I have a 1984 325e manual with a B25 swapped in. The factory diff that is in the 'e is a 2.79 open differential. A couple weeks ago, I was at a junkyard picking over a wrecked 318i, and I noticed that it had a 3.93 LSD in it, but it was a small case. I pulled it out and bought it, scraped all the gunk off of it (1/4" layer!), and it's been riding around in the trunk of my GTI since then. I figured that even if I don't use it, it's still probably worth something to someone and it's worth saving from being made into soup cans.
I've done research and it looks like the small case diff should be able to handle pretty much anything a stock B25 will chuck. The small case I have has a way shorter gear, is limited slip, and weighs like 25 pounds less than the factory medium case. I've used the search and found plenty of people swapping from small case to medium case, and it sounds like there's no issue with compatibility, but I never find anyone going the other way around. Is there any good reason why it would be a bad idea to run a small case diff on a stock M20B25?
I've done research and it looks like the small case diff should be able to handle pretty much anything a stock B25 will chuck. The small case I have has a way shorter gear, is limited slip, and weighs like 25 pounds less than the factory medium case. I've used the search and found plenty of people swapping from small case to medium case, and it sounds like there's no issue with compatibility, but I never find anyone going the other way around. Is there any good reason why it would be a bad idea to run a small case diff on a stock M20B25?
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