# DZeckhausen - M5 Diff question



## O.S. (Jun 22, 2004)

I noticed that you have changed the differential on your 540 to M5 3.15.

I once asked if it was possible but I got responses about it being too cumbersome and required to change the whole lot of other stuff.

Can you tell more about it? Is it a worthwhile change?


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## marinakorp (Oct 3, 2003)

there are other possibilities for getting a 3:15 LSD differential, that does not require changing the driveshaft, etc (the bitch about the M5 from what I remember)


the others only require a DIFF change... which is a lot easier than the above


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## O.S. (Jun 22, 2004)

there is always DINAN - I know 
but if I could pick up a used M5 diff - that's be way cheaper 

BTW Marinakorp - that is quite a GAIN after powerchip LOL sorry 
I heard same story when a 540iT was powerchiped with Gold93 with 0 gain ... was it you on m5board.com?


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## marinakorp (Oct 3, 2003)

Could be... I post in a lot of places under this monikker



well other than DINAN... there are other companies that can offer a LSD for a few K... Quaife, and a few others.


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## bmw540i (Mar 30, 2003)

But isnt it better to get the M5 one because youre not only upgrading the pumpkin youre upgrading the half shafts and a better drive shalfts.


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## DZeckhausen (Mar 11, 2003)

O.S. said:


> I noticed that you have changed the differential on your 540 to M5 3.15.
> 
> I once asked if it was possible but I got responses about it being too cumbersome and required to change the whole lot of other stuff.
> 
> Can you tell more about it? Is it a worthwhile change?


It's one of the best changes I've made to the car. The 3.15 final drive ratio makes the car seem 500 pounds lighter, although I still occasionally try to grab 7th gear on the highway. But it's the limited slip that makes all the difference in being able to launch the car in all kinds of weather. And now I have no trouble making it up the hill to my house in the winter, even when they haven't salted the roads. With the peg-leg diff, I could not make it up the hill without several running starts.

I did need to swap the driveshaft and the halfshafts too. It's not such a bargain if you buy the parts new, but I managed to get everything used (barely) for just $1500 and I did the work myself.


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## O.S. (Jun 22, 2004)

thanx Dave - I will be thinking of M5 diff option too.

There is also Quaife diff that Renn-Sport sells for 1300 and I am trying to figure out what the ratio of that one is.


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## PropellerHead (Jan 3, 2002)

O.S. said:


> thanx Dave - I will be thinking of M5 diff option too.
> 
> There is also Quaife diff that Renn-Sport sells for 1300 and I am trying to figure out what the ratio of that one is.


It is likely the just the dif that they sell for $1300. The GEARS (2.82- or is it .83?, 3.15, 3.45, etc) are whatever you pair the dif with. These are parts internal to what some call the 'pumpkin-' the whole metal unit that goes under the car- which is commonly and incorrectly referred to as the 'dif.'

I had a quiaffe unit paired with my 2.8whatever gears so I could keep my cruise control. On 2000 and newer cars, the cruise doesn't work when paired with 3.15. Unless someone has gotten it to work.


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## O.S. (Jun 22, 2004)

how does the different gear ratio make cruise control stop working?

do you like the Quaife diff? What difference did it make to the car?


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## tsaros (Nov 24, 2003)

DZeckhausen said:


> It's one of the best changes I've made to the car. The 3.15 final drive ratio makes the car seem 500 pounds lighter, although I still occasionally try to grab 7th gear on the highway.


I might be able to get all parts needed for a good price, but im worried about the car running to high revs for my taste on the highway.
How much does your car rev when going 100Mph in 6:th gear?


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## DZeckhausen (Mar 11, 2003)

tsaros said:


> I might be able to get all parts needed for a good price, but im worried about the car running to high revs for my taste on the highway.
> How much does your car rev when going 100Mph in 6:th gear?


It revs 12% more than yours. So whatever RPM you are currently pulling at 100mph, you can multiply by 1.12.


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## tsaros (Nov 24, 2003)

Thank you for your answer, are there any problems with the cruise control in your car with the new diff?


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## DZeckhausen (Mar 11, 2003)

tsaros said:


> Thank you for your answer, are there any problems with the cruise control in your car with the new diff?


Yes. It doesn't work properly anymore. I can set it on the highway and it will hold for a while, then randomly drop off. It's annoying enough that I haven't used the cruise control for at least the last two years.


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