['ol Pinion head]

All factory 64 & 65 Pontiac 8.2 Safe-T-Track & Olds 8.2 Anti-spin units were 2 pinion units.
All '64-65-66 model production 8.2 Pontiac housings were gray iron... very susceptible to pinion deflection under high torque loads. Pinion deflection is big reason why all gray iron GM 8.2 rearends blow up when exposed to heavy torque loads, no matter what posi carrier (rebuilt 4 pinion, eaton, auburn) & good aftermarket axles are installed in it. The weakest gray iron housings ever cast were used in '64-66 Olds & Buick 8.2 rears, they are junk.

4 pinion cone type 8.2 Pontiac Safe-T-Track carriers were introduced for '66 models with the low ratio 3.36-4.33 gearsets. They were also used by Oldsmobile in '66. Pontiac dealers were advised to replace destroyed '64 & 65 two pinion Safe-T-Track units with the 8.2 HD 4 pinion Safe-T-Track carriers.

If one has a Pontiac 8.2 2.56 or 2.78 Safe-T-Track rearend, it is a 2 pinion, as no 4 pinion units were made for the high ratio (2.56 & 2.78 rears).

Mid ratio 4 pinion Safe-T-Track units were produced in early (through '69) & '70-72 8.2 Pontiac styles. The mid ratio 8.2 Pontiac carrier was used with 2.93, 3.08, & 3.23 8.2 Pontiac gearsets. While there were many 4 pinion Safe-T-TRACK rears built with gray iron housings, there never was a 8.2 HD SAFE-T-TRACK rear built with the mid ratio gears & 4 pinion carrier.

To qualify as HD SAFE-T-TRACK, the 8.2 Pontiac rear was built with the nodular housing and the 4 pinion carrier AND the special forged axles. Tons of '67-72 Pontiac 3.55 SAFE-T-TRACK rears were built with nodular housings, but with the the standard duty '67-69 or '70-72 Pontiac 8.2 axles.

Buick built their own HD 8.2 BUICK 10 bolt rear from '68-70. It takes it's own gearsets (like their 2.93's, 3.08's, 3.42's & 3.64's) & its own different series 4 pinion posi carriers. These Buick 4 pinion 8.2 posi carriers had different spline side gears & their own stagger for different ratios. If one is not careful buying used parts they can end up with a 4 pinion Buick posi carrier for intended Pontiac 8.2 usage.. The '68-70 Buick 8.2 posi unit & single track carrier takes a 12 bolt carrier bearing on the drivers side & normal 10 bolt carrier bearing on the passenger side