Some BMW models have the factory ring gear welded to the factory differential (aka center section). This kit includes labor to machine the ring gear and an ARP ring gear bolt kit. Your stock rear end would need to be sent to us for machining service. Please drain the gear oil and remove drive flanges before shipping. Once the ring gear is machined we install the Wavetrac differential (sold separately) into the rear end with proper backlash specifications.

Lead time for machining service 4 weeks.