Getting to know my rear end...

67DART340 said
I Just bought a 67 Dart 340 4 speed.. It was stated to have a "posi" 8-3/4 rear... I tried to do a burn out to check the dual traction rear with no noticable 2 tire burn marks, due in part to the type tires and the cold weather... Next step I put the car up on 4 jack stands to check the car out completely for castings, leaks, etc... Well, when I got to the rear, with it in gear, and turning one wheel ccw the other wheel went the other way, cw... Then I put it in neutral and did the same and the other wheel didn't move, but the drive shaft turned... To me this means an "open" non-posi rear... Am I right?.. I inspected the rear and the drums look small... The pumpkin casting numbers were 1820657 which in my books is a 8-3/4 C body rear from 58-64... Is this compatable with later posi's?.. Can I swap out this pumpkin with a later posi?.. Will the axles be a match, etc... How about gear ratio switches?.. The 4 speed is from mid year 76 which I've been told is Over Drive 4 speed tranny... Thanks for any help...

Well, Well Charlie, you got yourself the making of a mystery. Firstly the 657 was the original 8 3/4" later replaced by the 741 in 64, essentially the pumpkins are the same, same bearings and same crown and pinion gear. What seperates the 2 is that the original 657 had their brake drums keyed and lock nuted to the drive axel ends which were also tapered. The 741 got rid of this B.S. and went to flanged end drive axels. I know of an instance where a gentleman took a 657 stamped pumpkin and installed it in the rearend with 741 style drive axels which is hopefully what you got Charlie. The quick and dirty way to find out is remove one of the tires and is the brake drum loose up against the axel flange or is the drum keyed and lock nuted to the end of the axel shaft. Also any posi that's meant for the 741 will fit the 657 carrier.
Also your test of turning the tires says that you've got an open rear, if it was posi both tires would turn in the same direction when you turned one of them.

Terry