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Re: 3.91 vs 3.72 gear ratio (archive)
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Posted by Ken Little on January 06, 2002 at 05:08:57:

In Reply to: 3.91 vs 3.72 gear ratio posted by mike wong on January 01, 2002 at 17:17:56:

Mike:

I believe the 3.72 was introduced in 5/91 as my mauritius blue car (5/91 build date) has the 3.72. The alpine white car has the 3.91 (1/90 build date). The change was said to be made to increase fuel efficiency, probably the last thing one would worry about when buying a $60K+ car in the early ninety's. The country was in a recession and we had gas rationing here in the bay area. Transmission ratio's remained the same for both differential ratios. I truly have not done a gas mileage comparisson. According to the OBC I average in the low 13's with both cars.

Ken Little

'91 M5 Mauritius Blue
'91 M5 Alpine White


I'm near SF, CA; and have been looking for an M5. I read where the 1991 has a 3.91 rear end compared to the 92-93's 3.72 ratio. Is this correct?
Did BMW keep the transmission ratios the same, too? Assuming tire sizes were the same, why did BMW change the ratio - lower freeway rpms, better mpg, increase top speed?




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