'66 swap safe-t-track diff into a standard diff axle
 

I own a 1966 Pontiac GP with an original standard differential rear axle. I also have an original 1966 Pontiac GP safe-t-track differential rear axle. I would like to swap the safe-t-track differential into the GP rear axle and ideally do so without removing the rear axle from the GP. Both differentials are in good working order.

The 1966 Pontiac Chassis Shop Manual states "The Safe-T-Track differential is similar to and interchangeable with the standard differential case assembly (the ring gear and side bearings are identical)".

From a practical standpoint are there any issues of which I should be aware before attempting to swap the differentials? I could of course simply swap the rear axles but would prefer not to do so unless there are good reasons.

Axle ratio not an issue for this swap.

The one & only time that I did this (Dana 44) I got super lucky & the gear pattern was within spec. I was working with a pro, just in case.
Check your gear pattern, of course & be prepared to swap the whole diff or jockey the R&P.
Good luck!

The parts are a direct interchange from one housing to the other.......sort of. You will need to go through the standard same process you would perform if you were changing the ring and pinion for example. Unless you win the lottery on a regular basis, there is no way the pinion shims for pinion depth and the case shims for backlash and case preload will be the same for both housings. That;s why there are hundreds of combinations needed to get those items right. The variations in the housings, cases and ring and pinion gears will all be compensated for when you "set up" the parts in their new homes. If you have done this type work, it's pretty straightforward. Lots of video on Youtube and the process is the same for any GM rear end other than the old drop out 9.3" rear. Inch Lb. torque wrench, dial indicator, some brass drifts. Very long breaker bar or pipe to tighten the pinion nut. Other than that, a service manual and basic hand tools and you can do it.

Based on mgarblik's comments I think I will swap the rear ends instead of swapping the gears. In my particular case there would seem to be fewer issues to sweat over.

I've done that swap a couple times no issue. Use the shims that came with the gear set in the same order. I mark down the number but today you could take picts before removal.. Frankly, I'd pull the whole rear end and have the new one going in all cleaned up with new rubber or spherical bushings...

Swapping rears is not that hard, its even easier if ya weld up a support bracket that attaches to your jack to hold\move it. Disconnect driveshaft, pull axle shafts so you can disconnect and hang the brake backing plate assemblies on the frame with some stout wire which makes it so you can reuse existing brakes, plus there is no need to open any brake lines, and the axle assembly is much lighter. Unbolt control arms at the axle only.

Idk if the 66 housings are N case housings but I’d think if they were you’d definitely want to keep the N case. . Look on top of the housing where the pinion is for the big cast N

If your not going to race this car, it will handle and drive better with the standard rear end. The standard rear end is always in prefect revolutions. The outer wheel spins more then the inner wheel during a turn. The Safety-Track has clutches that have to be over come buy the engines power. Next time you get a chance and have both go into a lot and make some figure eights with each kind. You will notice right away how much smoother the standard rear end turns. By the way both back wheels propel the car with a standard differential, it's just when one wheel spins the power will flow to the spinning wheel.
When driving in the snow I hated posi rear ends. You would go up a hill and both back wheels would spin and the whole car would go sideways, were as the standard rear end would have on wheel spin and the other keeping the car straight..

Back in the glory days of the early sixty's all those Pontiacs used standard rear ends.. Smokey said one of those clutch rear ends wouldn't last 100 miles..

If the Safe-T-Track unit is same series as the open one (1,2,3) then swapping the ring gear over and same shims it had should line up very good usually but regardless the backless should be measured before and after to compare and the preload remaining. But again also just swapping whole sub B ain't bad either. You could clean paint whole other one nice in advance.