I've been enjoying my-new-to-me 1991 350SD for a few weeks now. I'm slowly working thru the little issues but there's really just small stuff to fix. I like everything about this car. What a solid car this is! The only thing I would want is an overdrive 5th gear to drop rpms at highway speeds. It's not really a big issue but I think it could be a great upgrade.

I've found some old posts related to this but they went nowhere. So here's my question: would the 722.5 fit on a OM603? Has anyone done this and if so, how complicated is it?

The fact that there is little information available about this may mean it just doesn't fit or wouldn't hold up. Any input appreciated, thanks in advance!