Differential – the heart of the drive system

Differential is a key element of the car's drivetrain, which plays an extremely important role. Its task is to enable the wheels of one axle to rotate at different speeds, which is essential when cornering. Thanks to this mechanism, the car maintains optimal traction, stability on the road and even tire wear, which translates into their longer life. In the classic open version, the differential transmits the same torque to both wheels, which in some conditions can limit traction. That is why limited slip differentials (LSD) are becoming increasingly popular, which intelligently redirect power to the wheel with better traction, which significantly improves the car's handling, especially on slippery surfaces or during dynamic driving. This is why sports models of brands such as BMW M or Audi S/RS are equipped with LSD as standard, which increases their performance and road safety.

Symptoms of differential wear

A worn differential makes itself known through characteristic symptoms that the driver should quickly recognize to avoid more serious failures. Most often, there is a loud, increasing noise, resembling a howling, especially in the speed range of 50 to 80 km/h. Additionally, there may be jerks when starting off and unpleasant vibrations in the steering wheel. Ignoring these symptoms may cause serious damage, such as the teeth of the final drive being pulled out, which can lead to the axle being completely blocked and the vehicle immobilized. Early identification of the problem allows for effective repair measures to be taken, which are often less expensive than replacing the entire axle.

When to replace and when to rebuild a differential?

Decision to replace or recondition the differential depends on several factors, including parts availability and the individual needs of the driver. Replacing a used differential is a quick and often cheaper solution, provided that it comes from a reliable source and has the right ratio for the given car, for example 3.46 in a Mercedes W203 differential or 2.47 in a Mercedes W204 W212 differential. Such a purchase allows for a quick return to full vehicle efficiency without a long downtime.

Differential renovation it is, however, profitable when the mechanism has a rare or unusual gear ratio, such as:

• 2.93 in the differential BMW E39 X1 E84 X3 E83 E90 E91
• 2.47 3.38 3.46 3.64 3.73 3.91 4.10 in the BMW E81 E87 E90 E91 differential

or when the owner wants to keep the original drive axle. The cost of regeneration is usually lower than buying a brand new component, and at the same time allows you to maintain the original specification of the car. In both cases, the VIN number of the vehicle plays a key role, which allows for precise matching of spare parts and minimizes the risk of mistakes.

How to safely buy a used differential?

Buying a used differential requires special care to avoid problems and hidden defects. Here are some basic rules:

• Source verification – it is best to choose second-hand parts stores that have a legal disassembly and testing protocol, such as Global Parts. This gives the customer the assurance that the components are verified and come from legal sources.
• Checking the gear ratio – this is stamped on the differential housing or nameplate (e.g. the BMW E46 330d differential has a gear ratio of 2.81; 2.28 or 3.15). The correct gear ratio is crucial for the drive system to function properly.
• Check radial clearance – too much clearance indicates bearing wear, which can lead to more serious failures.
• Assessing the condition of the seals – wet flanges are a signal that the seals are worn and may soon require repair.
• Choosing the right oil – Open axles typically run on 75W-90 oil, while LSD differentials require a higher viscosity oil, e.g. 75W-140.

Global Parts offer – differential immediately and expert support

Global Parts Automotive Store is a place where drivers will find a wide selection of differentials for various car makes and models. The offer includes, among others, BMW E90 differential, E60 differential, as well as: E81, E87, E91, F10, F20, F30, X3 E83; Mercedes W203, W204, W205, W212 W213 Sprinter W906 W907 differential; Audi Quattro Q3, Q5, Q7, S3, RS3; VW 4Motion Tiguan, Touareg and many others. By providing the VIN number, the customer can count on comprehensive service from experts who:

• verify the gear ratio and differential type (open or LSD),
• advise whether the better solution would be to buy a used component or to renovate it,
• they reserve the appropriate part or accept the bridge for regeneration.

Thanks to this, the driver receives a full guarantee, proper adjustment and professional support in the selection of oil and other accessories. The entire process takes place in one place, without the need to search for information on internet forums or auctions, which significantly facilitates and speeds up the repair.

FAQ - drivers' most frequently asked questions

Below you will find a list of the most common questions drivers ask, along with answers prepared by the Global Parts team.

BMW E87 E90 E91 differential howling at 60 km/h – what to do? It will be necessary to rebuild or replace the complete differential.

BMW E60 E61 differential jerks when starting? Typical symptom of worn bearings, the complete differential will need to be replaced or rebuilt.

BMW E87 E90 E91 differential – what oil? Standard oil is 75W-90.

Mercedes W203 differential makes noise when cornering? The most common cause is worn bearings – replacement or purchase of a used bridge is necessary.

Mercedes W202 differential, does it fit W210? Yes, as long as the part number and ratio are the same.

Audi Quattro differential vibrates at low speed? The problem is usually the rear differential bearings; replacement or reconditioning is required.

BMW differential,Audi , Mercedes , Mini – repair or replace? In case of a cracked housing, a used differential is better, in case of noise – bearing regeneration.

Will this differential fit my car? To ensure proper fit, please provide your VIN number.

Has the differential been rebuilt? We sell used and refurbished differentials.

Does LSD improve traction in snow? Yes, LSD redirects torque to the wheel with better traction, making it easier to start on slippery surfaces.

Why is it worth having an efficient differential?

An efficient and regularly serviced differential is an investment that pays off in everyday vehicle use. It reduces tire wear, stabilizes the driving track and reduces fuel consumption, which is confirmed by numerous industry tests. In the event of a failure, simply contact Global Parts , where not only used BMW parts are available , Mercedes , Audi or VW , but also professional assistance in the regeneration of BMW differentials, which allows for a quick and trouble-free return to full functionality of the car.