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      03-21-2024, 12:10 PM   #1
ayao
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1M aftermarket rear differential

I came across this 1M for auction on carsandbids today ( https://carsandbids.com/auctions/rG5RyJqw/2011-bmw-1m ) and found this interesting comment from the seller regarding an aftermarket rear differential that he had installed:

"These cars were originally shipped with the M variable differential from the E9x M3 with the DCT transmission. The final drive ratio of 3.154:1 was well suited for Autobahn speeds but quite tall for North American roads and speeds,[although the total 369 ft lbs of torque available in boost/passing made up for this gearing ].

This car has a, new in 2020, M variable differential with a final drive ratio of 3.620:1. This is the same final drive ratio as the E46 M3 6 speed manual. Here are some speeds in various gears as per recent speedo and gps test.

2nd gear. 4000 rpm 39 mph/63 kph
3rd gear. 4000 rpm 58 mph/93 kph
4th gear. 3000 rpm 58 mph/93kph 4000 rpm 74 mph/119kph
5th gear. 3000 rpm 67 mph/108kph 4000 rpm 88mph/142kph
6th gear. 3000 rpm 78 mph/126kph 4000 rpm 102mph/165 kph

I have been thrilled with this upgrade. The driver is now able to enjoy using more of the 6 gears more often while accessing the power band sooner for quicker response and acceleration. It is fantastic!"

Just thought I'd toss this info into our 1addicts 1M forum for the 4 original owners left and the other 5 who regularly visit and post.
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      03-21-2024, 12:38 PM   #2
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Interesting, I do not feel like the gearing is tall, probably due to the power band really hitting before redline, but I would have loved to drive this car with the new RD.
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      03-22-2024, 08:27 AM   #3
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very odd someone would want a shorter gearing to their 1M. I don't see the advantage in doing this on a street car given the 1M peak tq comes in very early in the power band. I shift before I even hit redline and rarely bang in every gear at redline because I can no longer feel the car pulling any harder.

Most of the local tracks around here will get you up to 4th gear for a slight moment before you downshift. Sounds like the owner loves to shift more often than others. In hindsight, you can look at this as honing your driving skills perfecting for a heel/toe downshift. lol
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      03-22-2024, 07:46 PM   #4
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Quote:
Originally Posted by E46M3forRay View Post
very odd someone would want a shorter gearing to their 1M. I don't see the advantage in doing this on a street car given the 1M peak tq comes in very early in the power band. I shift before I even hit redline and rarely bang in every gear at redline because I can no longer feel the car pulling any harder.

Most of the local tracks around here will get you up to 4th gear for a slight moment before you downshift. Sounds like the owner loves to shift more often than others. In hindsight, you can look at this as honing your driving skills perfecting for a heel/toe downshift. lol
It's pretty well-known that the N54 tops out at 6k rpm with stock turbos. If you swap to running 295/30R18 rear tires, you're effectively geared to 3.59 and 285/30 is exactly 3.62, with the stock 3.15 differential. The BMW engineers knew what they were doing
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      03-30-2024, 06:07 AM   #5
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I changed to 3,45 with a ZF 008 LSD and I can Tell you the car feels so much better..
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