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E30 Differential Upgrade - Custom Options

Mfg Part #
TMS340133
Turner Part #
T#340133
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Price:
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1924.00
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Product Details

Upgrading or rebuilding the differential is one of the keys to the performance of the E30 325 or E30 M3. The 325e had a very tall 2.79 or 2.93 final drive for fuel economy and because of its low rev limit. The 325i and 325is manual transmission models had a much snappier 3.73 rear end. The M3 came with the shorter 4.10 gearing. For most E30 owners the standard gearing is well-suited for the street. If the shorter 3.73/4.10 gearing is too high for daily driving you can swap to a taller gear for lower revs (better fuel economy, less noise). On the flip side, changing to a shorter gear can work in your favor for acceleration runs or if you find yourself at the wrong RPM for certain tracks. And if you have installed an M50/S50/S52 engine the gearing should be changed as well to make better use of the new torque curve.

Gearing Changes Using a shorter gear ratio (numerically higher) will give you better acceleration but will reduce your top speed. The higher ratio puts you at a higher RPM point for any given speed. This puts you further up in the power band, giving you more torque to the ground. Click the banners below to see how different ratios relate to particular speeds.

Gearing Charts:

E30 M20, Getrag 5-speed manual, 205/50-15" rear tires

(click to expand)

Gear RatioGearSpeedRPM

70 MPH Cruise

3.465th70 MPH2,900 RPM

3.735th70 MPH3,080 RPM

3.915th70 MPH3,250 RPM

4.105th70 MPH3,400 RPM

Theoretical Top Speed With Raised Rev Limit

3.735th154 MPH6,800 RPM

3.915th147 MPH6,800 RPM

4.105th141 MPH6,800 RPM

These are just a range using a stock and a selection of alternative gear ratios. Speeds and RPM will obviously change in between ratios.
Speed in 5th gear at 7000 RPM is for theoretical and comparison purposes only. It doesn't mean that these speeds are actually reachable.

E30 M50, M3 ZF 5-speed manual, 225/50-15" rear tires

(click to expand)

Gear RatioGearSpeedRPM

70 MPH Cruise

3.735th70 MPH3,750 RPM

3.465th70 MPH3,400 RPM

3.255th70 MPH3,250 RPM

Theoretical Top Speed With Raised Rev Limit

3.735th133 MPH7,000 RPM

3.465th144 MPH7,000 RPM

3.255th153 MPH7,000 RPM

These are just a range using a stock and a selection of alternative gear ratios. Speeds and RPM will obviously change in between ratios.
Speed in 5th gear at 7000 RPM is for theoretical and comparison purposes only. It doesn't mean that these speeds are actually reachable.


Limited Slip Options. If you're lucky enough to have an E30 with a factory limited slip differential we don't need to make too many changes. But we will rebuild it for you. If you do not have an LSD already you will want to get one, especially with an M50 swap. Without a limited-slip you're suffering from 'One Tire Fire' - all of your power goes through one wheel. The limited slip will balance the torque through both rear wheels before the one begins to spin (depending on the lock-up you choose). We offer limited-slip options that are similar to the factory 2 or 3 disc limited slip, Quaife helical style (no clutch packs), and OS Giken multi-disc variable LSD that our race team uses.

Core Charge. If we are building a diff from our own stock a refundable core charge will apply until we get your original diff back. You have a maximum of 30 days from the time you receive the diff to send it back us for a refund. There is a $400 charge for a factory LSD diff and a $200 for a factory non-LSD (open) diff. To make the process simple, all custom diff orders are charged $400 and the refund will be based on the diff that you send back. Click here for more detail and explanation of the core charge.

FAQ: For a full FAQ on the custom diff process, click here.

This custom differential fits the following BMWs:
1984-1991 E30 BMW 318i 318is 318ic 325e 325es 325i 325ic 325is M3

​*Please note, if open differential core is returned only $150 if core charge will be refunded* 

Loading Kit Configurator

1924.00
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Kit Configurator

Current Price:
1924.00

Add REM bearing polish?

Add REM ring & pinion polish?

Core Charge

Select your gear ratio:

Select your limited slip option:

Base differential

This Part Fits the Following BMWs

Make Model Submodel Engine
BMW E30 318i M10 1.8L
BMW E30 318i M42 1.8L
BMW E30 318is M42 1.8L
BMW E30 325 M20 2.7L
BMW E30 325e M20 2.7L
BMW E30 325es M20 2.7L
BMW E30 325i M20 2.5L
BMW E30 325is M20 2.5L
BMW E30 M3 S14 2.3L
*The above product applications have been written by Turner Motorsport. All warranties, product application, fitment, and performance are the responsibility of Turner Motorsport. For additional information see the terms of use.
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