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Discussion Starter · #1 ·
Heard the the euro M5 has a 3.15 ratio vs U.S 2.81. Can some of my fellow euro M5er help me confirm this? want to change my gear box and was hopeing that this was true.So I can just buy the euro gear box and bolt it on mine U.S M5. How about the Z8?does anyone know if that will fit?I know they have the ratio at 3.81!!!! wow
thanks in advance
jim


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I have some questions concerning the rear axle ratio myself. According to my American brochure and the BMW-USA web page the american version also has a 3.15. I believe most of the car magazines are wrong. It would not make sense to use the 2.81 with the increased rev limit of the M5 over the 540. I have also verified this by calculation. I calculated the top speed in each gear based on a 3.15 axle ratio and I have verified it in the car. So I am 99% sure we have a 3.15 ratio. The US car and Euro differ mainly in the brake rotors and some minor options not related to performance.

However, you still can swap rear axle ratios keeping in mind that what you will be gaining in 1/4 mile times will tenths of second. Say from 13.2 to 13.0.
 

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I'm a little new to changing gear ratios and stuff like that. How would you go about doing it? I've very seldom seen tuners selling gearboxes by themselves.
Terence
 

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Discussion Starter · #4 ·
your right jeff I just checked out the brochure and it does say 3.15 for it ratio.
what about the Z8's gear box??would that make the M5 more snappy??
 

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North American Z8 brochure states that the final drive in it is also the 3.15. Don't bother swapping them.
 

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You can still swap your gear ratios by changing the ring and pinion set, but BMW no longer sells these seperately. You have to buy a whole new differential. I am not sure of the details. A good option may be a Quaife differential. Check with them or a good performance tuner.The cost will be two to three thousand dollars.
 

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Originally posted by Jeff L:
You can still swap your gear ratios by changing the ring and pinion set, but BMW no longer sells these seperately. You have to buy a whole new differential. I am not sure of the details. A good option may be a Quaife differential. Check with them or a good performance tuner.The cost will be two to three thousand dollars.

If you intend to alter the drivetrain, don't bother going with a BMW setup, go with the above mentioned Quaife diff, as I have heard nothing but praise for their products.
 
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