hello all. are 1965 Type "O" & 1967 Type "P" Differential ring & pinion gears interchangeable? i have a 1965 F85 w/ a type "O" open diff & 3.42 gearing. i also have a posi differential "P" type rear from a 1967 442 that has 3.08 gearing. ideally i'd like to upgrade the gearing to the "P" type posi unit from 3.08 to the 3.42 from the type "O" will this work? do the ring & pinion gears interchange?

 

all 1964-1967 rears are 10 bolt 8.2 rears and all use the same ring and pinion gear sets.
All carrier breaks are the same.
2.56-2.78
2.93-3.23
3.36-4.33- and beyond.
THE pinion seals and yokes are different from the B/O to the P axle.

The B axle bearings on the GS are also a different size as are the axle shafts

Wagons A-body are also different axle bearings and axles all depends on the year early 64 65 or later 66 67.

Hope you got your answer from this info. Jim

JD

the 3.42 gears you have are they from a housing that has 12 bolt cover or 10 bolt tempest looking cover ? Please provide the tooth count of each gear if you can and the ring gear bolt size. Thanks, Jim

 

 

Sure did Jim thank you!

 

Jim, I know you know this, but Olds did additionally use their new O-type in '67.

 

But not in 65.

 

10 bolt Jim. Not sure of ring gear bolt size since I haven't pulled the differential yet

 

yES BUT THAT WAS LATE 67, EARLY 67 THEY STILL USED THE PONTIAC ONE FOR THEIR PERFORMANCE REAR. Sorry for the caps...

I refer to it as 12 bolt olds A body 10 bolt ring 12 bolt cover. I asked the 12 bolt 10 bolt thing cause he said 3.42 gear set. Which did not seem to be a ratio in the 10 bolt 8.2 rears... 2.93 3.08 3.23 3.36 3.55 3.90 etc.

Jim
J D

 

It sounds like you have two BOP 8.2" rears,so yes,the parts with interchange between the two housings. If either one came from a GS,then it would be unique to itself.
They should both have 27-spline pinion,and 28-spline bolt-in axles. No c-clips. The Chevy 8.2" will have a 25-spline pinion and c-clip axles.

 

The O-type was supposed to be available of at the start of the '67 model year, but I have not seen early examples myself. I know they were in production by mid-year. Even late year they still used the P-type almost exclusively for performance rears, including the W30s.

 

I rebuilt a rear for a local guy,with a 67 442. It came with the 12-bolt O-axle,3:23 posi,and I switched it to 3:90's. Not sure when the car was built though.I've done other 67's with the 12-bolt O-axle,but again,not sure when they were built.

 

Have you seen any '67 (A-body) O-types with any steeper gears? Seems all 3.55+ were P-types with 4-pinion carriers. 3.55s were "standard" with 3-spd manual and 4-spd wide ratio, and 3.90 std for the close ratio 4-spds.
Anti-Spin was additionally an option. Seems implausible that one would not also get the G80, but the open 3.55s and 3.90s are out there.

 

Good question Kurt.I would have to say no,at least with me.I think all the 67's I have dealt with,had 3:08's or 3:23's. The 31-spline option for the O-axle started in late 67,but did it ever make it into a 67 car,or did it go into all of the 68's?

 

According to the Service Guild Bulletin, Type O was available May 66, iirc. I agree that they apparently didn't have any stiff ratios until late 1967.

 

If the Type O was available in May of '66 then why were they not used in any 1966 Olds A body cars since the 66 model run would not have ended until early July. Did you mean May 1967?

 

OK Jim and Brian -- Here's my experience ( first-hand, not hearsay). My 67 W30 ( bought new( feb build date)) came with type P , cone posi, 3.90 gears.


My other 67 442 ( build date 05B May) - came with the Type O in question -
3.42 posi with 31 spline axles --
This is the rear exactly like the one Brian built for my current W-30 tribute car. I restored it and it is sitting here ready to go back into the tribute car if and when i decide to quit racing it and return it to a street driven car.


So the "physical evidence" to your question is sitting right here in my shop.
Its just too bad that we cant get a 4.33 or 4.56 gear set for one of these units. I also have a Type O with a 3.08 open that could be used to fit with the lower gears if a gear set with the "fat" ring gear were available.


Brian built mine with a 4.10 Richmond "fat" gear set that he machined down to fit my Type O carrier!

 

What i still find hard to understand is why they went back to producing and installing 28 spline Type O's in 68's after having started using the 31 spline axles in late 67. Its my understanding ( i think i either heard or read it somewhere) that the late 67's and some of the very early 68's were the only ones to get the 31 spline axles --- then for some odd reason, they reverted back to using the 28's for the rest of the 68's and later? Can any of you guys confirm this about the reverting back to the 28's in 68