1.9 axle ratio???? HELP PLEASE!

[motorbreath]

I raised the rear of my truck off the ground yesterday. Rotated the tire one full turn to find that the drive shaft only turned about 1.8- 1.9 times. Shouldn't it be 3.42 or 3.73 times????! What is going on? It's a 1999 obs Yukon. I bought a little over a year ago having tranny issues. Running 35s and was thinking of re gearing differential but why is it so high???

 

[ccapehartusarmyINF.(ret)]

okay you gotta reach under there and turn yer drive shaft and watch how many times yer wheel rotates

 

[motorbreath]

Thanks for the response friend, but it would help a little bit more if you actually read my post hehe

 

[drakon543]

He is basically stating you did the process backwards.

 

[drakon543]

You can find your gear ratio easily with this method. All you need is a jack, some jackstands, and knowing how to count helps too.

You're going to have to put the car in nuetral or out of gear, so safety first! Do this on level ground, and be sure and chock the front wheels so the car can't move. It helps to have someone there in the car just in case...

First, do you have a posi or limited slip rear? If you're not sure, just jack up the rear so both tires are off the ground and put your jackstands under the axle. Now turn one of the tires. If the other tire turns the same way or doesn't turn at all, you should have a posi or limited slip. If the tire turns opposite of the way the first tire spins, then it's probably an open rear end.

If you have a car with a posi or limited slip rear, jack up the car and get both rear tires off the ground. Now put your jackstands under the axle. Make a line on the pinion yoke and onto the rear end with chalk or a grease pencil. Do the same to the tire on the car, so you can see when the tire has rotated exactly one turn.

Now count the number of turns of the driveshaft that it takes (use your chalk marks) to make the rear tire turn one complete rotation. (Transmission needs to be in nuetral or out of gear.)

If your car has an open rear, jack up only one rear tire and leave the other on the ground. Now put a jackstand under the lifted side. Turn the tire and again count the number of turns of the driveshaft, but this time you must turn the tire two full rotations.

So:

Posi: Jack both wheels off the ground. Turn one wheel 1 complete turn.

- Count the turns on the drive shaft.

Non-posi: Jack one wheel off the ground. Turn the wheel 2 complete turns.

- Count the turns on the drive shaft.

If it takes about 2 and three-quarters turns, it's around a 2.73 gear ratio. If it's a little more than 3, you have 3.08s. If it takes about 3 and a quarter turns of the driveshaft, you have 3.23 or 3.25 gears. Very close to 3 and three-quarter turns, 3.70 or 3.73 gears. This method won't work very well on a posi that's worn-out and won't spin both tires equally.

This method is very handy when looking through junkyards or swap meets. It's good to be able to figure what gear ratio you have without tearing anything apart.

This is a quick and easy way to tell what gear ratio is in your rearend. You might not be able to tell exactly what gear you have, but you'll be very close.

If you want to be accurate, then count the teeth.

If you have the rearend opened up where you can see the gears, count the teeth on the ring and pinion. Divide the ring teeth number by the pinion teeth number.

Example: 41 teeth on the ring and 10 teeth on the pinion = 4.10 gear ratio...

 

[motorbreath]

He is basically stating you did the process backwards.

How so? I simply counted how many times the drive shaft rotated per wheel rotation.... 1.9 driveshaft rotation = 1 wheel rotation... ORRRRR 1 driveshaft rotation = .526 wheel rotation. Either way you figure it, its not 3.42 or 3.73.... Anyone out there who can comprehend??

 

[motorbreath]

You can find your gear ratio easily with this method. All you need is a jack, some jackstands, and knowing how to count helps too.

You're going to have to put the car in nuetral or out of gear, so safety first! Do this on level ground, and be sure and chock the front wheels so the car can't move. It helps to have someone there in the car just in case...

First, do you have a posi or limited slip rear? If you're not sure, just jack up the rear so both tires are off the ground and put your jackstands under the axle. Now turn one of the tires. If the other tire turns the same way or doesn't turn at all, you should have a posi or limited slip. If the tire turns opposite of the way the first tire spins, then it's probably an open rear end.

If you have a car with a posi or limited slip rear, jack up the car and get both rear tires off the ground. Now put your jackstands under the axle. Make a line on the pinion yoke and onto the rear end with chalk or a grease pencil. Do the same to the tire on the car, so you can see when the tire has rotated exactly one turn.

Now count the number of turns of the driveshaft that it takes (use your chalk marks) to make the rear tire turn one complete rotation. (Transmission needs to be in nuetral or out of gear.)

If your car has an open rear, jack up only one rear tire and leave the other on the ground. Now put a jackstand under the lifted side. Turn the tire and again count the number of turns of the driveshaft, but this time you must turn the tire two full rotations.

So:

Posi: Jack both wheels off the ground. Turn one wheel 1 complete turn.

- Count the turns on the drive shaft.

Non-posi: Jack one wheel off the ground. Turn the wheel 2 complete turns.

- Count the turns on the drive shaft.

If it takes about 2 and three-quarters turns, it's around a 2.73 gear ratio. If it's a little more than 3, you have 3.08s. If it takes about 3 and a quarter turns of the driveshaft, you have 3.23 or 3.25 gears. Very close to 3 and three-quarter turns, 3.70 or 3.73 gears. This method won't work very well on a posi that's worn-out and won't spin both tires equally.

This method is very handy when looking through junkyards or swap meets. It's good to be able to figure what gear ratio you have without tearing anything apart.

This is a quick and easy way to tell what gear ratio is in your rearend. You might not be able to tell exactly what gear you have, but you'll be very close.

If you want to be accurate, then count the teeth.

If you have the rearend opened up where you can see the gears, count the teeth on the ring and pinion. Divide the ring teeth number by the pinion teeth number.

Example: 41 teeth on the ring and 10 teeth on the pinion = 4.10 gear ratio...

Thanks bud, but if you read my post you will see that Ive already got the determining method figured out. Im trying to figure out why its only 1.9 instead of one the stock ratios.... What the purpose of such an awkward truck gear would be... where it may have come from....etc

 

[drakon543]

If you had 1.9 gear ratio the truck would barely get out of its own way. You probably have a non posi rear. And if you read what i posted your supposed to spin the driveshaft not the tire. If you have a non posi unit and your spinning one of the tires with both tires off the ground your not transfering the rotation of the tires properly. I dont mean to be a dick but you state you have the method figured out already but your coming up with 1.9 gear ratio which besides the truck would be gutless as a MF i think its also probably impossible. Im not going to spend my morning to see if you can even buy gearing in that ratio but ive never heard of anything that low. So it seems obvious to me that the method your using is incorrect and maybe you should try a different method or alter your method to incorporate some of the good information i have posted about rear end gearing.

 

[motorbreath]

If you had 1.9 gear ratio the truck would barely get out of its own way. You probably have a non posi rear. And if you read what i posted your supposed to spin the driveshaft not the tire. If you have a non posi unit and your spinning one of the tires with both tires off the ground your not transfering the rotation of the tires properly. I dont mean to be a dick but you state you have the method figured out already but your coming up with 1.9 gear ratio which besides the truck would be gutless as a MF i think its also probably impossible. Im not going to spend my morning to see if you can even buy gearing in that ratio but ive never heard of anything that low. So it seems obvious to me that the method your using is incorrect and maybe you should try a different method or alter your method to incorporate some of the good information i have posted about rear end gearing.

Well Im sorry to debunk your theory, but the truck DOES actually move decent (Although not as well as it should).... I have done it both ways (turn driveshaft/turn tire) and the result is the same, so I don't mean to be a dick, but you obviously aren't knowledgable enough to know that your information isn't as accurate as you think it is. Thanks for your attempt tho. My guess is that for whatever reason, someone decided to put a retarded gear in the rearend at sometime... looks like ill be visiting the salvage yard.. the terrible gear probably explains my transmission problems

 

[drakon543]

My bad obviously someone with more money than brains paid a machine shop to custom cut them a set of rear end gearing so they could have a 1.9 ratio.....
Anyway since your too intelligent to have read the information i posted fully ill make one final post and i wont be visiting this thread again. If you had a 1.9 your truck would be gutless not decent but gutless. In my info post it was stated if you didnt have a posi rear you would make 2 full rotations rather than 1 rotation which would put yout gearing in the range of a 3.73 which would be common and allow the truck to move decent as you described. Im not sure which rears came stock with the stamp on the ring gear probably most if not all but you should be able to pop the cover off and look for a stamping on the ring gear that will tell you what the gearing is. If this is in reference to the truck in your profile pic im not sure what tire size your running but you probably want to find a 4.10 rear.