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New! MM Technical Services: MM’s Engineering Team will provide setup recommendations specifically tailored for your Mustang. Get help choosing options for a Maximum Grip Box, deciding on coil-over spring rates, selecting a brake master cylinder, and advice on converting your Fox to Hydroboost.

New! Swapping a Coyote into a Fox Mustang? MM's Hydroboost Conversion Kits allow easy installation of a 1996-2004 Mustang Hydroboost power brake assist unit into a 1979-1993 Mustang.

New! Swapping an IRS into your Fox Mustang? MM makes it easier with a brake line kit made just for this conversion. Bolts-in, with no cutting or flaring of brake lines. Designed to fit standard IRS brake hoses.

New! MM now offers a tool for the giant nut securing a Mustang Hydroboost. This MM socket fits the 1-7/8" nut holding the Hydroboost to the firewall mount. Required when changing a Hydroboost unit.

New! MM's billet aluminum Pedal Box Spacer for Fox Mustangs. Replace the breakage-prone OEM plastic spacer when converting to manual brakes or Hydroboost.

Canadians! Please read the latest about ordering from Canada/shipping to Canada.

We've posted the parts list and link to the video of MM's Mustang in /DRIVE Tuner car Shootout

IRS rear differential mount, urethane, with tool, 1999-04 Cobra
Actual product may differ from photo.


  • Item # MMIRSB-46
  • Manufacturer: Maximum Motorsports


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Urethane IRS Differential Rear Mount Kit with tool, 1999-04 Cobra

Reduce wheel hop by installing stiffer differential mounting bushings. MM offers two types of differential bushings, urethane and aluminum. The urethane bushings are much stiffer than the original rubber, yet are still compliant enough to dampen NVH (Noise, Vibration and Harshness). The aluminum bushings allow no deflection at all, and therefore do more to reduce wheel hop. The aluminum bushings are designed to provide adjustment of the pinion angle. Properly setting the pinion angle helps keep driveline vibrations to a minimum.

Unlike many others who offer only the front differential bushings, Maximum Motorsports took the time and effort to actually analyze the IRS system. The MM Engineering Team realized that all of the differential bushings must be replaced as a set. The complete set includes the two front bushings and the essential single rear bushing. If only the front bushings are replaced, and the original rubber rear bushing is left in place, a mismatch will be created in the stiffness of the bushing materials. The more rigid front bushings will deflect less, while the remaining rubber rear bushing will still deflect as much as ever. This in turn will increase the stress on the aluminum front mounting ears of the differential housing. The increased stress can lead to fatigue and stress cracking of the aluminum differential housing. Wheel hop will still be prevalent because the rubber rear bushing will deflect and allow the differential to flop around.

If you had previously purchased a front differential bushing (from somebody other than us!), we offer the rear bushing kit with our removal tool to remove the stock rubber bushing from the factory mount. This kit is designed to prevent potential problems or damage to the differential associated with only having stiffer bushings at one end of the differential.