I have a '92 wagon, non-ABS with around 150k and change. The first half of its life was spent on the salty winter roads of eastern Ontario Canada, so it has some rust issues. Nothing terminal by any means, but it's not pristine underneath. I've already replaced the front control arms, and I'm doing the trailing arms next.

Now, there's a '91 245 SE at a local Volvo shop. It's one of those cherry red "Special Equipment" wagons from '91. Beyond the alloy wheels, black leather interior, and factory roof rack, I'm not sure what the special equipment is. Anyway, it's a pristine low mileage example with no rust at all underneath. The front end was damaged due to a minor impact crash and so it's being parted out. I can get the trailing arms and the rest of the rear suspension, but I was quoted a really fair price to swap out the whole rear end, including the differential and axle. So I'm seriously considering it.

Here's my question, my '92 245 is a manual, and the '91 SE is an automatic. Should I be concerned about gear ratio compatibility or any other issues if I go ahead with a straight rear end swap here? Thanks for your advice and info.