Decoding rear axle housing numbers C1

[firstgear]

these are the cast in numbers on my rear differential housing
E2363
3726898
GM T 4 (the Tand the 4 are on the side of the GM, the T above the 4)

these numbers are stamped on my rear differential housing
BB0529

ok..I give up...I have been to Google and back....can't find a source...someone must know what it means.....

thanks!!! out of a C1

 

[Vettefreak100]

I have that information at home and will get it as soon as possible. It's in the corvette chassis restoration guide. If it doesn't have a giant P on it then it isn't posi....or someone added a positraction unit to it by grinding out a rib in the housing and installing one. Look to see if there is a tag on the rear housing bolts. There was different tags that determined what ratio it was too. I'll see what I can find when I get that book.

 

[Vettefreak100]

56-62 non-positraction units had part number 3725899 and part number 3789812 was used for a positraction rear end according to my book. I cannot find out what the numbers means because the BB is not the two letter code to determine what the car had in it (eg. in 1960 AH was a manual with an open differential and a 3.70 ratio and AP was a 4.11 positraction unit.) The rear end has probably been blown up sometime in it's life and someone replaced the center chunk with one found out of a junkyard that was used on another GM model. I think my 1961 had a BB code on it bc the differential was not a numbers matching part and it was a 3.36. I'm sure that it is an open differential though. The only way to find out is to open her up and count the teeth on the ring and pinnion.

 

[firstgear]

56-62 non-positraction units had part number 3725899 and part number 3789812 was used for a positraction rear end according to my book. I cannot find out what the numbers means because the BB is not the two letter code to determine what the car had in it (eg. in 1960 AH was a manual with an open differential and a 3.70 ratio and AP was a 4.11 positraction unit.) The rear end has probably been blown up sometime in it's life and someone replaced the center chunk with one found out of a junkyard that was used on another GM model. I think my 1961 had a BB code on it bc the differential was not a numbers matching part and it was a 3.36. I'm sure that it is an open differential though. The only way to find out is to open her up and count the teeth on the ring and pinnion.

you know, I was turning the drums and it seemed to me that when I did that, for one revolution of the drum, the pinion turned about 1.6 times or so...that doesn't make any sense does it? am I missing something? what did I do wrong?

 

[JohnZ]

The "BB" stamp indicates that the pumpkin is from a passenger car, cast May 23, 1963 and assembled May 29, 1963 - don't have a chart for those ratio codes. Put it in neutral, jack up the rear end, mark the rear U-joint and both tires; turn both tires one complete revolution and count the revolutions of the U-joint. Three is a 3.08, 3-1/3 is a 3.36, 3-1/2 is a 3.55, 3-3/4 is a 3.70, etc.

 

[firstgear]

The "BB" stamp indicates that the pumpkin is from a passenger car, cast May 23, 1963 and assembled May 29, 1963 - don't have a chart for those ratio codes. Put it in neutral, jack up the rear end, mark the rear U-joint and both tires; turn both tires one complete revolution and count the revolutions of the U-joint. Three is a 3.08, 3-1/3 is a 3.36, 3-1/2 is a 3.55, 3-3/4 is a 3.70, etc.

I turned one wheel drum one turn and the u joint turned about 1.6 revolutions....can that be right or did I do something wrong????? if I turned BOTH wheels would I have gotten 3.3 revs?

 

[JohnZ]

I turned one wheel drum one turn and the u joint turned about 1.6 revolutions....can that be right or did I do something wrong????? if I turned BOTH wheels would I have gotten 3.3 revs?

Yes, you would; there's only a small difference in measured rotation, however, between the 3.08 and 3.36, and turning both wheels to get full pinion rotation will provide a more accurate measurement.