i have an 80 Z/28 and my build sheet has the 4 speed rpo-m21 left overs from 79 then?Gary S said:That number probably doesn't exist. In 1980, Chevy coded all Camaro 4 speed trannys as RPO-MM4. That included Z28s, but they don't break the numbers down any farther than that.
In 1979, The Borg Warner used in the Z28 was a closer ratio tranny so Chevy coded it RPO-M21 and separate numbers exist so it can be identified from the wider ratio Saginaw trannys offered in other Camaros.
For 1980, the Z28 still got a Borg Warner, but it was the wider ratio version to handle the higher geared rear ends used in 1980 to help fuel mileage. Because Chevy chose to call both the Z28s Borg Warner and the other Camaros Saginaws wide ratio trannys, they decided to lump them together under RPO-MM4 instead of separating them out on the list.
RICARDO1969 said:i have an 80 Z/28 and my build sheet has the 4 speed rpo-m21 left overs from 79 then?