Track days are hard on a G8X rear end. The differential moves on its factory mounts, the oil gets hot lap after lap, and exhaust heat cooks the rear CV boots until they crack and lose grease. The MMX Performance Ultimate Track Differential Kit takes on all three at once for the G80 M3, G82 M4 and G87 M2.
It is MMX's complete rear differential package in one box: the four-point mounting system, a high-capacity baffled differential sump and a pair of output shaft heat shields. It fits RWD and xDrive cars and installs at factory differential height or raised +10mm for lowered cars.
What the Ultimate Track Differential Kit Covers
Mounting and geometry. The same system as the MMX 4-Point Differential Lift Kit: a billet front differential cradle (MMR55-1604), the dual differential mount (MMR55-1606) at the secondary bush location BMW leaves empty, and two raised poly bushes (MMR55-1605). At factory height it cuts differential movement under load. In the +10mm position it corrects the driveshaft angles that lowering creates, reducing heat and wear at the CV joints and axle shafts.
Oil capacity and cooling. The MMX high-capacity baffled differential sump (MMR55-1600) replaces the factory sump on the factory mounting points. Machined from 6061-T6 billet aluminum, it adds up to 2 liters (2.1 quarts) of differential oil capacity. An internal windage tray keeps the gears and pinion lubricated while reducing drag, internal and external fins add cooling surface, and an extra -8AN port with an M22 to -8AN adapter lets you plumb in an external differential cooler. The dual differential mount bolts straight to the sump.
CV boot protection. The MMX rear differential output shaft heat shield set (MMR55-1607) puts a pair of aluminum shields between the exhaust and the rear output shaft CV boots. Each has a polished heat-reflective face toward the exhaust and a black anodized outer face, and the set works with factory and aftermarket exhausts.
What's Included
- 1 x MMX front differential lift mount / cradle (MMR55-1604)
- 1 x MMX G8X dual differential mount (MMR55-1606) with mounting hardware
- 2 x MMX rear differential raised poly bush (MMR55-1605)
- 1 x MMX high-capacity baffled differential sump (MMR55-1600) with windage tray, magnetic drain plug and seal, fill plug and seal, M22 to -8AN adapter and mounting hardware
- 1 x MMX rear differential output shaft heat shield set (MMR55-1607) with mounting hardware
- Optional: BMW L-5970 liquid sealant, 50ml (83190404517), when selected
Key Features
- Complete package: four-point differential mounting, high-capacity sump and output shaft heat shields
- Installs at factory differential height or raised +10mm
- Up to 2 liters (2.1 quarts) of additional differential oil capacity
- Internal windage tray with internal and external cooling fins
- -8AN port with M22 to -8AN adapter for an external differential cooler
- Heat shields protect the rear output shaft CV boots from exhaust heat
- Cradle, dual mount and sump machined from 6061-T6 billet aluminum
- Direct fit with no modification required
- Fits RWD and xDrive models
- Part number: MMR55-0003 (MMR55-0003-RTV with BMW sealant)
Vehicle Fitment
Fits the following S58-powered models, RWD and xDrive:
- BMW G80 M3 Sedan (2021-2026)
- BMW G82 M4 Coupe (2021-2026)
- BMW G83 M4 Convertible (2022-2026)
- BMW G87 M2 (2023-2026)
- BMW G81 M3 Touring (2023-2026, not sold in the US)
Installation Notes
Professional installation is recommended. The sump swap means draining and refilling the differential oil, and the cradle and both rear bushes must be set to the same height position.
- Raise the car level and support the rear differential.
- Drain the differential oil and remove the factory sump.
- Remove the factory front differential mount and rear differential bush.
- Choose factory height or +10mm and set the cradle and both rear bushes to the same position.
- Install the MMX sump, cradle, dual mount, bushes and heat shields, and torque the hardware to BMW specification.
- Refill the differential with the correct oil and check for leaks.
