Topic: How to figure out gear ratio
in Forum: C3 Driveline Components
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From what I've read, the differential case on my 72 vette should have a production code stamped on it. The first two letters indicate the gear ratio. For example, AA would indicate 3.55:1.
From under the car, I've tried to find the production code, but I don't see it.
Can anyone tell me where it's located on the differential case? (Front, back, left, right, etc.)
Thanks!
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Lifetime MemberDuncanville, TX - USA
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Mounds View, MN - USA
Joined: 5/24/2007
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Vette(s): 70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe
Then, since your car is almost 40 years old, you might want to count the ratio anyway. Jack up both sides of the rear and make sure both wheels turn together. Then turn the wheels one turn, and count how many turns the driveshaft turns.
Larry
Larry
You can multiply miles per hour times 1000 and divide by the engine RPM. For a 3.08:1 the ratio is 25.6, for 3.36:1 is 23.1, for 3.55:1 is 22.2, for 3.70:1 is 21.3, for 4.11:1 is 19.2, and for 4.56;1 is 17.0. Do it at different speeds and in different gears and you should get a pretty good average.
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Mounds View, MN - USA
Joined: 5/24/2007
Posts: 1031
Vette(s): 70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe
That method depends on tire size. The only correct way is to count the turns.
Larry
Larry
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Flat Rock, MI - USA
Joined: 4/4/2010
Posts: 14
Vette(s): L48 coupe, red on red.
I tried Larry's post (marked rotor and drive shaft) and it came out to be 3 and a 1/4 turns. The 73 vette did have a 3:26. The AW273E2 on the rear comes up in reference book as a 3:08. The build sheet for the motor has major upgrades but I have no paperwork for anything else. Think it could be a gear swap?
in Forum: C3 Driveline Components
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