decoding rear differential - Impala Tech
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post #1 of 9 (permalink) Old 11-13-2013, 10:23 AM Thread Starter
 
 
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decoding rear differential

have 64 ss 409 dual quad. data plate confirms everything is correct from the vinyl interior down to the trans. when i got to the rear end stamp it was AB102. I looked up ab and found 336 gears non posi unless the 102 changes that. I feel that someone put these after it left the factory because this is a non power steering non power brake. i would have guessed this car would have had a stronger gear like a 411. can anybody help me decode this? also the tranny is a four speed. I can not believe this car came out of the factory without a posi.
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post #2 of 9 (permalink) Old 11-13-2013, 01:48 PM
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Welcome to the Team Roger!

PosiTraction was a very rare option back in 1964. Any Hotchkiss limited slip clutch style case will have a big "P" cast onto the drivers side of the case, and a price tag of close to a $2,000 or more. This is because early straight axle Corvette owners think that their 1953-'62 'vette should have a posi also; but there were just so few made. They will pay through the nose for a P case, driving up the price of those found on e-Bay to the point were it costs as much as a new Impala project car.

Additionally; that same Salisbury rear end designed and built to last a life time in a car that was powered by a 235 six (that was used in all Chevy's back before the first V-8 came out in 1955) is not going to last long behind a high horse V-8. That is why Chevy dropped that rear end in 1965 and went with a Spicer rear end made with stronger components.

Those rears broke so frequently that having one replaced is not only a common occurrence, but expected when found in a high performance car with a manual tranny.

Big Dave

Last edited by Big Dave; 11-13-2013 at 03:07 PM.
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post #3 of 9 (permalink) Old 11-13-2013, 02:26 PM Thread Starter
 
 
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decoding 64 rear end

thank you dave. do you think i was correct on decoding the stamp number ab 102 as a 336 and do you know what the 102 stands for
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post #4 of 9 (permalink) Old 11-13-2013, 03:34 PM
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The 102 denotes the calendar day of the physical year that the rear end was built by Detroit Gear. That rear end is out of a passenger car (B-body) that had a six cylinder and a PowerGlide originaly. This assumes the date code confirms it was cast in 1964. If not the AB code will indicate a gear ratio other than a 3.36:1, as the AB code was used frequently.

Big Dave
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post #5 of 9 (permalink) Old 11-13-2013, 07:51 PM Thread Starter
 
 
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decoding 64 rear end

thank you again. I found a site that said the ab (336) was only coded that way from1958 to 1964 and you werecorrect that they were on the smaller blocks. I also found a site that said they made a posi 336 but i could not find a year range. the casing this 336 is in i believe ia a 12 bolt and on the fill plug there is ring that says positraction. so the rear end could be out of another year. it is funny because everything appears orignal and the mileage is said to be low, but it must have sat on concrete or some surface that allowed moisture up underneath which shows in the deteriation of the underneath.
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post #6 of 9 (permalink) Old 11-13-2013, 08:17 PM Thread Starter
 
 
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decoding engine

How about taking a stab at the engine code F1210 QB. i know the qb stands for 409 dual quad. i think the f stands for june and the 12 for the day of the month, but i can not figure the 10
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post #7 of 9 (permalink) Old 11-14-2013, 01:40 AM
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I believe the 12 is December and 10 is the 10th day.
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post #8 of 9 (permalink) Old 11-14-2013, 02:33 PM
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Posi-rear ends for the drop out Chevy came in three styles. The first was the rare X casting used for a few months in 1956 and the balance of 1957. After that they made the thin P casting up until 1962 when they came out with the thick P casting used in 1963-'64. They all inter change as far as bolting a complete rear end into the car but that assumes you have the axles to match the differential as they changed the axles as well as the rear end carrier. The thick casting had an inch wider track rear end, and used 28 spline axles. The thin casting used the older weaker 17 spline axles.

Parts can be swapped internally as I remember it, but I also remember getting a posi rear end where the parts did not interchange because it hit something or wouldn't go back together for some reason that frustrated me at the time. I just can not recall a half century later what stymied me then. I do recall that I gave up on all drop out Chevy rear ends and swapped mine out for a bigger Olds rear end that bolted up in place of the weaker Chevy rear end with very little effort. Prior to the Olds rear I was using the thin P castings with thicker 28 spline axles and cut down Mopar spider gears as they where stronger than the Chevy parts.

The Olds was the last rear end that I ever put under that car as it never broke anything inside the rear end again after the swap. I sold off all three of my old Chevy P case posi units I had along with all of my spare gear sets to other racers and came out ahead cash wise. (If only I had known then what they would sell for now! But that was just one more of many mistakes that I made learning how to hotrod cars by trial and error.)

Big Dave
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post #9 of 9 (permalink) Old 11-16-2013, 04:43 PM
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Quote:
Originally Posted by 64-ss-409-2-4bbl View Post
How about taking a stab at the engine code F1210 QB. i know the qb stands for 409 dual quad. i think the f stands for june and the 12 for the day of the month, but i can not figure the 10
You need to look closer at that stamping. It should read T1210, where the T stands for the Tonawanda engine plant. 1210 means the engine was assembled on Dec 10th.

The 102 stamped in the rear means the rear was assembled on Oct. 2nd. The other side of the case will have the casting date which will end with the year. If the rear is original and was assembled in Oct., the casting date would end in 63. (or 3 depending on where it was built).

Verne
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