Flawed test? What gears have I?

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bighammer

bighammer

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I want to find out what gears my 8 3/4 has... So I marked the driveshaft and the right rear wheel. I carefully rotated the tire one full revolution. The driveline rotated just under 1 1/2 times. I checked it 3 times. What the heck ? Makes no sense.

Does it matter that the car is on jack stands? Or does it matter which way to rotate the tire?

What the heck is wrong here?? I'm assuming the car has to be on the ground... Is that the case?

Please try not to make me feel any more ignorant than I already feel :-/

OKAY I JUST WENT AND DID THE TEST AGAIN ... Same result
 
doesn't matter you're counting tire vs shaft rotation. It spins the same no matter where or how. Have they been changed? is there a ratio tag on the 3rd member mounting bolt (normally mid way on right side)
 
bighammer said:
I want to find out what gears my 8 3/4 has... So I marked the driveshaft and the right rear wheel. I carefully rotated the tire one full revolution. The driveline rotated just under 1 1/2 times. I checked it 3 times. What the heck ? Makes no sense.

Does it matter that the car is on jack stands? Or does it matter which way to rotate the tire?

What the heck is wrong here?? I'm assuming the car has to be on the ground... Is that the case?

Please try not to make me feel any more ignorant than I already feel :-/

OKAY I JUST WENT AND DID THE TEST AGAIN ... Same result
Click to expand...

If you have an open diff which you must have then the ratio is really double because your turning the spider gears. You must have 2.93's
With an open diff one wheel can stay on the ground for the test.
 
I believe you have a open carrier (non-suregrip). The other tire was probably rotating in the opposite direction during you test. Either get someone to hold the other tire still while testing or lower one side of the car to hold one tire still. If everthing rotated perfectly, you'd have a two gear in it, but the only way to tell for sure is to hold one side still while testing.
 
OldmanRick said:
I believe you have a open carrier (non-suregrip). The other tire was probably rotating in the opposite direction during you test. Either get someone to hold the other tire still while testing or lower one side of the car to hold one tire still. If everthing rotated perfectly, you'd have a two gear in it, but the only way to tell for sure is to hold one side still while testing.
Click to expand...

While doing this with an open diff, the tire which is spinning (while one is held) turns 2 times as fast as its normal speed, due to the spider gearset multiplying rpm. Therefore, if both tires turned equally, your driveshaft would turn 3 times. You have either a 2.93 (I think that is right number) or 3.23 ratio. Try to be more accurate to find out exactly. With an open diff, if you spin only one tire, that tire is actually going twice as fast as your speedo says.
 
Thanks fellas, looks like I have the 2.76 gears :-( I was hoping for 3.??

That is unless someone has swapped the gears, which I doubt as I am the 3rd owner of the car and it has remained mostly stock. Which leads me to another question...

If I was able to locate one, is a Sure Grip a bolt in replacement for my third member? And if so, will it come complete, as a chunk (as I have heard it referred to as) with the ring and pinion gears? Hopefully with the lower gears.

And if so, how can I identify the gear ratio in a third member that is loose from the car?

Many thanks to you guys.

Mark
 

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Or if not stamped divide the number of teeth on the ring gear by the number of teeth on the pinion gear.

41 ring / 10 pinion = 4.10

You can get a sure grip carrier alone or find one as an assembled 3rd member with the gear ratio of your choice. 3.23 is common 3.55 less common and even less common from there.
 
A sure-grip is the type of carrier within the 3rd member. You either have an open carrier (like yours) or you have a sure-grip. Like Rocky said you can buy just a sure-grip but you'll have to use your gears or you can buy a complete 3rd member with lower gears and a sure-grip. If you've never set up gears you'd be best off buying a complete 3rd member IMO. Their not cheap but if you've never set one up having it done by a professional isn't cheap either.
 
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