Hi All,

Trying to identify the rear end I pulled from a cutlass with the 442 package.

Thanks

Tim

 

1970 O-Type rearend per the casting number.

https://www.supercarsunlimited.com/i...id/diff_id.htm

The picture is too blurry to make out the axle stamp for the gear ratio.

 

I'll have to do a little more cleaning / searching I did not see any axle stamp

 

you're only 5 bolts away from looking inside

 

Oh. I thought the pic of the vent tube area had a stamped code hidden somewhere in the blurriness.

 

here are the places the axle ID suffix codes are located.

Jim

 

Hi Jim - I have a question. You assisted in providing some information regarding my axle/differential in the past.

I note the OP posted an image of a 12-bolt, and the diagram you provided is a 10-bolt. In your diagram you reference the code on an Oldsmobile is on the backside of the passenger (axle) tube upside down. However, my 1971 Oldsmobile CS w/ the original 256 ratio rear-end has the stamp located on the passenger side (axle) tube on the front side - not the back side. Did you flip the Chevy for the Oldsmobile location in your diagram or am I missing something. I think Kenneth's is located on the front side of his axle tube, as well.

Thanks, Norm

See my axle tube/differential here >>> https://classicoldsmobile.com/forums...mation-131951/

 

Hi Jim - I did note on the post you assisted me w/ (identified above) I believe it was somewhat ambiguous as to exactly when the stamped code was appearing on these axles. I guess Oldsmobile elected to switch the location of the stamped code somewhere around when - 1968, 1969, 1970 you figure?

Taken from your previous helpful information:

 

Yep, the code for the corporate 10 bolt is on the front side and the code for the O-Type is on the backside and upside down (all three of my O-Types have the code in the same location and orientation).

Here's a pic of my 1970 O-Type rear:





1968 Heavy Duty O-Type is in the same location:




And of course as already noted the 1971 corporate 10 bolt is on the front side:

 

Ah. Thanks Kenneth. This is making more sense each passing year (for me)! I have a tough time learning the axle/differential types and code locations. Thanks, again.

 

WHEN YOU SAY CORPORATE REAR you are talking about all of GM.... So there is NO specific as GM wanted... 1973 all gm cars mid size were 8.5 so it was put where the Chevy stamping was located
when the divisions were still split individual the rear end diagram is correct for divisional rears. 10 and 12 bolt.

7.5 was a corporate rear also
14 bolt 10.5 corporate rear GMC and Chevy
pretty much in the 70's GM switch to the corporate system...they to were phasing the motors also as if you remember Oldsmobile customers freaked when they got a 305 Chevy motor in their Olds instead of the 307 Olds motor...lol.

Jim
JD

 

Finally found the elusive R2
So it's 2.56 open?

I thought those had 10 bolt covers.

What besides two bolts on the cover is different than the 10 bolt R2's








Does the 358 on the carrier indicate anything useful?

Thanks for all the help.

Tim

 

That is a standard 2.56 open carrier. Not worth much to anyone.
Olds only used the O axle in 1970 UNLESS the car was built in Canada, then it got a Chevy 12 bolt.

 

2.56:1 ratio was available on multiple types of rearends.

Just about everything. In 1970 the O-Type axle bearings were the same as the 71 and later 10 bolt rears, but other than that no parts interchange.

It is the casting number for the O-Type 2 series open carrier, so it is very useful to ID the carrier.

 

The replacement frame came from a Chevelle is this rear any better than the O-type I listed here?

 

This web site says that is a 1970 version 2.56 Chevy rearend.
https://www.chevellestuff.net/1970/rear_axle.htm

Need to know what you mean by "any better than the O-type". "Better than" is very subjective and can depend upon a lot of factors such as strength, parts availability, cost of parts, gear ratio options, etc. They are both crappy 2.56:1 gear ratio rearends and for some folks a 7.5" 10 bolt with 2.73 gears would be better than both of those. It all depends upon your definition.

 

'o' type is strong and has bolt in axles... will be more expensive to build
10 bolt Chevy will be less expensive and more ratios to choose from but will be weaker.
So you need to figure out what you need more.
Jim

 

Pretty sure that was 68 and 69 only. I will have to check where my 1970 was built, has a 2.78 Type O 12 bolt rear.

 

My buddy dropped off a rear-end yesterday, he

Thought it was QV at first but QN makes more sense best I can tell










thought i might be able to use it...
Best I can tell it's a BOP Limited slip QN 3.08 with the 8.2 carrier.

Certainly better than my type O 2.56 open I would think.
Is it a direct swap for my 70 cutlass vert?

Am I better off rebuild a type o I have two with 2.56 open in them?

 

Holy twisted LCAs Batman!

If you want your '70 to remain "original appearing" I think your only choice is to rebuild your Type-O. I upgraded mine to 3.90 gears w/ a Supercar's posi carrier. If originality is not important, it's a whole lot easier (and likely cheaper) finding parts (mainly gears) for this 10-bolt than for the Type-O.

 

Couldn't resist found a BOP out of a 70 GTO being replaced with a ford 9 inch.
With disc brakes all ready to go. The ad said 3.73 out of a 70 GTO but it looks like a 72 3.55 was swapped at one point.

 

3.55 XH code rear. Pretty decent. Is it rebuilt or used?
If it is used...Try a burn out right away...Those posi units after 50 years are usually not working.

 

Used, I believe he just changed the oil. Unfortunately, it won't be in a working vehicle any time soon.

 

Ok, Well crossing my fingers for you. Jim

 

021 XH

what does 021 represent?
72?
2nd month 1st week of 70?