Hello everyone,
I've been hearing that there was a period where the E34 M5 was offered with a lower (3.91 versus 3.73) rear end gear ratio and that the cut off date was around 04/91. My 1991 M5 has a production date of 04/91, so how do I know what I have? Is there any way I can tell from the RPM/MPH ratio of certain gears? Currently, It looks like it tops out (7250RPM) in 3rd at about 100-102MPH and 4th at 140MPH, but these reading are all from the stock speedo. Can anyone advise me on this matter?
I too would be interested to know if this is true and how to tell.
I have a UK 1990 car, so does this mean I have a lower ratio?
Am I right in thinking that a "3.91" ratio mean the propshaft and therefore differential input rotates 3.91 times for every one rotation of the output driveshaft and therefore rear wheel?
Does this mean that the 3.91 should out-accelerate a 3.73, (at least to the 2nd gear artificial benchmark of 60mph) at the expense of lower top speed and higher revs per mph at cruise speed so worse mileage?
Does this explain all the magazines getting from 6.0 to 6.4 0-60 times when I look back over the reprints of car reviews ?
Or am I completely wrong :p , and its actually the other way around ?
Ivan
__________________
"Never enter Karussell when on the brakes! I have gone round there on the roof, I know what I'm talking about." ~ Sabine Schmitz
You are right about the rear end gear ratios and how they are figured. Basically, it's the ratio between the ring and pinion gear in the rear diff. The higher the ratio, the more RPM/MPH, which equals faster accel., unless you have way too much power. But, yes, the expense is lower top speed and worse gas mileage.
KKelly responded to a post a did about a week ago. If you read this (KKelly), it seemed you knew a little more about this. Please comment. As for you, Ivan, I'm sorry to inform you that I think the lower rear end gears were only for the U.S. market cars. I believe I read that somewhere, but I might be wrong. Double check. If you are not a top end speed freak, but rather a tight-twisty-road-lets-whip-the-rear-end-out-and-have-some-fun kind of guy, then you can certainly get the gears from a dealer. Let me know if you can't get the part number, as I have a buddy at a dealer that might be able to look it up for me. The cool thing is that our cars are supposed to get the speedo read from the front ABS sensors, so changing the rear end gears won't throw off your speedo.
MikeK-
I thought they were supposed to get the reading from the front ABS sensor, or at least so I was told. I guess I'll find out pretty soon here when I take my car in for a dyno run. If the speedo shows any speed, then it's off of the rear somewhere (either diff. or ABS sensor). I'll let you guys know when I dyno the car.
My 535i has a sensor that is coloured yellow and clips on, on the right hand side rear of the diff.
It is near the fuel filter.
Well, the 535i is the donor car that BMW give to Motorsport to breathe on to make an M5, but I see no reason why they would change this system to a ABS sensor system.
Unless the diff is different ? I haven`t checked.
My guess would be the diff sensor.
Has anyone got a 100% definate answer?
__________________
"Never enter Karussell when on the brakes! I have gone round there on the roof, I know what I'm talking about." ~ Sabine Schmitz
Ivan-
This coming weekend I'll be changing the reverse light sensor on the transmission, so while I'm under the car I'll check the diff. for any sensors. I see the logic behind the 535i/M5 comparison, but I would not be surprised if it was different. They changed a lot of things on the car, not just motor and suspension. I guess I could always ask my buddy at the BMW dealership, but that would take some of the fun out of it.
Mike K-
The 328i is a great car. It doesn't quite have as much power as the M5, but it is a much smoother engine. But as far as handling goes, it is a lighter car and therefore much more responsive on tight twisty roads. I've done a few things to the suspension to stiff it up, so that helps it out too. My wife actually drives the car every day for work and now that I have the M5, I don't get to play in it any more. But I do have to admit that I like the M5 a little better, but that also has a lot to do with that I like fixing cars and personalizing them and my wife won't let me play too much with the 328i. Are you looking to buy one or are you just curious?
Hi Nene,
I have been considering buying a 328i sport for everyday use. This is so that my M5 does not end up with a monster mileage from everyday use. I have never driven one though..yet!! but i believe they are almost as quick as an E34 M5 3.6.
Rear end gears
But I do have to admit that I like the M5 a little better, but that also has a lot to do with that I like fixing cars and personalizing them and my wife won't let me play too much with the 328i. Are you looking to buy one or are you just curious?
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