Help! decode rear-end
Thread Starter
Pro
Joined: Jun 2007
Posts: 688
Likes: 1
From: Stevens Point WI
Help! decode rear-end
I have the cover off the rear-end for my vette and I need to know what the ratio is for sure.
I counted the teeth on the larger gear and there are 37
And on that gear it says
3733908 9-37 GM1 65 1A
I think they might be 3.90?
I am going with a muncie m20 and a 427 if they are 3.90 that would be allot going down the road at 70 mph huh? About 4200+ ?
Any help would be great.
I counted the teeth on the larger gear and there are 37
And on that gear it says
3733908 9-37 GM1 65 1A
I think they might be 3.90?
I am going with a muncie m20 and a 427 if they are 3.90 that would be allot going down the road at 70 mph huh? About 4200+ ?
Any help would be great.
Thread Starter
Pro
Joined: Jun 2007
Posts: 688
Likes: 1
From: Stevens Point WI
The rear-end is not from my 69 vette but a donor out of a 66 vette that was used in autocross events
The rear bottom reads FB 66
so originally it was a BB 427 4:11:1 out of a 66 vette
the guy I bought it from could not tell me for sure what gears where in it now.
Anyone have a way to decode that ring gear number?
The rear bottom reads FB 66
so originally it was a BB 427 4:11:1 out of a 66 vette
the guy I bought it from could not tell me for sure what gears where in it now.
Anyone have a way to decode that ring gear number?
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
You can get a pretty good idea by just putting a mark on the input and output shafts and tuning the input shaft. If it takes a little more than 4 turns of the input to get 1 turn of the output you most likely have a 4.11
I think a 4.11 is too much for the highway unless you have an overdrive transmission. I'm going to put 4.10 gears in my diff but only because I'm using a 6-speed trans with overdrive in the top 2 gears.
Rick B.
I think a 4.11 is too much for the highway unless you have an overdrive transmission. I'm going to put 4.10 gears in my diff but only because I'm using a 6-speed trans with overdrive in the top 2 gears.
Rick B.
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Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
The numbers you listed are definitly for a 4.11. The ring gear is 3733908 and the pinion should be 3885945. A 3.70 gear should have 3737957 on the ring gear. See if you can count the teeth on the pinion. For a 4.11 it should be 9 and a 3.70 should be 12.
Thread Starter
Pro
Joined: Jun 2007
Posts: 688
Likes: 1
From: Stevens Point WI
OK 4:11:1
With a 450-500hp motor and a m20 would the 3:55:1 be the way to go for all around use?
I am sure how light this car is it would still spin the tires all day
I am looking at a 1-3 hour cruise for a overnight ect... would it overheat going 70-75 down the highway?
I plan on a aluminum radiator and dual fans
Also side exauhst
With a 450-500hp motor and a m20 would the 3:55:1 be the way to go for all around use?
I am sure how light this car is it would still spin the tires all day
I am looking at a 1-3 hour cruise for a overnight ect... would it overheat going 70-75 down the highway?
I plan on a aluminum radiator and dual fans
Also side exauhst
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Back in the 60 and 70s 3.55 to 4.11 gears were normal and the ygot driven all the time. 3.55 is a good combo gear for in town and highway. I ran a 4.11 gear with my M20 and it was steep on the highway. The 3.70s were better but a 3.55 would be even better. inow run an OD with a 3.70 gear. The OD brings it down to a 2.51 gear. You should not overheat providing everything in the cooling system is in good shape.
