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pamato
11-22-2004, 12:31 PM
What is the gear ratio on a sport 2001 540i, 6 speed MT?

What are the advantages on changing the gear ratio? I am a newbie to BMW and cars, so forgive my rookie questions.


Thanks,

Paul

back_mtn_boy
11-22-2004, 12:49 PM
Higher gear ratio = faster acceleration
Lower gear ratio = better gas mileage (maybe)

Of course, YMMV... ;)

cheers - John

pamato
11-22-2004, 02:19 PM
Higher gear ratio = faster acceleration
Lower gear ratio = better gas mileage (maybe)

Of course, YMMV... ;)

cheers - John


How can I find out my gear ratio?

Paul

Steve D
11-22-2004, 02:43 PM
The only gear ratio available is 2.82 for the 6 speed. The Steptronic with sports package came with a 3.15 ratio which you can swap fairly easily. I did the swap and love it. More response and 6th gear is much more useful. My mileage actually went up slightly.

See my swap procedure posted on BMWTips .com for details.

Steve D

Schnell5
11-22-2004, 06:39 PM
The only gear ratio available is 2.82 for the 6 speed. The Steptronic with sports package came with a 3.15 ratio which you can swap fairly easily. I did the swap and love it. More response and 6th gear is much more useful. My mileage actually went up slightly.

See my swap procedure posted on BMWTips .com for details.

Steve D
Are you sure the 3.15 isn't standard with a 540/6? I could swear I recently read it was....

SteveM
11-22-2004, 06:52 PM
Higher gear ratio = faster acceleration
Lower gear ratio = better gas mileage (maybe)

Of course, YMMV... ;)

cheers - John


Also, a higher gear ratio (numerically) means a lower top speed (at redline) and the converse is also true (lower gear ratio = greater top speed).

Steve D
11-22-2004, 08:54 PM
Nope, the only gear ratio available with the 6 speed is the 2.82 at least for 97-02 models. Now I read something about the 3.15 being available in some 2003 540/6sp for the final year only. Can anyone confirm this?

Steve D

pamato
11-23-2004, 07:27 AM
Nope, the only gear ratio available with the 6 speed is the 2.82 at least for 97-02 models. Now I read something about the 3.15 being available in some 2003 540/6sp for the final year only. Can anyone confirm this?

Steve D


I was just checking out the Dinan webpage and it seems to indicate that all sport models have a gear ratio of 3.15, but not the limited slip differential.

My questions is: What is the difference between the Limited Slip Differential and the stock differential?

Paul

Steve D
11-23-2004, 02:50 PM
All auto trani models with the sport package have the 3.15 diff but not the manual 6 speeds. The M5 comes standard with a 3.15 LSD. The LSD is not available in any other E39. Dave Zeckhausen swapped the M5 LSD into a 540 but had to swap the driveshaft and halfshafts as well - big job. Check out his website. You can buy a Quaiffe LSD for the 540 but it runs about $2K.

LSD does mechanically what the DSC does electronically by using clutches in the diff it maintains equal traction to both rear wheels.

Steve D

Tahoe
11-23-2004, 03:12 PM
The above is correct. All auto E39 540s have the 3.15 while all 6 speed models have the 2.82 EXCEPT the 03 M Y which came with the 3.15. My '00 540/6 has a 2.82.

No, and LSD doesn't do the same thing as the DSC but mechanically. DSC reduces engine speed and drive power to the wheels until they get traction. LSD adjusts the bias to the wheel with grip. With one you loose power to the wheels with the other you hook up to the road with all the power you have.

Lscman
11-24-2004, 04:46 AM
The above is correct. All auto E39 540s have the 3.15 while all sport models have the 2.82 EXCEPT the 03 M Y which came with the 3.15. My '00 540/6 has a 2.82.

No, and LSD doesn't do the same thing as the DSC but mechanically. DSC reduces engine speed and drive power to the wheels until they get traction. LSD adjusts the bias to the wheel with grip. With one you loose power to the wheels with the other you hook up to the road with all the power you have.

Actually DSC only reduces power/torque when excessive throttle is applied. In addition, it instantaneously reduces torque applied to the slipping wheel, in an effort to regain traction. This is an excellent method to control grip for typical adverse weather situations.

The limited slip differential (found on various BMW's and most rear wheel drive domestic cars sold since the 1960's) does not dynamically reduce torque applied to the slipping wheel. LSD does not hook to the roadway with all the power you have, as you suggest. Under limited traction conditions, an LSD will uncontrollably slip under hard throttle which requires the driver to use great skill to carefully feather the throttle. DSC does this automatically. In addition, the driver does not have a separate gas pedal or brake pedal for each tire, so he can not transfer power to the wheel with grip. DSC does this automatically too. The maximum LSD torque that reaches the tire with grip is modest, unless it's a noisy race unit with high bias. DSC automatically senses & controls slip by applying the brake to the slipping tire and this dynamically transfers power to the road surface and maximizes traction. LSD units offer static bias which is insensitive to traction available at each wheel. The gear-type ATB differentials actually lose mechanical torque bias capabilities under low traction situations & their static bias is near 0.

Under typical adverse weather conditions, DSC is excellent. Under performance driving conditions on dry pavement, DSC tends to become intrusive by trying to manage (control) all wheelspin under high loading & hard throttle conditions. It's method of applying the brake on the slipping wheel causes the brakes to overheat under sustained hard throttle. Under dry "race" conditions, DSC is typically disabled & a mechanical LSD or ATB differential is preferred.

pamato
11-24-2004, 08:23 AM
Actually DSC only reduces power/torque when excessive throttle is applied. In addition, it instantaneously reduces torque applied to the slipping wheel, in an effort to regain traction. This is an excellent method to control grip for typical adverse weather situations.

The limited slip differential (found on various BMW's and most rear wheel drive domestic cars sold since the 1960's) does not dynamically reduce torque applied to the slipping wheel. LSD does not hook to the roadway with all the power you have, as you suggest. Under limited traction conditions, an LSD will uncontrollably slip under hard throttle which requires the driver to use great skill to carefully feather the throttle. DSC does this automatically. In addition, the driver does not have a separate gas pedal or brake pedal for each tire, so he can not transfer power to the wheel with grip. DSC does this automatically too. The maximum LSD torque that reaches the tire with grip is modest, unless it's a noisy race unit with high bias. DSC automatically senses & controls slip by applying the brake to the slipping tire and this dynamically transfers power to the road surface and maximizes traction. LSD units offer static bias which is insensitive to traction available at each wheel. The gear-type ATB differentials actually lose mechanical torque bias capabilities under low traction situations & their static bias is near 0.

Under typical adverse weather conditions, DSC is excellent. Under performance driving conditions on dry pavement, DSC tends to become intrusive by trying to manage (control) all wheelspin under high loading & hard throttle conditions. It's method of applying the brake on the slipping wheel causes the brakes to overheat under sustained hard throttle. Under dry "race" conditions, DSC is typically disabled & a mechanical LSD or ATB differential is preferred.


So Lscman,

Thanks for the input. It sounds to me as if you wouldn't recommend a LSD unless a person was planning to track the car regularly. I live in Seattle, which has hills and rain, so the DSC sounds beneficial to me here. I am researching future mods for my 540/6 and wanted some info whether this mod, 3.15 LSD, is worthwhile to do in the future.

Would you have it done?


Paul

bmw540i
11-24-2004, 06:22 PM
So Lscman,

Thanks for the input. It sounds to me as if you wouldn't recommend a LSD unless a person was planning to track the car regularly. I live in Seattle, which has hills and rain, so the DSC sounds beneficial to me here. I am researching future mods for my 540/6 and wanted some info whether this mod, 3.15 LSD, is worthwhile to do in the future.

Would you have it done?


Paul
Absoulutely, if you want better handling and a faster car.

Lscman
11-25-2004, 06:42 AM
Absoulutely, if you want better handling and a faster car.

For the record, LSD's degrade handling. The Quaife ATB and other variable torque bias gear diff's tout handling that "almost equals" an open differential. Any piece of hardware that tries to equalize the rotational speed of the rear wheels in hard cornering situations can not & will not improve handling. All it does is introduce doses of unwelcome understeer (during light throttle) or tailwag oversteer (during heavy throttle/wheelspin).

A limited slip differential is helpful under situations that:

1) involve lower speeds combined with max lateral G's or
2) involve maximum acceleration at launch, from a standstill.

I can tell you an LSD will offer no benefit on a 540i, if you're racing at Watkins Glen International or any other high speed track. At speeds over 30 MPH, it is seldom useful. ;)

PropellerHead
11-25-2004, 09:05 AM
I can tell you an LSD will offer no benefit on a 540i, if you're racing at Watkins Glen International or any other high speed track. At speeds over 30 MPH, it is seldom useful. ;)As an owner with a Quiaffe ATB in my 540, I disagree. The whole characteristic of the car changes in any turn at any speed. It is more sure footed, you can apply power sooner, it's just been a great upgrade. The car maintains better control during any straight line situation (like high speed shifting) where traction may be lost. Now, I DO agree- as Lscman says- that in a straight line at any speed, the ATB (or LSD) doesn't do a whole lot for you- Except that you know it's there if you need to quickly turn out of something's way. :)

Lscman
01-10-2005, 09:53 AM
As an owner with a Quiaffe ATB in my 540, I disagree. The whole characteristic of the car changes in any turn at any speed. It is more sure footed, you can apply power sooner, it's just been a great upgrade. The car maintains better control during any straight line situation (like high speed shifting) where traction may be lost. Now, I DO agree- as Lscman says- that in a straight line at any speed, the ATB (or LSD) doesn't do a whole lot for you- Except that you know it's there if you need to quickly turn out of something's way. :)

"any turn at any speed"?? I think you're overselling the benefits of an LSD. What you're essentially claiming is your car was capable of spinning it's inside tire thru turns 3 & 4 at Watkins Glen while traveling at speeds exceeding 100 MPH. No way. My foot is buried in the carpet thru turns 2, 3 and 4 with zero wheelspin. I only find an LSD to be beneficial in low speed 2nd gear pivot turns where wheelspin must be managed thru "throttle modulation or steering". These techniques can compromise corner exit velocity and adversely impact lap times. That said, I am can apply full throttle at the apex in most turns at WGI with zero wheelspin. If the shorter NASCAR course is run, my open diff does not require "wheelspin management" anywhere, except exiting the bus stop. Under this scenerio, the open diff may actually produce better handling and lap times.

At higher speeds, the 540i engine does not have sufficient power to churn the inside tire at WOT. For this reason, an LSD serves no function other than promoting understeer. If you have an M5 engine or supercharger kit, the situation obviously changes. LSD's are crutial in typical ponycars with high power (300+ HP) and poor weight distibution (58/42 or similar). The same can not be said for the 280 HP E39 V8 with it's 52/48 weight bias. The E39 rear end is fairly planted at moderate to high speeds.

Your last comment makes little sense to me. An LSD does not help the driver execute a safe evasive maneuver. A torque bias differential is designed to minimize the speed differential between the right and left side tires. This "feature" does not improve static or transient turning capabilities by any stretch. In fact, the variable bias Quaife was designed to mimic an open diff under no-load turning conditions....but it is surely not superior to an open diff under these circumstances.

dagoo98
01-10-2005, 11:05 AM
It is more sure footed, you can apply power sooner, it's just been a great upgrade. The car maintains better control during any straight line situation (like high speed shifting) where traction may be lost. Now, I DO agree- as Lscman says- that in a straight line at any speed, the ATB (or LSD) doesn't do a whole lot for you

You seem to be contradicting yourself in this statement. First you say the LSD maintains better control in the straight line and you follow that up by saying that in a straight line at any speed the LSD doesn't so a whole lot for you. :confused: :dunno:

PropellerHead
01-12-2005, 08:52 PM
You seem to be contradicting yourself in this statement. First you say the LSD maintains better control in the straight line and you follow that up by saying that in a straight line at any speed the LSD doesn't so a whole lot for you. :confused: :dunno:where traction may be lost. :dunno:
(think shifting quickly and catching 2nd)

PropellerHead
01-12-2005, 08:59 PM
What you're essentially claiming is your car was capable of spinning it's inside tire thru turns 3 & 4 at Watkins Glen while traveling at speeds exceeding 100 MPH.I've never been to Watkins Glen. :dunno:

What I said isThe whole characteristic of the car changes in any turn at any speed.and it does.

edit:
and holy old thread.. d@mn what is that.. 2.. 3 months?