The frame is painted and it's time to start building back up. I want to replace the 2.56 gear with a 3.42 setup with posi. We verified the rear is a 8.5 with the help of all you members. I have a some info and pricing, but need some feedback on this conversion. I don't know much about rear ends and any info would help. Does the carrier need replacing, install kits, right gear, posi etc. Maybe someone has the parts necessary collecting dust somewhere they would like to sell. The 455 is going through a mild buildup from stock, nothing to radical if this helps at all.
decent gears: summit nice gears: motive gear really nice gears: Richmond The 410408 posi carrier is the 3 series that will hold your 3.42 gears without a spacer. The 410409 posi carrier is the two series carrier that will hold your 3.42s with the use of a spacer (Mr Gasket 908A). I have also used an Auburn/strange engineering 3 series posi unit with very good results. I have used install/bearing kits from summit and RAtech with very good results. Setting the gears up is a precision job requiring measuring tools and shims. Do you know someone to do it for you or plan on doing it yourself? The easiest way is to find the posi axle you want somewhere as a complete assembly then swap it in.
I know it is relatively minor, but you need to also change the speedometer pencil gear at the side if the tranny so your speed will read accurate ... they are available from many sources and color coded per gear ratio.
I disagree on the summit gears...Sorry have had awful set-ups and tons of time consumed from them. That is why they are price so low. Now I must say the gears I set up were 12 bolt...SO maybe the 8.5 might be better...lol. Highly doubtful though. Just remember with the factory posi unit there is no more support for spider gears and clutches are very low on support too. I have them but they are getting high priced. Might want to upgrade to a more user friendly eaton / yukon unit that can be rebuild way down the road hopefully... Oh and going cheap in won area and not as cheap in another will come back to bit you. So best to jusy save and do it right ONCE. Jim Would you put all new bottom end then stick used heads on the new bottom end??? So putting new gears on a used (i don't know posi ) is kind of the same thing???
If it helps any I had a gear man do this conversion for me. Dropped the car off with 2.56s, came back 2 days later, wrote a check for $1000 and left with 3.42 posi, and it's been perfect ever since. I'm happy:beers2: I didn't want to learn how to build rear ends on this car:idea2:
Dang thats alot, for me at least. I didnt expect it to be THAT much though.uzzled: I wanted to get that done, but looks like thats a little further down the road. Guess ill focus on the current project first :TU:
Question, and not to high jack this thread but the answer might help with the original question. What did that cost entail? a complete gear swap with seals, bearings, etc.? and did you have the ring and pinion already? I have a 8.5 with 2.76 posi, have the 3.42 ring and pinion new but uninstalled...you have any idea how much for them to just swap the ring and pinion with correct rebuild or seals etc.? 1K seems like a lot...but that might be with new gears etc. correct?
Thanks for all the feedback. The plan is to use all new parts for this conversion. Still looking for the parts. I have some leads. Anyone out there have the gears and posi available?
Got mine for 72 8.5 rear (same as 71) through Summit Gears: Richmond 3.42 is RMG-4902781 Deluxe Install kit: RMG-831021M (need to change side seals and bearings) Had GM 408 posi unit ; used it.
