I have a 66 SS that currently has a 1968 12 bolt installed.

Question #1 My understanding this is the 68 carrier is the same as a 66 except the axle's are 1/2" longer and the overall lenght is 1" wider; but the location of the mounting points for the upper and lower control arms and springs are the same as a 66. Is This True?

Question #2 My Chassis & Service Manuel say the upper control arm bushing are not the same as the lower control arm bushing; But NPD, Year -1, OPG, etc, catalogs seems to indicate they are the same. What's the truth.

Question #3 Also the catalogs indicate the lower control arms are the same for years 64-72;but the upper arms are different for 64-67 and 68-72.
So what I am wondering is if the upper control arms of a 66 will fit properly onto a 68 carrier? That's the situation now; but I am wondering if I should look for a 66 or 67 carrier.

#1 is true...

If you had both rearends (1966 and 1968, or early and late), you could see the distance between the brake backing plate and the lower control arm bracket are different, with the early rears having much less room (about 1/2") there... So the axle, axle tube and brakeline are different, but everything else is (essentially) the same... The spring pads are different(same location though), but just use springs for your chassis (1966) and you should be fine...

#2, The Truth? You can't handle the truth... smile.gif Sorry... Perhaps "factory" pieces were different, but having replaced many bushings, the replacements are the same size and work fine... I think 1964 Rearends had something different about the upper "ears", but 65-72 are virtually identical... There is a step in the bushing "can" (at least on the replacements I have seen), so maybe thats how the replacements can be used for both...

#3 Due to FRAME differences, the Upper Control Arms for 1968-1972 Chevelles are different from 1965-1967(and the El Camino from those years might also differ from the coupes?). The 1965-1967 upper arms are all the same regardless of model (1964 might differ because of the previously mentioned "ears"... The lower arms for all years are the same...

I have swapped many later 12-bolts into 1966 Chevelles, and never had a problem. Is it worth finding a 65-67 rearend? Thats up to you...

#3 the upper control arm lengths are different. If you put the later ones, on the earlier rear end or vica versa, the pinion angle will be wrong.

#2.. even the chevy parts catalog listed 2 different part numbers. I assumed the only difference is the stiffness of the rubber. I just used the universal Moog replacement.


Rene
66_Malibu