Early GM Differential ID - Help

Just got my hands on a mid 60's FED and I'm trying to ID the two differentials that came with it. 17 spline alxes and one diff has the spider gears welded up. Can some one tell me what these are and if so - can you still buy a full locker for them? Cast numbers in the photo's. Thanks

 

Looks a lot like a '55 / '64 Chevrolet................ here's a writeup on putting a
posi in one done by Tom Parsons.



http://www.chevytalk.org/fusionbb/showtopic.php?tid/223802/

 

Thanks

 

Spool that bitch !!!!!!!!!!!!!!!!!!!!!!!!!

 

I am being told this is an Olds rear end. Is there a source for casting numbers to verify what this diff is?

 

That configuration was used in Chevies from 1955 through the end of the 1964 model year. In 1965 Chevy went to a an integral style dif.

The 3707306 casting number you have was only used in for the 1956 model year and the cast date just above the casting number supports that. G266 trans lates to July 26th 1956.

In 1957 the casting number changed up to 3725899 for open and 3743833 for posi. 1957 was the first year for posi in a Chevy and it wasn't available until later in the model year.

Is there anything stamped in faintly on the passenger side in the area where the casting numbers were on the left?

 

The '55, and I think '56, too, had smaller pinion bearings than the later rears, not as tough.

 

Ask whoever it is that's telling you it's an Olds rear, if they can tell the difference between a circle and an oval.

 

From what I can tell, it says: PA731
It's real hard to read.

 

It is likely BA731. It is quite common for these alpha numeric dif stamps to be hard to read. This stamped number fits well with the casting date.

The dif housing was cast July 26<SUP>th</SUP> 1956. Then machined and final assembled on July 31<SUP>st</SUP> at the Buffalo NY plant as opposed to Detroit Gear & Axle. It started life with a 3.70 open ratio.

Ain’t no Olds.

 

Like everyone who knows has already said, it's a 55-64 Chevrolet pumpkin/pig/third member. You want a spool for it, the only place is BruneauPerformance.ca, a Canadian site. He also has other parts to beef them up. Post a pic of the FED. It was probably, at one time, a Junior Fueler, with that rear end; they used to build them light, and an Olds/Pont third member weighs 90 pounds, the Chevy is about half that. Butch/56sedandelivery.