Fummins

Newbie here trying to i.d. the rear end on my 1969 Cutlass S car. I read the rear ends on these cars are a tad different. The car was born with an a/t and a/c. The outer housing cover is a 12 bolt and it is a peg-leg. I definitely want to change the ratio with a posi unit in the 3.42 or 3.72 range. Rebuild costs, qualitymvendors on this site? Any tips to identify what im starting with? Thanks.

507OLDS

Unless the car was built in Canada,it came with a 12-bolt O-axle.They have a 12-bolt cover with a 10-bolt ring gear.Richmond makes two ratios for this rear,3:42 and 3:90.There are a few options for new posi carriers,available from myself,or Monzaz.He can fill you in.Basicly,if you want to rebuild the entire rear,with new gears,posi unit,and all the bearings/seals,etc.,you are looking at about $900.00 in parts.

Fummins

Thanks for the quick reply 507, appreciate it. The rear end/car only has 33k miles on it, is it necessary to do a total rebuild or are there options there? What other years/models will bolt up? Thanks again.

monzaz

Well NOW...That all depends on you and your car. IF you want to take a chance and you can determine good bearings from bad bearings give it a try...

IT is always a MUST to do seals as sitting or running they will GO BAD. Also with a rebuild kit you get all the parts you need to TOTALLY rebuild the rear from gasket, crush sleeve, bolts for the ring, pinion nut, pinion seal, all the shims to adjust pinion depth and Backlash, not to mention all the bearing in the rear center section... AXLE BEARINGS and seals are extra and not including in the rebuild kits as there are 2 different ones they can be depending on the year so we add them in later if needed.
Posi units are NEW -Recondition -
Eaton , trac lock, true trac etc.

Prices will usually be a bit more for this rear - it was only used 4 years and posi units are custom build parts. It is a good rear and will do the job and es specially looking to keep your original car ORIGINAL.

Jim
JD

507OLDS

If you are not concerned with originality,the 71-72 8.5" 10-bolt is the best for the money.They are the least expensive to build,compared to teh 12-bolt O-axle,or 12-bolt Chevy,but they do not sacrifice any strength.They are a nice rear.You could get a complete 8.5" 10-bolt posi rear,with all new parts,ready to bolt in,for $1,000.00.
One thing you would need to do,when converting from the 12-bolt O-axle,to the 8.5" 10-bolt,is shorten your driveshaft,so that is another expense that you need to consider.When all said & done,will it be cheaper to buy all the parts to build your existing 12-bolt O-axle,or swap to a rebuilt 8.5" 10-bolt?It depends on what your local shops charge to do gear installations,and what the shops charge to shorten a driveshaft.

Run to Rund

It would help to decide on what you want to do, because which rear and what you do to it can get expensive. For example, the 12 bolt has lots of aftermarket stuff available, including pro gears. The 10 bolt 1971-2 is strong but I don't know of any pro gears for it. The Type O that you have is pretty strong but more or less an "orphan" with less stuff available cheaply. You can buy aftermarket axles, a couple ratios of gearsets (as noted above), and a custom posi modified from an 8.8" Ford iirc. Do you plan on much strip use with slicks? Stick or automatic? Do you want it to look restoration correct? 507Olds and Monzaz have experience with the GM rears. Another option is a drop-in 9" Ford rear but it won't look original and would be justified more if you are going drag racing.

Fummins

Thanks Guys, sorry the late reply been busy on carb and timing issues. The car will never see the track and im not hung up on keeping it original. Figured this would be easier, lol.

Fummins

Maybe i just regear and leave it limited slip, probably cost me a ton of $$ in right rear tires though lol.