# Welding a differential

The very purpose of a differential is to allow each rear wheel to turn at different speed, such as during cornering. Limited Slip Differentials, often referred to as Posi (which is a GM trademark name for LSD), are used to limit wheel spin but still allow the wheels to turn at different speeds during cornering.
Welding a differential will force the wheels to rotate at the same speed. This is a race trick and has no place on a street car. A car with a welded differential becomes much harder to control under anything but race conditions, it makes the car very uncomfortable to drive at slow speeds, and can cause an inexperienced driver to lose control of the car during cornering. It is not recommended for anything other than race cars that are never driven on the road.
To weld a differential, drain the oil, remove the rear cover and weld the spider gears. This should only be done with an open (non LSD) unit as an LSD cluster has no access for welding.
Rotate the differential until the spider gears are visible through the openings and weld the 4 gears together. |
An example of a welded set of gears. Take care not to allow weld splatter to damage the splines in the outer gears. |

### Torques :

Differential cover mount to body | : | 87 Nm (63 ft lbs.) |
Cover bolts | : | 44 Nm (32 ft lbs.) |

E30 M3 Repair Manual V2.7. Copyright ©1999-2001 Koala Motorsport & Brett Anderson