I'm thinking seriously about buying someone's old rusty 1978 240 wagon, to use as a winter beater and preserve our 1978 244 in pristine CA condition. I haven't actually gone to see the car, as it's three hours away, but the pictures look decent and the owner seems like an honest guy --- and the price is so low as to be in "what the heck, I could part the dang thing out and make money" range.

One part I really want is the M46 trans, which I intend to put into our pristine 1978 if and when the lame BW55 slushbox ever fails. But the seller says his M46 has a weird problem: the OD works pretty well in cold weather, but doesn't stay engaged in hot weather. That sounds to me like a bad seal that won't hold when too soft from the heat. I had that problem on my old 1983 244 (RIP).

Any thoughts about this? I couldn't care less about OD on the winter beater, as I'll just be driving it around town. But it would be really nice to have on the sedan, as it would finally turn that car into a true freeway cruiser. Am I looking at an OD rebuild to make it work right?