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4/17/17 7:10pm - Original Message: 'Differential Build Dates Question'
Ole Biker Gold Member
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Monongahela, PA - USA

Vette(s):
1969 Corvette Coupe. 427/435 4 speed factory installed side pipes. Verified Numbers Matching.

Joined: 7/5/2016
Posts: 67
Hello,

I have the casting number from the differential case and the stamped code for the gear ratio and assembly build for my 1969 Vette.

The casting on the case is  B 24 9
The stamped code on the bottom of the cover is  1AZ 9 2 69

If I am assuming correctly the cast number refers to February 24, 1969 and the stamped code refers to late 1969 Heavy Duty 3:55 ratio September 2nd 1969 build.

Am I correct in my assumptions?  If so, this further confirms the numbers matching aspect of the entire differential to the build date of the rest of the car.

Thanks In Advance For Any Replies!
Mike C



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4/17/17 9:18pm - Reply: 'Re: Differential Build Dates Question'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
Looks right to me. HD 3:55 posi, 427, close enough build date for the car. Thumbs Up
The casting date is for the date the actual diff housing was cast, and the stamped alpha-numeric info is the date the diff was actually assembled. 

|UPDATED|4/17/2017 7:18:23 PM (AZT)|/UPDATED|


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Joel Adams
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4/17/17 9:25pm - Reply: 'Re: Differential Build Dates Question'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 398
Was the HD diff and option or standard?  First time I've heard of it.

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1973 L-82 4 spd

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4/18/17 6:25am - Reply: 'Re: Differential Build Dates Question'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
HD diff had the bolt on, threaded style yokes for the halfshafts, instead of the u-bolt/nuts. All big blocks had the HD diff.

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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4/18/17 7:06am - Reply: 'Re: Differential Build Dates Question'
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.

Joined: 7/9/2003
Posts: 398
Thanks. Never too old to learn.   Thumbs Up

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1973 L-82 4 spd

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4/18/17 1:46pm - Reply: 'Re: Differential Build Dates Question'
Ole Biker Gold Member
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Monongahela, PA - USA

Vette(s):
1969 Corvette Coupe. 427/435 4 speed factory installed side pipes. Verified Numbers Matching.

Joined: 7/5/2016
Posts: 67
Hello, I tried posting a picture of the diff but not successful

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4/18/17 9:53pm - Reply: 'Re: Differential Build Dates Question'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19458
This one?




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Joel Adams
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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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4/26/17 4:04pm - Reply: 'Re: Differential Build Dates Question'
Ole Biker Gold Member
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Monongahela, PA - USA

Vette(s):
1969 Corvette Coupe. 427/435 4 speed factory installed side pipes. Verified Numbers Matching.

Joined: 7/5/2016
Posts: 67
Hello,

Trying again to post picture of casting on housing,

February 24, 1969


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4/26/17 4:07pm - Reply: 'Re: Differential Build Dates Question'
Ole Biker Gold Member
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Monongahela, PA - USA

Vette(s):
1969 Corvette Coupe. 427/435 4 speed factory installed side pipes. Verified Numbers Matching.

Joined: 7/5/2016
Posts: 67
Stamped code at bottom of housing,

Heavy Duty 3:55 ratio September 2nd, 1969



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4/26/17 8:07pm - Reply: 'Re: Differential Build Dates Question'
gtr1999
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Wallingford, CT - USA

Vette(s):
1969 350 4 spd drop top 1972 350 auto coupe

Joined: 5/2/2016
Posts: 57
As Adam mentioned the only difference is with the axle yokes. In all reality I have never seen a yoke break at that point. I have seen rebuilt axles break, twisted splines, worn axle faces but never a broken yoke. Many times customers want to upgrade to the "HD" axles but don't realize how expensive a used set of caps are, about $125-150 for used GM, which are the best.
 
Axle endplay is more important in my opinion. I set my diffs up for 005-007 endplay. You might want to shoot some cast blast on the cover bolts or they will rust up on you.
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4/27/17 9:50am - Reply: 'Re: Differential Build Dates Question'
Ole Biker Gold Member
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Monongahela, PA - USA

Vette(s):
1969 Corvette Coupe. 427/435 4 speed factory installed side pipes. Verified Numbers Matching.

Joined: 7/5/2016
Posts: 67
gtr1999 said: As Adam mentioned the only difference is with the axle yokes. In all reality I have never seen a yoke break at that point. I have seen rebuilt axles break, twisted splines, worn axle faces but never a broken yoke. Many times customers want to upgrade to the "HD" axles but don't realize how expensive a used set of caps are, about $125-150 for used GM, which are the best.
 
Axle endplay is more important in my opinion. I set my diffs up for 005-007 endplay. You might want to shoot some cast blast on the cover bolts or they will rust up on you.


Hello,

As Bair's rebuilt the differential I assume it is set up in spec.

Good idea on the bolt heads,

Thanks!
Mike C


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