Upgrades: differentials and limited slips!

[Green Dragon]

Originally Posted by dabenthusiast

When you say manual diff is larger, how do you mean.
I have pre face-lift manual diff... if I wanted to do the 4.4I diff do I just swap them out? Or bust open and replace internals.
And would I need to buy 4.4i axels ?

The manual diff (rear) is a large case (I know for sure on the post-lci), while the auto diffs are a medium case I believe. I'll post some comparison pics tonight. Both fit interchangeably without doing anything. Direct swap. The one thing I don't know, is if the pre-lci 3.0 axles will mate up with the pren-lci 4.4 diff. You'll need to compare part numbers from real oem, etc. It's possible in your case that you can just pop out/pry out the output flange cups and swap them interchangeably. My e36's all did this between diffs but the e53 could be different, which it was in my case.

Worst case scenario you buy new rear axels for the 4.4 diff. I do belive reading from Sedec's posts, you don't need to if your prefacelift and using prefacelift diffs, making your swap easier. Let me know if that helps. I will post some pics tonight. Front diffs match up, no issues as long as you are post 2000 and on.

Also, you can just slip the front diff through, but I had to lossen the engine mount and Jack up on the motor slightly. No big deal.

[bcredliner]

Just so my pea brain gets it right--- am I correct that 2002 3.0 4.10 gears from an automatic is a plug and play install in my 2002 4.6? Assuming I have that right what other years are direct swaps with no alterations?

[Green Dragon]

Originally Posted by bcredliner

Just so my pea brain gets it right--- am I correct that 2002 3.0 4.10 gears from an automatic is a plug and play install in my 2002 4.6? Assuming I have that right what other years are direct swaps with no alterations?

BC, When swapping to 4.10 ratio, '01 till 9/'03 diffs should be plug and play. You only have axel issues when you get a facelift 4.10 diff. Double check part numbers on the axels, as I haven't compared the 4.6/4.8 diffs and axles. You may have beefed up parts that I haven't accounted for. A quick cross check on real oem should have you sorted. I'm just going off memory when I did my conversion over a year ago. Haven't had a single issue. I'd love to hear how your 4.6 does on the 4.10's. If 3.91's aren't enough, the 4.10's will liven things up for sure.

[Willie G]

If I may, a quick question: How have you accounted for the gear change affecting the speedometer? Or do you just live with it?

[bcredliner]

Originally Posted by Green Dragon

BC, When swapping to 4.10 ratio, '01 till 9/'03 diffs should be plug and play. You only have axel issues when you get a facelift 4.10 diff. Double check part numbers on the axels, as I haven't compared the 4.6/4.8 diffs and axles. You may have beefed up parts that I haven't accounted for. A quick cross check on real oem should have you sorted. I'm just going off memory when I did my conversion over a year ago. Haven't had a single issue. I'd love to hear how your 4.6 does on the 4.10's. If 3.91's aren't enough, the 4.10's will liven things up for sure.

Thanks for the info. I found a guy that will build custom ring and pinions but it is expensive. I would like to stay with a gear set that is not custom but I am not sure 4.10 is going far enough for what I want. Got to do some calculations to find the difference in RPMs at 80mph. That's the don't get run over Dallas tollway cruising speed.

[bcredliner]

Originally Posted by Willie G

If I may, a quick question: How have you accounted for the gear change affecting the speedometer? Or do you just live with it?

In the past I have done nothing to correct the speedo or in the good ol' days we changed speedo gears. Don't know If the speedometer can be re-calibrated with BMW software I will do that if possible but I am fine if it is off. Usually it's safe to run the speed of vehicles around me.

[Willie G]

Originally Posted by bcredliner

In the past I have done nothing to correct the speedo or in the good ol' days we changed speedo gears. Don't know If the speedometer can be re-calibrated with BMW software I will do that if possible but I am fine if it is off. Usually it's safe to run the speed of vehicles around me.

Thanks! My thoughts exactly.

Just surprised that I can't find anyone on the web who has managed to change the speedo....

[bcredliner]

Originally Posted by Willie G

Thanks! My thoughts exactly.

Just surprised that I can't find anyone on the web who has managed to change the speedo....

I think those who use the INPA suite on a regular basis could provide instructions. The reason the instructions aren't out there probably is because so few change gear ratios.

[crystalworks]

Interesting. So you are going to taller gears redliner? Wondering how different that would feel... factory is the 3.91's if I am reading the above correctly? I'm sure you are unconcerned with MPG... these tanks aren't great on that anyway. Some extra jump off the line could be very compelling. Interested for sure.

Did this on my auto Mustang GT (travesty, I know, it was purchased before I could drive manual)... and it made a huge difference.

[bcredliner]

Originally Posted by crystalworks

Interesting. So you are going to taller gears redliner? Wondering how different that would feel... factory is the 3.91's if I am reading the above correctly? I'm sure you are unconcerned with MPG... these tanks aren't great on that anyway. Some extra jump off the line could be very compelling. Interested for sure.

Did this on my auto Mustang GT (travesty, I know, it was purchased before I could drive manual)... and it made a huge difference.

Going to shorter gears. Taller gears would be going from 3.90 to 3.36. Yes factory gear ratio is 3.90 on 4.6. Have never had a car that was stock or got good MPG stock. I check it only if I am concerned there is a problem that isn't showing symptoms.