determine rear end ratio
Thread Starter
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Freshman User
Joined: Jul 1999
Posts: 44
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determine rear end ratio
Hello
I marked the drive shaft and marked the tire after raising the wheel off the floor. With one turn of the drive shaft the tire only rotates about 7/8 turn. I guess I expected a much higher ratio. What am I doing wrong to get a general idea of what the ratio is? Thanks for any input.
regards,
Fuzz
I marked the drive shaft and marked the tire after raising the wheel off the floor. With one turn of the drive shaft the tire only rotates about 7/8 turn. I guess I expected a much higher ratio. What am I doing wrong to get a general idea of what the ratio is? Thanks for any input.
regards,
Fuzz
Tuned
Joined: Dec 2004
Posts: 340
Likes: 8
From: Rock Hill, SC
That doesn't sound right. If you raise one wheel you multiply what ever shaft revolution it takes to get one tire revolution by 2. Or just turn the shaft until the tire goes around twice. Then you have your answer. I am guessing you have no tag on your diff? They usually have a tag with the ratio marked on it held on by one of the bolts that holds the differential assembly in.
Thread Starter
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Freshman User
Joined: Jul 1999
Posts: 44
Likes: 1
Fuzz
Thanks Red
I went out and did as you said. I come up with Three turns of the shaft to the tires twice. So my ratio must be three. I see in my LMC catalog that a 3.00 was offered so that must be the baby. I have a 67 SWB with a 460 with the Edelbrock performer series manifold and 800cfm carb and use a not to wild comp cam that runs with hydraulic lifters.Last time i looked it cost me 75 cents to pass a car. I guess the rear end ratio is not that bad for the 460 as I can get em baking no problem, but helps when cruising.
Thanks again
Fuzz
I went out and did as you said. I come up with Three turns of the shaft to the tires twice. So my ratio must be three. I see in my LMC catalog that a 3.00 was offered so that must be the baby. I have a 67 SWB with a 460 with the Edelbrock performer series manifold and 800cfm carb and use a not to wild comp cam that runs with hydraulic lifters.Last time i looked it cost me 75 cents to pass a car. I guess the rear end ratio is not that bad for the 460 as I can get em baking no problem, but helps when cruising.
Thanks again
Fuzz
Moderator
Joined: Dec 2003
Posts: 97,590
Likes: 2,008
From: Saskatoon, Saskatchewan
Most of the time on an older vehicle you can bet some wingnut has not put the tag back on after working on it. 
Never did figure out why they think that they are the only ones that will ever need that tag! Seems like it is just too much trouble to simply put it back on. 
Never did figure out why they think that they are the only ones that will ever need that tag! Seems like it is just too much trouble to simply put it back on.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
Likes: 74
From: Creedmoor, North Carolina
I can never remember to jack up one wheel or both wheels, so I learned to push the truck one tire rev. and count the ds revs. That will give you real time info.
You should be looking for a full three turns of the ds for a 3.00 to over four for a 4.11.
In high gear the engine, tranny, & ds all turn the same rpms, it's called 1 to 1. It's the 1 to 1 ratio against the wheel/axle rev. that gives you your rear gear ratio.
hope I got that right
John
You should be looking for a full three turns of the ds for a 3.00 to over four for a 4.11.
In high gear the engine, tranny, & ds all turn the same rpms, it's called 1 to 1. It's the 1 to 1 ratio against the wheel/axle rev. that gives you your rear gear ratio.
hope I got that right
John
