77 4 spd trans + Diff ID Help
Thread Starter
Instructor
Joined: May 2005
Posts: 222
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77 4 spd trans + Diff ID Help
I bought my 77 vette last spring. MY differential is out now. I counted my ring a pinion teeth and have a 3.08 final drive ratio. I understand the stock L48 should have a 3.70 ratio. Is this correct? The numbers on the diff are: OA 23 3 W 7E 1 and: 8 gm 3899143 and: 38713 5. I thought it was lacking in acceleration. Before I invest in a 3.70 gear set, I wanted to make sure I have the stock 4 spd trans. The numbers on the trans are:304065903 W.G. DIV. FPC 2 and: 5.11.76.
Any help would be appreciated. I'm a little disappointed but at least the cars performance is starting to make some sense.
Any help would be appreciated. I'm a little disappointed but at least the cars performance is starting to make some sense.
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
Originally Posted by 77vettejeff
additional codes on the left side of the case are: WH2362 and: 17S402430. I can't seem to find any on-line resources for identification 
The WH2362 is the Borg Warner production code and indicates the following:
W=B/W
H=month of production
23= day of month
6=model year
2= ratio suffix
So you've got a B/W M21 close ratio 4-speed date coded May 23, 1976. The VIN 2430 indicates an early production 77 model.
Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
Originally Posted by 77vettejeff
I bought my 77 vette last spring. MY differential is out now. I counted my ring a pinion teeth and have a 3.08 final drive ratio. I understand the stock L48 should have a 3.70 ratio. Is this correct? The numbers on the diff are: OA 23 3 W 7E 1 and: 8 gm 3899143 and: 38713 5.
Any help would be appreciated. I'm a little disappointed but at least the cars performance is starting to make some sense.
Any help would be appreciated. I'm a little disappointed but at least the cars performance is starting to make some sense.
The OA 233 W 7E 1 code indicates a 3:08 axle ratio (OA) assembled the 233 day of 1977 at the Warren assembly plant (W) on the 1st shift (7E 1). The E indicates an Eaton assembled positraction assembly.
The 233 is a Julian date code which translates into August of 77...consistent with your VIN assembly date.
So...your vehicle was built with the economy axle ratio...base was the 3.36. The 3.70 was reserved for the L82 4 speed.
Racer
Joined: Dec 2004
Posts: 379
Likes: 0
From: Fairfield Texas
The aforementioned close ratio trans. has a 2:20 ratio low gear as
opposed to the 2:54 in the wide ratio thus contributing even more to
Your less than stellar low gear performance.The C/R trans. with a 3:70
rear on the other hand makes for a nice combination.I have this combo
in a 79 L 82 and although its not all that fast it is enjoyable to drive
because when going through the gears You can keep the revs up
and it feels and sounds good. Just My .02 cents worth.
opposed to the 2:54 in the wide ratio thus contributing even more to
Your less than stellar low gear performance.The C/R trans. with a 3:70
rear on the other hand makes for a nice combination.I have this combo
in a 79 L 82 and although its not all that fast it is enjoyable to drive
because when going through the gears You can keep the revs up
and it feels and sounds good. Just My .02 cents worth.
Tech Contributor
Joined: Aug 1999
Posts: 15,135
Likes: 3,939
From: Connecticut, USA
Yes the 370 was the optional L-82 gear. typically the L-48 had the 336 with 4 spd and 308 with auto. Did you find the stamping on the ring gear?
You can run the 370 or 373 gear with a WR M-20 or M-21 CR. The acceleration w/M-20 will be better in 1st gear but the CR is better suited for road racing applications where you want to the RPM band closer. For street use the M-20 or a 5-spd would be great.
You can run the 370 or 373 gear with a WR M-20 or M-21 CR. The acceleration w/M-20 will be better in 1st gear but the CR is better suited for road racing applications where you want to the RPM band closer. For street use the M-20 or a 5-spd would be great.
Racer
Joined: Dec 2004
Posts: 379
Likes: 0
From: Fairfield Texas
Originally Posted by 77vettejeff
great feedback, thanks to all.
Hey Chevylit, are you running around 3500 rpm at 65 mph?
Hey Chevylit, are you running around 3500 rpm at 65 mph?
about the only thing thats not too swell about having a 3:70 rear.Guess
thats why there's so much swapping to overdrive transmissions.
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Le Mans Master
Joined: Sep 2002
Posts: 5,235
Likes: 898
From: Myrtle Beach SC
Originally Posted by 77vettejeff
great feedback, thanks to all.
Hey Chevylit, are you running around 3500 rpm at 65 mph?
Hey Chevylit, are you running around 3500 rpm at 65 mph?
Racer
Joined: Dec 2004
Posts: 379
Likes: 0
From: Fairfield Texas
Originally Posted by hunt4cleanair
You don't by any chance have a build sheet or window sticker do you? I'm wondering what the broadcast code printed on the paperwork showed?
to man but not one thing for My 79 L82 4 speed.
