Differential ring verification
Thread Starter
Pro
Joined: Oct 2006
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From: Bonheiden Belgium Europe
Differential ring verification
How can you determine if the ring and pinion are correct for the housing code of a rear end.
I have an 1965 differntial with code AP 12 21 64 on the housing which is a 4.11 I believe.
On the ring I can find several numbers one set is 32-4-63 the ring has 32 tooth.
Is this the correct ring for 4.11?
I also have a 71 rear end which reads LR which is a 3.36 I believe. the ring reads 373590 1 1:37 GM and has 37 tooth is the correct ring for a 3.36?
I have an 1965 differntial with code AP 12 21 64 on the housing which is a 4.11 I believe.
On the ring I can find several numbers one set is 32-4-63 the ring has 32 tooth.
Is this the correct ring for 4.11?
I also have a 71 rear end which reads LR which is a 3.36 I believe. the ring reads 373590 1 1:37 GM and has 37 tooth is the correct ring for a 3.36?
Melting Slicks
Joined: Aug 2004
Posts: 2,062
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From: Sun Prairie WI
Ring and pinion gears are (were) as assembly. Differential carriers may have had internals changed over the years, so the ratio codes may not be meaningful. What will work is counting ring teeth and dividing by pinion teeth. A 4.11:1 has 37 ring/9 pinion = 4.11.
If you have the 32 tooth ring (& 9T pinion) as appears in your post, that's a 3.55:1. (That's the only application for 32 tooth ring).
37 tooth ring gears, on the other hand, were used with 9, 10, 11 or 12 tooth pinions, so the ratio achieved could be 4.11, 3.70, 3.36 or 3.08:1 respectively.
If you have the 32 tooth ring (& 9T pinion) as appears in your post, that's a 3.55:1. (That's the only application for 32 tooth ring).
37 tooth ring gears, on the other hand, were used with 9, 10, 11 or 12 tooth pinions, so the ratio achieved could be 4.11, 3.70, 3.36 or 3.08:1 respectively.
Thread Starter
Pro
Joined: Oct 2006
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From: Bonheiden Belgium Europe
Thx for the info 
You are right I counted them with the 32 tooth ring it has 9 tooth on the pinion so a 3.55.
Code on the housing reads AP which according the Corvette Chassis and restoration guide is a 4.11 from a 327.
Someone in its 42 year life must have change them I guess
Should have done this home work before I bought the 71 BB 3.36 (37/9) rear end.
Not much difference between a 3.55 and a 3.36.
You are right I counted them with the 32 tooth ring it has 9 tooth on the pinion so a 3.55.
Code on the housing reads AP which according the Corvette Chassis and restoration guide is a 4.11 from a 327.
Someone in its 42 year life must have change them I guess
Should have done this home work before I bought the 71 BB 3.36 (37/9) rear end.
Not much difference between a 3.55 and a 3.36.
Team Owner
Joined: Oct 2000
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