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1967 4-4-2 Rear End Ratio Question for the Experts
Hi guys,
I have a 1967 4-4-2 Holiday Coupe (no A/C) with TH400 and O-type rear end with Anti-Spin. Determination of the rear end ratio via the car on jack stands and rotating the rear wheel method, and via tire height/rpm's/speed calculator both point directly to a 3.42 to 1 ratio. Can someone verify that the 3.42 to 1 Heavy Duty Performance Rear End was an available option for this car?
Thanks
Chris
Last edited by Dream67Olds442; Aug 24, 2023 at 09:33 AM.
My 67 442 has a 66 Pontiac 10 bolt, posi with 3:91's which i believe to be correct for this car. I was able to see the ratio stamped on the ring gear as shown below. Doubt this helps but maybe your ring gear is stamped with your ratio if original GM?
From what I read the 355 non posi was the standard gear/rear for a stick 67 442 but various ratio's could be ordered. and the 10 bolt cover P type was used along with the 12 bolt cover Olds rear.
Thanks to all who have responded so far, much appreciated! Unfortunately, unless I'm confused (which is often the case), I don't think I see an answer yet.
Again, here's what I'm fairly confident of:
- The car is a TH400 automatic
- Certain I have an Old's O-type rear end with 12 bolt cover and 10 bolt ring gear.
- Almost positive it has 3.42 rear end ratio as determined by multiple methods (see original post)
- Certain it is a posi unit
What I want to know? Was a 3.42 ratio posi an available option in '67, and if so, does anyone know the RPO code?
Thanks guys!
From what I know, all ratios were available in the O-Type over all the years it was used, so yes your car could very well have 3.42 rear gears. I don't have any RPO code information, though.
I archived this information that Brian Trick posted many years ago. It shows most of the various ratios that were available. The "& anything numerically higher" means 3.91, 4.33, 4.66, and 5.00 ratios.
O-Type 12 Bolt
Here is a list of the posi units & what gears they will fit:
never trust anything.. jack up the car, put jack stand under axel., mark the wheel, mark the driveshaft put in neutral and turn driveshaft ten times and count how many times wheel turned divide by ten thats your ratio
never trust anything.. jack up the car, put jack stand under axel., mark the wheel, mark the driveshaft put in neutral and turn driveshaft ten times and count how many times wheel turned divide by ten thats your ratio
FStanley - Thanks for your response, but I already did that, please reference my original post.
I ended up with one of those HD O-Types (3.42 TL code) before I knew there was a difference in axle shafts between the standard and heavy duty rearends. I needed a shaft for my 3.23 rear and found an O-Type for sale just over the border in SoCal. Bought it cheap, paid through the nose for shipping, then discovered it had the HD 31 spline axle shafts. Doh!
I ended up with one of those HD O-Types (3.42 TL code) before I knew there was a difference in axle shafts between the standard and heavy duty rearends. I needed a shaft for my 3.23 rear and found an O-Type for sale just over the border in SoCal. Bought it cheap, paid through the nose for shipping, then discovered it had the HD 31 spline axle shafts. Doh!
My 67 442 has a 66 Pontiac 10 bolt, posi with 3:91's which i believe to be correct for this car. I was able to see the ratio stamped on the ring gear as shown below. Doubt this helps but maybe your ring gear is stamped with your ratio if original GM?
Well the rear end in these pictures are as follows
K 17 6
CAsting is Pontiac
K = 11 month November
17 = 17th day of November
6 = 1966 Year
So really this rear would be in a EARLY 1967 car.
The ratio is 3.90 since it is Pontiac...Pontiac used 10 pinion teeth and 39 ring teeth 3.9000
Olds did the 3.91 ratio which was 11 teeth on the pinion and 43 teeth on the ring. 3.90909090
Now I am pretty sure that early 67 cars did still get Pontiac rears 8,2 ruing gear in the performance cars. and later cars got the 12 bolt olds 12 bolt cover rear 8.5 ring
BUT since I have learned a few years ago OLDS 12 bolt had some castings with FLAT spring perches that would be 1966 model year rears...... I just do not know anymore...lol
I was just so amazed to see the 12 bolt olds with flat perches... Because 1967 ALL rears had raise spring perch pockets. 1966 were flat with bolt on cups and bolts to hold the base of the spring top the flat perch..?? So there you go...
Great info sir, thank you! My 67 442 had W30 options added later in life, so i think this rear end was likely added along those lines. I did have a buddy say my rear spring perches did not look the same as his 67 Cutlass? I think these pics show the perches fairly clearly. Thoughts? Not trying to steal this thread but looks like Original poster got his questions answered, with zero help from me as usual, lol.
Well the rear end in these pictures are as follows
K 17 6
CAsting is Pontiac
K = 11 month November
17 = 17th day of November
6 = 1966 Year
So really this rear would be in a EARLY 1967 car.
The ratio is 3.90 since it is Pontiac...Pontiac used 10 pinion teeth and 39 ring teeth 3.9000
Olds did the 3.91 ratio which was 11 teeth on the pinion and 43 teeth on the ring. 3.90909090
Now I am pretty sure that early 67 cars did still get Pontiac rears 8,2 ruing gear in the performance cars. and later cars got the 12 bolt olds 12 bolt cover rear 8.5 ring
BUT since I have learned a few years ago OLDS 12 bolt had some castings with FLAT spring perches that would be 1966 model year rears...... I just do not know anymore...lol
I was just so amazed to see the 12 bolt olds with flat perches... Because 1967 ALL rears had raise spring perch pockets. 1966 were flat with bolt on cups and bolts to hold the base of the spring top the flat perch..?? So there you go...
