I need a new Dif!!!Help Please.

[Swapped TI]

I just finished my engine and tranny swap. I have a96' TI that had an M44 and auto tranny. I swapped it for a 92 325i engine and manual tranny. I was so excited to drive it until I drove it 32 miles and used 1/8 of a tank of gas. The revs are so high its really silly. My question is, I have a 99 maunual TI sitting at home as well I have to do some work on. Would swapping the differential off the '99 (which from my understanding the auto is 4.44 and the one in the Manual is 3.45) be any better? or does can some people chime in who have done a swap and let me know what made you happy.

[wolferj-RIP]

Temporarily, the 3:45 will be an improvement, but it's a small case diff that can fail easily, due to the extra power from the 6 cyl. What you should look for is a medium case diff with the ratio you want. The 3:45 ratio is a decent all around choice, most would not recommend going higher than 3:73.

I went with a 2:93 ratio diff, as I drive at freeway speeds alot... still manage about 22-25 mpg with a M50 swap...

[cooljess76]

You can swap the diff from your manual ti and it will work fine as long as you're gentle. Keep in mind that it's a small case diff and it isn't designed to handle the extra torque of the 6cyl. Later down the road, you should upgrade to a medium case diff out of an e24, e28, e30 or Z3 Roadster or Z3 Mcoupe. Note, when you upgrade to a medium case diff, you'll need to run e30 or Z3 halfshafts since the medium case diff is wider and requires shorter halfshafts. This may require swapping output flanges depending on which model the diff came out of. For instance, if you get a 3.73 LSD out of an e30 325is, you'll also want to get the halfshafts from that same car. If you get a 3.23 LSD out of a Z3 or Mcoupe, you'll want to get halfshafts from that car since the bolt pattern on the halfshafts will match the pattern on the output flanges. now if you get a 3.25LSD out of an e28 or a 3.46LSD out of an e24, you're going to need to get halfshafts and output flanges from a 6cyl e30 since the e24 and e28 halfshafts will more than likely be too long. Also not, e24 and e28 diffs have a different style hanger mount and will require you to swap rear covers with a 6cyl e30 or Z3 diff for it to work. The manual e24's and e28's offer the best ratios(3.25 and 3.46), however they require a little more sourcing of parts(cover, halfshafts and flanges). Hope that helps. There's some good writeups in the knowledge base section as well as the differential section on this forum. Best of luck!

-Jess

BTW, Congrats on your swap even though you just bastardized your '96 OBDII car with a '92 OBDI engine. FWIW, that's a really crappy thing to do. Now not only is your car illegal, it's also worthless when it comes time to sell it. Oh well, your car not mine