E46 M3 CSL Diff Rebuild options

Introduction:

Over time the E46 M3 CSL Differentials have worn (as all mechanical components do), and some have developed the infamous 'M Clunk'.

This 'wear' in the Differential comes from a mixture of some or all of these problems:
1. Poor maintenance (lack of oil change).
2. Excessive back-lash (usually introduced during the Pinion Input Oil Seal change).
3. GKN 1st generation LSD Cluster Play (seen at the right hand side Output Flange).

BMW say these Diff's are 'sealed for life' and they offer no spare parts for the internals.


Rebuild standards:

These Diff's are perfectly rebuildable and we carry out the following items on every build.

All E46 M3 CSL Diff Rebuilds come with the following:

  • Strip down and chemical clean of components.
  • Corrosion removal & treatment of Iron Diff Casing.
  • Painting (Black) of Diff Casing and associated external parts.
  • Supply & installation of all New Bearings for Input & Outputs.
  • Supply & installation of New Crush Sleeve.
  • Professional assembly of entire unit especially backlash and preload.
  • Supply & installation of New Oil Seals for Input & Outputs.
  • Supply & installation of New Diff Rear Aluminium Cover.
  • Supply & installation of New Diff Oil.


Option 1: (Currently not available).


Option 2:
OEM Rebuild as per list above 
PLUS New Clutch Packs and OEM LSD rebuilt too (required to eradicate Clunking)
£1,925.

Option 3:
OEM Rebuild as per list above 
PLUS New Wavetrac Limited Slip Diff (LSD)
PLUS E34 M5 Output Flange Pair (required when fitting Wavetrac)
£3,205.


Ratio change:

The M3 CSL left the factory with a 3.62 Final Drive Gear Set inside the Differential.
Being the flagship M3 model and aiming itself firmly towards the performance orientated owner, some felt it should have come with a shorter ratio final drive.
However, all E46 M3 CSL's have the standard E46 M3 3.62 ratio.

Luckily, BMW Motorsport came up with a different final drive gear sets for their racing program which happen to fit inside the E46 M3 CSL's 'Large Case 210 Diff'.
Amazingly, still in 2020, BMW Motorsport are selling these Motorsport Gear Sets - but we don't know how long for. It might be just selling off old stock - who knows?
1 favoured ratio (3.91) has already been discontinued and is NLA (no longer available).

These are the Gear Sets which BMW Motorsport produced.
Some are currently still available - but that could change at any time:

  • 3.91 - No Longer Available.
  • 4.10 - Available.
  • 4.44 - Limited Availability.
(Although 3.91 is now no longer available, there are limited options to use a 3.85).

Here's our take on the ratio's and their perceived usage in the real world:
  • 3.62 (OEM) Fitted as standard to all E46 M3 CSL's
  • 3.91 (BMW Motorsport) Improved acceleration. Aimed at Fast Road Drivers.
  • 4.10 (Motorsport) Further improved acceleration. Aimed at Fast Road / Track Drivers.
  • 4.44 (Motorsport) Heightens acceleration experience. Aimed at Track / Race Drivers.
You are able to take advantage of these 'still available' BMW Motorsport Crown Wheel & Pinion 'Gear Sets' as we are able to purchase them directly and supply them either on their own here or combined with a Diff Rebuild below:

Option 4: (Currently not available).


Option 5:
OEM Rebuild as per list above 
PLUS New Clutch Packs and OEM LSD rebuilt too (required to eradicate Clunking)
But including using a BMW Motorsport Gear Set like 3.85, 4.10, 4.44 ratio).
£2,895.

Option 6:
OEM Rebuild as per list above 
PLUS New Wavetrac Limited Slip Diff (LSD)
PLUS E34 M5 Output Flange Pair (required when fitting Wavetrac)
But including using a BMW Motorsport Gear Set like 3.85, 4.10, 4.44 ratio).
£4,175.


All our prices include Labour, and VAT.

This is an exchange program where we specially build you a Diff to whichever spec you choose, before your vehicle arrives with us.
We then keep your current Diff which goes back into our exchange program.
Alternatively, you're welcome to pay a £500 surcharge to have your old Diff returned to you.

We require a £1,000 deposit to book in for any of our Diff rebuild options.

If you would like to discuss Diff Rebuild options, or make a booking for this service, please Contact us and we'll be more than happy to help you.