Whats up guys I plan on putting a posi unit in my 72 skylark. I currentley have sotck peg legger with 2.73 gears and the stock converter but I rebuilt the tranny with a b&m transkit. So i been shopping around and I see all these 30 spline gm posi units so can I just throw that in my skylarks rear end or no? Ive been told that our cars are 28 spline so would I need to get new axles right im guessing? Thanks for the help:beers2:
You can get an Eaton or Yukon Posi in 28 or 30 spline. The axles will need to match the spline count. The good news is you have an 8.5 if it is the original 10 bolt rear that came in the car. Some 72 Skylarks came with a Canadian 12 bolt rear. There are lots of parts and gears for the 8.5 Buick 10 bolt, and it has bolt in axles. Good sturdy rear to build.
Thanks for the help I got a posi unit out of a 68 riviera but I dont know what spline axles it had I was out there all day and I counted 28 once and 30 once. I was at the junk yard like 5 hours and tired so I dont know for sure does anyone know by chance if they came with 28 or 30 spline thanks for the help Russ.
I am assuming you are in CA (Cali72). I have a Ford 9" made for a Chevelle by Moser for sale. It has 4.56 gears (also have 2.56:1), a detroit locker, and disc brakes. $1500. I know the ratio's availabe are not exciting for a Bick guy. I am in SoCal. send me a message if interested.
That would be cool but I dont have 1400$ Here are all the numbers I got of this differential 1375349 41-12 315 32085 085
The '68 Riviera carrier is from the '67-'70 9-3/8" rear end family, not compatible with anything else. That's a rare piece though, with the 3.42:1 ratio you'll have no trouble selling the carrier and gears in the "parts for sale" section here (you did grab the pinion gear too, right?). It'll fit Riv/Electra/Wildcat for the years mentioned above. Also, while it might seem to be an easy job to install a posi carrier, a lot of work and special tools are required to ensure proper bearing preload, pinion depth, backlash and gear contact pattern. Not exactly a good do-it-yourself project first time around. Devon
Damnit I was trying to put it in my 72 skylark I was hoping i could but I am located in northern ca. Yea I am currentley goin to school to be a mechainc I rebuilt my engine and trans so next was the rear end. Some of my buds said they thought we could take the pinion gear off and put mine on but the carrier is to big im guessing right? How could you tell the ratio from those numbers? O and I can take pics of it if anyone wants to see em
Sorry, the 9-3/8" carrier is a monster compared to your Skylark's. The ratio is indicated by the 41-12 stamped on the ring gear which shows tooth count on both gears. 41/12 = 3.417. Look through the "parts wanted" section first, to see if anyone is actively looking for a big car setup like that. If not, try a new thread in "parts for sale" section, but before you do take a moment to read the sticky notes at the top of that forum to help avoid confusion with the sale. Devon
Hmm dang you reply fast yea I got it out of a 68 riviera. So anyone have 8.5 they want to trade for? Lol yea when i was under the car taking it out I was thinking damn this rear end is huge! lol it had the stock heavy duty ac delco shocks on it still.
your good news is that you have the 8.5" rear end. Posi carriers are relatively cheap for that one, as are gears. Plenty of aftermarket support also. There is stuff on Ebay all the time, too, if you like that route. Posi carriers go for in the $125-$225 range used or reconditioned If you are a smart shopper. New aftermarket might go $350 or $400. Theres a lot out there, and you pretty much get what you pay for. Good luck!
I got a question for you rear end guru's. Did the 8.5 inch rear ends only come with oval covers because the one on my skylark isnt perfectley round my buddy said that his 68 firebird has the same cover. The cover is round on the top and bottom but goes straight in the middle he says it is an 8.2 I just want to confirmray:
Ive seen a lot of covers on the 8.5s. And you cant rule out someone switching one out at some time. completely round, "cutouts" on the sides, oiling grooves, no oiling grooves...lkots of possibilitites. (I believe the Buick 8.5s did originally come with the "cutouts" on each side of the cover.) BUT the best way to tell an 8.5" rear by observation is to look for the two square tabs sticking out from the diff housing on the lower side, below the diff cover, at about the 5:00 and 7:00 positions. or shoot a pic and post it here.
