57-64 Olds/Pont. The earlier 56 a nd back had 10 spline axles for starters, were smaller, and used a bolt on yoke, so the pinion had a "flange" and not "trunnions", like what you have. You do have the slightly "lighter weight" third member case; the other "stronger one" has three ribs. Nothing to worry about just the same, yours is plenty strong. 57-58 had 29 spline axles, 59-64 31 spline axles. Posi available in 58 for 29 spline axles is extremely rare. Lots of 31 spline Posi's. There are aftermarket parts galore, see FabCraftMetalWorks.Com. There are also 35 spline setups available. I am Butch/56sedandelivery.
You "BELIEVE"...it has 31 splines..? Did you...count them ? There were two castings. Some with two large ribs (as shown above) and some with three. BOTH were for the 57 to 59 housing. The early (55-56) center casting was very small compared to the later 57/59 casting. Maybe 3/4 the size. There is a couple of different posi units available. They each have their own spline count. Mike
I had counted them before and I thought it was 31 spline but I’m working out of town and can’t go recheck. The car was recently inherited in pieces and I ‘m trying to find parts and figure out how to get it back together in my down time. Appreciate all the help.
I have a 57 open with 31 spline side gears. Axles are of later year and splines are shorter (length cut to fit) as compared to photo #4.
Enough clues here to make me think it's a '23 Model T, most likely built in the late '60s Can you post pictures of the rest of the car?
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