Includes all coil-over conversion parts, except the spring, to install 1 Yellow Series second-generation MM shock, along with an MM Racing Upper Shock Mount, for a coil-over conversion in 1979-2004 Mustang chassis equipped with a solid axle.
Installs 1 Yellow Series 2nd Gen MM shock to an MM Racing Upper Shock Mount in a coil-over conversion:
- Threaded sleeve
 
- Upper spring perch
 
- Lower spring perch with locking screw
 
- Shaft retaining nut
 
- Shock shaft spacers
 
- Circlip to support threaded sleeve
 
- Order 2-1/4" coil-over springs separately.
 
- Fits 1 shock. 2 MMCO-21 kits required per car.
 
Fits
- 1 shock. 2 MMCO-21 kits required per car.
 
- Yellow Series second-generation MM shocks. These shocks are yellow and have a shaft with a 5/8” major diameter. Yellow Series part numbers have this format: MMD-RC0xxxx.
 
- MMSM-12 Racing Upper Shock Mount
 
- MMSM-1, MMSM-3, and MMSM-5 Racing Upper Shock Mounts. Some of the previously installed components of these kits will not be reused.
 
- 1979-2004 Mustang chassis
 
- Solid axle
 
- Coil-over installation only
 
Requires shock-to-axle mounting brackets
- If you have an MM Panhard Bar, the axle mount does double duty as the lower shock mount for the driver side. Only 1 shock-to-axle mounting bracket (MMSM-2) is required for the passenger side.
 
- If you don't have an MM Panhard Bar, you'll need 2 of the shock-to-axle mounting brackets (MMSM-2).
 
Does NOT fit
- Black Series MM shocks, which have a black shock body. Black series requires MMCO-23.
 
- MM 1st Gen yellow shocks having a shaft with a major diameter of 11mm.
 
- Bilstein shocks.
 
- Any shock other than the Yellow Series second-generation MM shocks. Yellow Series part numbers are in this format: MMD-RC0xxxx.
 
- Non-coil-over installation.
 
- Mustangs without MM Racing Upper Shock Mounts.
 
Note
 MMSM-2 does NOT include the lower shock mount bolt (12mm by 70mm, grade 10.9) and matching nut.