BMW Motorsport Limited Slip unit for sale

[jpjp]

BIMMERPOST / Classifieds

Asking Price:

None

Item Interest

This is a BMW Motorsport Limited Slip unit which runs over $3,860.00 new.
Ramps are approximately 30/30. It will fit e46 and E90, E92 M3, or any diff with 8 bolts retaining the side bearing.

SOLD!!

[jpjp]

Price drop to $2,200.00

[adc]

Novice here in terms of limited slips, but could you explain the difference between this and the stock M3 diff?

(and free bump for an interesting item).

[jpjp]

Originally Posted by adc

Novice here in terms of limited slips, but could you explain the difference between this and the stock M3 diff?

(and free bump for an interesting item).

I am not very familiar with the new design that comes in the E90 M3 vehicles which I think is electronically controlled but here is what I know about the differences:

Limited slip units are the helical gear type (e.g.,Quaife, Torsen) or the friction disc type units. The lesser of these two types - helical gear - have only dynamic lock capabilities (at a pre-determined, unmodifiable rate). (dynamic lock is generated BEFORE there is a need for it) Without static lock, if both rear wheels are not getting comparable traction, the instant one wheel slips, the differential will behave like an open (non-limited slip) unit . All torque will be diverted to the slipping wheel.

I am not a master on the ramps verses non ramps but I know it works in a way that as you push the car harder, the ramps engage deeper which increase the lock between the two wheel. My BMW motorsport unit contains double the friction plates & less angle on the ramps. 75% Lock up. It provides on-demand lock (static/dynamic) in all driving situations and
either statically or dynamically generates more lock for any given driving situation to prevent any wheel slippage before it can even occur.

One of the BIGGEST differences you will see with the various systems is that some units will actually let a wheel spin if you unlevel the car such as in an off camber turn. Ideally you want both wheels to plant and maintain forward momentum so you don't have to wait for the car to settle to regain traction. Some will send power to the wheel that has the most slip rather than grip. If you have ever tracked your car, you would understand how annoying it is to spin a wheel in the air and have to wait.

To understand lockup.. 25, 40, or 75 percent of the torque applied to the faster wheel is applied to the slower wheel, effectively 'limiting slip'. I think most BMW LSDs are 25%.

Good link: http://www.bmwtips.com/tipsntricks/t...fferential.htm

[jpjp]

feel free to make an offer

jp

[jpjp]

bump

[Dave07997S]

Originally Posted by adc

Novice here in terms of limited slips, but could you explain the difference between this and the stock M3 diff?

(and free bump for an interesting item).

JP gave a good explanation, but the issue of the OEM variable lock is its pump driven while the motorsport diffy is mechanical lock up and different ramp speeds dictate the speed and when it locks up.

The OEM M Variable is fine for the street and occasional track use but you will wear it out if you track the car regularly.

Dave