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Discussion Starter #1
Gang:

A local BMW tune shop can get 3.46 rear ends for around 1900 bucks. I bet if we were to do a "Group Buy" we might be able to get a lower price.

Now they are NOT limited slip. But a good price. And these guys are BMW only nutz :)

Let me know..............
 

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I think that the stock M5 diff is a great choice for best all-around performance. Going to a non-limited-slip w/ a higher ratio seems to be a double disadvantage.
 

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Discussion Starter #3
I respectfully disagree.

You only really loose top end speed. But i was just throwing this out there if you guys were interested. :)
 

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Can Quaife LSD be put in these?? Are these diffs from old model BMWs??


Thx,

Mike

btw, Koala Motorsports is coming out out with 3.45 LSD (Quaife) in about 4 months for under 3 grand. It may be worth waiting

Mike
 

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Without trying to sound ignorant: What exactly does the limited slip do in our cars?

Is that the DSC? That sounds like a darn good price for the diff.
 

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You do NOT want to install a differential in your M5 that does not have a limited slip!

First of all, you're going to be spinning the inside (unloaded) rear wheel whenever you accelerate out of a turn. Your DSC will become MUCH more aggressive at cutting power to the motor because that one driven wheel will slip more frequently. Acceleration will become a herky-jerky experience. Especally since the higher numerical ratio will make it even easier to spin the rear wheels.

If you thought the M5 was bad in snow now, just wait until you install a pegleg (non-limited slip) differential!! It will become a patheric, worthless hill climber in the slightest snowfall.

In a discussion I had with the 5-series product manager at BMWNA Headquarters, he explained that the DSC was programmed differently in the M5 to compensate for the effect of the limited slip. I don't know what the effect would be on the DSC to switch to a pegleg differential.

Having made the transition from a 2001 540i with pegleg differential by installing an M5 diff, driveshaft, and halfshafts, I can tell you that the limited slip makes a HUGE difference to the personality of the car. You would simply have to be nuts to want to take your M5 and convert it to a pegleg diff.
 

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Here is the answer I received about Quaifes:

We currently offer 2.65, 2.81, 2.93, 3.15, 3.23, 3.45, 3.64, 3.73 and 3.91 for
the E39 M5.

Speedo does not have to be touched, as the vehicle speed signal is picked up
from a wheel speed sensor, located after the differential.

Thanks.

-----------------------------------------------------
BMW Special Tool Rentals
Pay per incident tech support
-----------------------------------------------------
Brett Anderson
KMS
www.koalamotorsport.com
 

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David Z,

Didn't you have a Quaife in one of your cars? What do you think about it vs. Dinan or our stock diffs?

Also, with more gear choices, how can one figure out if a lower (higher number) ratio is better?
 

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Can someone explain what the difference is between Quiafe and stock? :confused:


I don't quite understand what he means:confused:


Price is $3150, you need to do nothing other than add oil.

Note that for $150 more than Dinan's clutch style LSD price, you're getting a
$1200 Quaife unit installed.

Can do what Dinan does, for $2250.

Core charge of $1500 applies. 100% refunded on return of your original M5 diff
in our crate.
 

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01M5 said:
David Z,

Didn't you have a Quaife in one of your cars? What do you think about it vs. Dinan or our stock diffs?

Also, with more gear choices, how can one figure out if a lower (higher number) ratio is better?
I've never had a Quaife. I did have a Torsen in my 3rd Gen RX-7 twin-turbo and I really liked it. I'm toying with the idea of having a Torsen LSD made up for my 1996 Impala SS because my stock clutch-pack LSD has given up the ghost, making it harder for me to embarrass the locals at the BMW club autocrosses. (My Impala is not very stock in the brakes and suspension department, although it looks stock.)

The Quaife, like the Torsen, is a torque sensing, gear driven differential with no clutch plates to wear out and no requirement for special friction modifiers in the differential fluid. There are some Torsen differentials that also have clutch plates to allow for some preload, but that's typically for race applications only. There is an upper limit to the horsepower capability of a Torsen that isn't much more than 400 hp and the same may be true of the Quaife.

It's hard to say, with certainty, which numerical final drive ratio is "better" than another. As you go higher, you will accelerate quicker (to a point) but you will also be running at a higher RPM for any given speed in top gear. For drag racers, you may find that going too high results in having to make an extra shift before you hit the end of the 1/4 mile. And road racers may find that one set of gears is ideal for Lime Rock, but not so good for Watkins Glenn. Nothing is free and, with gear swaps, you are giving up something in return for something else.
 

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i'm impressed that these guys have all the ratios available, but slightly concerned that they are really M5 gears which are not the same as the other e39 rear ends

i love my Dinan 3.45. i ran a modified e28 with 3.62 rear end for many years and loved it, and sometimes wondered if i shouldn't have gone for the 3.73

before making a decision you should do the numbers -- you won't get to 60 in 2nd with a 3.62 even with a Dinan chip although you can stay in 4th for 1/4 mile with the 3.62 but maybe not with the 3.73, and not with the 3.91

with the 3.45, i hit the rev limiter (Dinan modified) before turn 1A and before 11 at Sears Point -- but it was so close that i backed off rather than going to 4th and back down -- haven't encountered similar situations at Laguna or Thunderhill

i think, given the weight of the car that the 3.45 is very worthwhile and wouldn't argue with a 3.62 if you're willing to give up some gas mileage and cruising sound level -- the 3.73 or 3.91 need real research into your use

Steve Dinan doesn't like the Quaife or Torsen, having to do, as i recall, with the "fuzzy" way that they engage compared to clutch-pack limited-slips -- don't know if this would have any interaction with the M5 computer (which is going to be turned off when you're really working the diff anyhow)
 

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Tim W said:
I respectfully disagree.
Going to a non limited slip makes no sense at all to me, unless you like spinning one wheel all day long. Increasing the leverage of the diff, by changing the ratio, would only exaggerate that problem. That's why I said it was a double-disadvantage.

Being an engineer in a world of enthusiasts means that I'm used to people disagreeing with me. :crying2:
 

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I would definitely agree with Dave Z. here and would NOT recommend that you guys put in a non-LSD to replace the factory unit. My 540 has the open diff (pegleg) and I have been looking into upgrading it to have limited-slip. After helping Dave with his M5 diff/driveshaft/halfshafts, I decided to have a custom differential with a Quaife ATB made by VAC Motorsports. I came to this decision having driven the three current setups possible for the E39:
1) Stick with open-diff.
2) Install M5 rear-end (diff, driveshaft, and halfshafts)
3) Make new diff with new gears (3.15) and Quaife ATB

I have driven all three of these setups on the street and on the track. Who knows how the Quaife unit works, but it WORKS!! It is awesome on the track. The car just feels very planted on the track, especially in turns with the power on the throttle. It is extremely stable, quiet, and smooth. I did not notice it working, but I did notice the results. I was able to drive very quickly on the track, that is until my friend totalled his car the next day.

In terms of gearing, why would you guys want to go so low? 3.64 is pretty low for a car like the E39. These are great GT cars and I would imagine that this change would really only be benificial if you are really planning on driving the car on a specific track. On the street, you would most likely (I haven't crunched the numbers) have to shift to 3rd before 60. You will find that around town, you would either be shifting a lot more, or that you will be keeping it in a higher gear and really stressing the engine driving it at lower engine speeds. Yeah, torque is multiplied as you lower the final drive ratio, but at what expense?

When I was deciding whether or not to have the new diff built with 2.81 or 3.15, I considered the tracks and streets that I was driving. When would I need to shift with the 3.15? On the track, I was going to have to do a few 3-4-3 shifts at Watkins Glen with the new gearing, but the added acceleration out of the corners would negate any time lost to up/down shifting.

Unfortunately all of my efforts and research into the new diff is now meaningless to me, since I am selling the 540 and getting an '03 E46 M3. And that car has a new variable lockup LSD. (0-100% lockup!!!! vs. 0-25% on the current clutch-pack LSD on the M cars. including the E39 M5)
 

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HaroldC said:

In terms of gearing, why would you guys want to go so low? 3.64 is pretty low for a car like the E39.
That's easy. Many believe, based apparently on non-technical reasons, that the car goes faster if you lower (increase the ratio of) the gearing.
 
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