "overdrive" was replaced in 1994 at the end of extended warranty for this same problem. Didn't happen for a year, then began again. The problem has started accouring at higher temperatures this year than last. Dealer always checks the switch in the knob first, then offers complete replacement again, for big dollars. Is this Swedish car allergic to cold weather?

I assume the shift knob switch is OK because the dealer always checks it. (The car has always been dealre maintained.) I cannot think of a reason why the solenoid would be particularly sensitive to temperature. If the hydraulic (transmission) fluid is getting too stiff, why does it work alright for a year before problems surface? Should I change transmission fluid every year? Is there a particular fluid that will work better than others? Can anyone offer another solution? All help will be greatly appreciated. Apart from this, and a few creaks and rattles, the car is running great at 104,000 miles, and I would like to keep it.