Gear ratio question.

[Reziel_1983]

So I did the "tape the driveshaft and spin the tire" trick to try to figure out my gear ratio in my 83. But when I spun the tire the drive shaft only turned once and almost once again. Would this mean I have somewhere between a 1.75-2.00:1 gear ratio? I've never heard of one being like that...

[bigwheel15]

How many times did u spin the tire? I was told mark the driveshaft, spin the tire twice and count the driveshaft revolutions.
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[Reziel_1983]

I did only spin the tire once. So you spin the tire twice? I've always heard that the more times you spin it the more accurate you will get but I thought you can spin it once and get a rough estimate.

[bigwheel15]

I used the spin twice method to find my gear ratio. Try it and see what you come up with.
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[Reziel_1983]

I've also heard that you can turn the driveshaft and count how many times it takes for the wheel to spin.. would that give me the same answer?

[Keith Seymore]

Originally Posted by Reziel_1983

I've also heard that you can turn the driveshaft and count how many times it takes for the wheel to spin.. would that give me the same answer?

No - that would give you the reciprocal of the answer.



K

[Firebirdjones]

When's the last time the gear oil was changed? I'm betting it could use it

Drop the cover and change the oil, while you're at it, count the teeth and divide, or since most gear sets have the tooth count engraved on the ring gear, divide the pinion into the ring gear and see what you have.

[Rich84]

Probably 2:56 or 2:73...I think that's what all the 305s came with...then again could have anything after almost 30 years.
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[Reziel_1983]

Originally Posted by Firebirdjones

When's the last time the gear oil was changed? I'm betting it could use it

Drop the cover and change the oil, while you're at it, count the teeth and divide, or since most gear sets have the tooth count engraved on the ring gear, divide the pinion into the ring gear and see what you have.

I'll probably do this. Probably needs to have the oil changed anyway. I've never changed it and I've had the truck for years, lol.

[wilkin250r]

You're spinning one tire, and the other tire is stationary, right? Is it still on the ground?

It's understandable that you're confused, you're only getting half your answer. With the way the differential works, you need to spin your tire TWICE and count the driveshaft rotations.

Because your other wheel is stationary, your ring gear is only turning half the rotations that the tire is, which means the driveshaft is also spinning half as many rotations as it should. If your turning the tire once and you get almost two rotations of the driveshaft, it sounds like you may have a 3.73