what i have is a 657 case has anyone heard of it? i was told it was a early 60s . i had a 489 323 and i replaced it with this 410 657 case and did not realize that there was no thrust washer now i cant get axle adj. what type of posi is this unit?
Yes the 657 is the earlier version of the 741, they're identical. As far as which type of """"SURE GRIP"""" is in the unit, how about you tell us cuss it could be either cone of clutch. If it is a clutch type there are 2 thrust spacers that can installed without disassembling the entire diff case.