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8 in rear end ratio

T

Tony R

Member
how do I tell what the ratio is. I turned the wheel one full revolution and the yolk turned 1 1/2 times. What is the ratio or am I missing something?
 
you can check your rear diff tag if its still there and that will tell you the ratio. Unless someone changed the gearing along the way, then that wouldnt help at all
 
so by the video I turned the wheel 10 times and got 15 revolutions out of the diff. Does that give me 1.5? That doesnt sound right to me.
 
I'm guessing you have an "open" rear end. You've got to keep the other axle stationary when you rotate the "driven" one to get accurate results. Also, make sure you are making marks some way to accurately measure the rotations. Eye balling it won't cut it.
 
the one axle is not turning. I am using the hole on the axle in between the wheel studs and have a zip tie on one of the u-joint brackets. They both start at 12:00 position and I make a tally every time they reach the same spot. I would say I am pretty accurate.
 
Well I'm not sure what you've got going on there then but something isn't right. You're coming up with about half what I would have expect for a ratio. With an open rear, you turn the driven axle (wheel) twice and measure the rotation of the pinion to get the ratio. Two wheels turns should get you a bit more than two and half pinion spins in most case (.270 gear). That's pretty much what almost every stock open rear came from the factory with anyway.
 
Open rear, turn wheel twice and count driveshaft rotations. I'm guessing you meant 1 1/2 and not 1 1/12. This would yield 3 driveshaft rotations on 2 wheel turns (open rear). 3.00 gear ratio is what you'll come up with. I'd guess it's a stock gear and not the 3.00 but you need to count teeth to find out for sure.
 
no telling if it was stock. This is an A code V8 car which if I am correct was supposed to have a 4BBL carb but it had a 2BBL.
 
sorry that was a typo. It is 1 1/2. I am still trying to get used to this new keyboard. Turn wheel 1 time I get 1 1/2 and two wheel turns would get me 3 revolutions.
 
Only a locking rear end would give you a correct count of revolution ratio, and even so, both tires have to be off the ground. For open rear ends, double the ratio to get the rear end gear ratio.

Some rear ends are 2.80:1 and a single turn of the drive-shaft isn't enough. I typically use 10 turns and count the number of wheel revolutions and adjust accordingly.
 
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