Non... chevy 12 bolt info?

[TC]

Any experts here on type "o" 12 bolts?

This might be a stupid question, but did the olds type "o" A body rears ends come in pontiac and buicks too, just different id codes stamped in them... or is it an olds only housing?

The one I have doesn't have the id codes on the axle tube where they normaly do. It does however have the gear ratio code "TY" on the other side of the tube. The info I have found so far says it's an olds 4.33 posi, and would be correct for a '68-'69 cutluss... not sure if it came in the high HP (442's, W30... ect) cars only?

The only thing I can find for a date code, is 8-5... '68 5th month?

Next question, could it have been a special order or dealer only item, and thats why there's no id code? I've been told it's rare to find these today, and seems like an option not many people would have orderd on there car... any one actualy know of any cars that came factory with these?

Also, Any one seen one for sale lately and have a ball park price of what they go for?

Thanks in advance for any info you might have.





Tom

[Chevy454]

Where's Dave H (dehw31)...I bet he knows!

[PeteLeathersac]

FWIW, a few years back I sold a 12 Bolt Posi out of a '67 330/310 Cutlass.. I looked online for casting info etc as there was a big K or M or some letter cast into it but never found any more than the code/ratio either?. I never cracked it open as it sold quickly but I wanted to as I'd read Type O's had 10 bolt rings even though a 12 bolt cover?.
Also from what I understand, the 'O' rears had outboard axle retainers not c-clips like Chevys and were preferred by racers because of this...also some guys converted these axles and/or retainers into the Chevy rears?.

~ Pete

[SmallHurst]

Sorry, I don't have my Capt. Crunch decoder ring with me. I will try to do what I can.

Passenger side tube will have the 2 letter code stamped on it. As for stock gears, most of the time they stopped at 3.91, but a few rare ones had the 4.33's. You could go higher but, those were dealer installed.

Those were Olds only rears. They will hold up if you are using treaded tires, but if you use slicks with them, they will show their weaknesses.

If you have a '68 rear, if it is a 3.42 or steeper it will have 31 spline axles. Otherwise, they are 28 spline. An oddity for certain.

If you are looking for parts, I have the name of guy who rebuilds these all of the time. The new richmond gears that are available require the carrier that was for the taller gears (my brain has lost that 3 number code?) You can go to Reider gear and they have new posi units that are reworked Ford setups. Or you can have some fun, you can get a Richmond gear Lock-rite locker for an 8.5" GM axle and it will slide right in. It has a little noise, but it does the job!!!! Casey Marks built the one that I have under my car right now. The 3.9 richmond gears are a little noisey, but I don't really care under full throttle!

[TC]

Thats correct, Pete

It's a 10 bolt ring gear, I think I read some where, that it's still a stonger unit and is not the same as the olds 10 bolt rear.
I think I also heard the axles interchange with chevys...but I'm not certain if thats true.

The the clutch set up on the posi unit definantly doesn't look like any chevy I've ever seen...(see attachment)




Tom

[TC]

Thanks for the info, Rusty

I didn't pull an axle to to see if it was 31 or 28 spline, but there's no ring gear spacer on it, so that would make it a factory 4 series (part#588) carrier correct?...or am I thinking backwards on how that works?



Tom