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1956 "AB" is a 3.55 open (non-posi, and posi was not generally available in 1956), with a powerglide, in a passenger car. The unit came from Detroit Gear and Axle plant.
Also no idea about the D at the end. Can you post a picture.
Last edited by emccomas; May 25, 2019 at 05:51 AM.
1956 "AB" is a 3.55 open (non-posi, and posi was not generally available in 1956), with a powerglide, in a passenger car. The unit came from Detroit Gear and Axle plant.
Also no idea about the D at the end. Can you post a picture.
"AB" is the code for a 3:55 rear with an automatic in 55-56 full size Chevrolets, but in 1957 "AB" was the code for an open 3:36 in a full size with an automatic. With a late July casting date, and an August 2 assembly date, it might have been a 56 rear, but I think the odds are better that it's a 57?
After checking a little, I think the "D" may indicate a rear assembled in Detroit, as opposed to Buffalo.
Below is a specification chart for 55-57 Chevy's. The rear axle codes are on the third page.
Chevrolet was still building 1956 cars in August of 1956. I own a 56 Bel Air 4 door sedan that was build in the middle of August, 1956 with many of the components dated early to middle August. I don;t recall now what the date on the rear end is.
thanks for all th eanswers !
i was out this we so unable to take a picture , here is it .
so i have a rear end from 1956 with a 3.36 or 3.55 rear for an automatic .
Read the following closely----------------------------IN 1956 THERE WAS NO SUCH THING AS A 3.36 RATIO FOR CHEVYS.
The choices were 3.55, 3.70, 4.11 for pass cars. Corvettes could have 3.55, 3.70, 4.11, 3.27.
Positrack was NOT an available option for 56-----------------------------BUT a VERY, VERY small handful of 56 Corvettes (such as the Sebring prepared cars) got an extremely early, more or less, prototype postrack rearend, called Hi Torque, and those were stamped HT. Over the years I've tried to find documentation, drawings, photos, information or a surviving example of a 56 HT posi rear. No success so far. And I don't even know if they were built in a 306 case.
I think the confusion over this issue is that one poster suggested the possibility that this rear end might be a early 1957 passenger car differential, as opposed to a late 1956 passenger car differential.
The casting date of G 24 6 (July 24, 1956) , and an assembly date of 8 02 (August 2nd) "sort of allows for that possibility, but I do not think so.
I am convinced that this differential is a late 1956 unit. The AB code for 1956 is 3.55 open rear end. The AB code for 1957 is 3.36 open rear end.
I own a 1956 Bel Air that was manufactured in the middle of August, 1956. Most of my components are dated August of 1956.
It was originally mentioned that the third member case was a 306 casting. THAT ALONE BY ITSELF LOCKS IT IN AS A 56. PERIOD.
The rearends for the 57 model year started off with a totally different third member case, 3725899 (the 3743833 posi case came along in LATE Dec 56). There is NOTHING, and there NEVER HAS BEEN anything that suggests a very early 57 got a "left over" 306 third member case.
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corvette rear end casting
