The rear in my car is an 8.5 for sure. It is stamped "ON" on top and code on it is 9795082. This is a 3:64 rear ratio from a 69' or 70'?? When I bought car this was in it already and was told its 3:23??
That's why I am asking. I am no expert on the rears. I looked at some old post and saw that "ON" code should be 3:42 or 3:64 depnding if it came from a car with or without AC. I know this is not the original rear that came with my car. my car was an original 350 2bbl peg leg. When I bought it the guy before me put in this rear,, rebuilt th400 ,and the 400 BBB which is out now. He said the rear is 3:23 but seems higher to me. What I do know that it is a 8.5. has the extra "meat" tabs on the bottom with the notches in it. Also is stamped "ON" . Can anyone confirm for me what the "ON" code should have? Thanks, Mike
ON shows up in my Cdn. GM Master Parts Book from '81, but doesn't agree with the years for an 8.5" rear. Possibly from another GM brand? 66 & 67: 3.55 PT, 68,69 & 70: 3.64 PT. Check George's site: www.buickperformance.com Pretty sure he has a script about finding axle ratios with the rear wheels off the ground. Based on driveshaft revolutions vs. wheel revolutions.
I realize by year model it should be a factory 8.5 but let's re-verify whether it is an 8.2 or 8.5. How is the driveshaft secured to the rear meaning U clamps, etc?
Rear 8.2 versus 8.5 ID from Roger "OPH" an expert if there ever was one: "Instead of looking at rear covers, look at the pinion yoke where the u-joint attachs. Does it have U-bolts & nuts ??? U-bolts & straps were on all different forms of 8.2 10 bolts. All 8.5's used straps & 7/16" headed bolts."
your best bet is to just pull the cover. chances are that rear could have been stock and rebuilt with a posi unit and a better ratio. I wouldn't go with codes at this point since its been 30 plus years and anything could have happened with the rear since then. either way its probably time for a fluid change anyway.
PLEASE POST some pictures for us to verify the rear . rear shot of the cover area with outer casting area if possible, shot of the yoke area and how do your springs mount ? on the top of the axle tube in the middle or off the front of the axle tube a bit on perch mounts? Bolt in axles or c-clip axles? You can check www.jdrace.com also for ID rear look under the bop rear section and look at some of the pictures. Ok? Jim
OK Jim, hear are some pics. They didn't come out that great but you can make out the "ON" code. I just need to jack up mark an rotate tire an count to see what it is. This is not the original rear to car since this was a 60,000 mile 350 2bbl "grandma green special" That began some transformation before I got it. Mike
Mike, That is an 8.2 rear axle, and the "ON" you are looking at is not the axle ratio code, but is the date code of when the center housing was cast. It looks like "D 11" to me, which would mean it was cast on April 11th. Duane
Mike, Here is an "ON" axle ratio code stamping. You will have to scrape and clean the axle tubes to find the codes on your rear end since they are hard to see with grease and dirt covering them up.
oh...thought the "tabs" at the bottom meant it was 8.5 then just looked at some other rear info and saw the tabs/notches are different on mine. look like i will search for a new rear???? 12 bolt maybe? need to dial in care a little better first. thanks, mike
james, thanks for that pic. helps alot. i guess it could be stamped anywhere on the rear? or is there the usual spot? Mike
