Got an 8 3/4” Mopar open gears rear & housing assy. Thinking from ‘65-‘69. Question, will all the 8 3/4” housings it take a posi unit or is there a chance it won’t fit. Read some where there were different housings for the ones with Posi traction?
What do you mean by housing? The housing and carrier (center section) are the same, the case is different (where the ring gear bolts).
Chrysler called them “sure grip” units and there are three different pots. The casting numbers will end in 741, 742 or 489. Each has a different pinion diameter but I’m pretty sure the limited slip units themselves interchange between all 3.
Yup the only difference is the pinion size. Chrysler used cone clutch and clutch pack sure grips, if I were buying a new one I would put a Eaton tru-trac (Torsen) in it.
The motorhead guys are going to tell you the 741 is the weakest of the three because the pinion diameter is the smallest of the 3. Don't let that distract you. Mopar used the 741 in most truck applications in the early years. They are just as tough as the largest diameter 489 pinion.
Like Gene size above, 741 is considered the weakest, but is no slouch. I had a 742 in my Valiant and ran low twelves for more then ten years with slick and a four speed. It survived 6000 rpm launches and never broke. The biggest down side to a 741 is the small number of gear ratios available.
741 case here from a 67 baracuda, holding up great, I have a 489 carrier with 3.23 gears open I have been waiting to have built, but the 741 is still doing great with all the abuse I have been giving it over the years... I will probably just throw a true trac in it and be done and sell the 489 to a muscle car guy.
The Jalopy Journal
