Well I picked up a posi out of a 67 Riv GS, and I've been looking to make sure it is indeed a posi because I ordered it from Washington and had it shipped. I have been looking for the tag that gives me the code to tell me ratio etc. I have found a tag that says "use limited slip differential fluid only" so that gives me a clue, but I also found a strange number; 1372231 then under that a 1 and further down there is a O followed by a circle with a / in it followed by a 13. Anyone have a clue what that means? Thanks. Zach
You can open it up and look, its stamped on the ring gear. Should change the fluid and inspect inside anyways.
there's one simple test. If you spin one tire and the other tire spins in the same direction you have a posi.
that dont always work. some times the other wheel will spin right along with the one you are turning ...especially if the brake shoes are beyond wore out. remove the cover and check it. then you will know. had a friend once the bought a "posi" at a swap meet ...pulled the cover(with posi tag) off at home and the seller had swapped the posi guts out for a regular pumpkin with a couple of tack welds on the a spider gear to make it seem solid if you spun the axle at the swap meet.
OK, I have my 67 Buick chassis manual open to page 40-79, and there is a schedule that shows the codes for the rearend. Under the 49000 series (Riviera) listing, the only open rearend came with a 3.07 ratio, and had the code letters PJ, followed by the date code, stamped into the axle tube near the center section. If it is an open rear, It will look like this, O PJ 203. the O is actually a circle, and the 203 is the day in the year (in this example July 22). If the rearend is a posi, the circle will have a X inside of it, and have one of the following codes stamped after it. For a 3.07 posi, the code is PM, for a 3.42 posi, the code is PY, and for a 3.91 posi, the code is PS, and as before, the axle tube will be stamped with the day in the year following the letter code. The 3.42 posi was standard on the Riviera GS, but it could have been ordered with another gear ratio. If yours has the PS code you just hit the mother load. You may have to use a wire brush to get through the rust and dirt and find the code. Mine have all been located on the bottom of the axle tube on the drivers side of the center section. Don't forget to change your speedometer gear when you swap the rearend. Later, Randy
I gotta check those codes today, I swear I can never find them when I look. I turned it over and I do thinks its a 3.42 but as it had been pointed out, that doesn't mean it really is a posi. Got to find those codes! Zach
Zach, You must be a glutton for punishment, scraping rust and rolling the heavy a$$ rear end around and spinning axles and writing posts on here...just get a 9/16 wrench (or whatever, I forget), a screwdriver and a little hammer, a pan to catch a little bit of lube, and take the rear cover off. Count the teeth on the ring and the pinion gears, get a calculator, and divide the big number by the little number. That's your gear ratio. Or read the numbers on the end of the pinion or stamped into the ring gear outer circumference. Fifteen minutes max, and then you don't have to guess about anything.
Fine, i'll just take the damn cover off! jeez. I'll let everyone know what I got when I do. Thanks for all the help.p Zach
OK now that its all opened up and I know its the real deal, what the heck is the next step? It looks real good inside, is there anything I need to yank out and rebuild or replace? I know the lube will need replacing and the gasket for the cover, which I am planning on chroming. Is there anything I missing, could it really be as simple as lube and a gasket? Something tells me it isn't. Thanks Zach
Zach, do you know anyone who's familiar with rear axle assemblies? At the least I would have them check backlash and the contact pattern between gears. If both are good it should be safe to assume that the carrier and pinion bearings are OK. Devon
Ill ask around, bet my old man would know, but I think I hold off until it gets warmer here in Chicago, its sooo cold, its about 2 right now. Zach
Zach, few mechanics can build a rear as well as the factory guys. I've never heard of an original rear end whining or anything. Sure, they blow up sometimes, but only after a lot of abuse. I just bought a 3.42 posi as a spare and I'm going to clean it, paint it and replace the fluid. Then store it. I suggest you just do the same.
