gonna find out my rear end ratio....

[oldblue1968chevy]

i dont have a tag on the diff bolts..

if i take the cover off to read the ring gear..will i be able to find it? or am i better off to spin the whels and count the driveshaft rotations? and how much does it cost to rebuild a rearend? (roughly)

thanks!

[Tx Firefighter]

Pop the cover and read the ring gear. Turn it around until you get to the numbers and wipe the oil off of them. There will be two numbers separated by a colon. Divide the first number by the second and you will have your ratio.

[oldblue1968chevy]

i got 1 tire jacked up (not posi) ok i turn the tire count the driveshaft truns and time that by 2 right?

im confused ima go out there do it and write it down then post it here lol thanks


ok thats what ima do to my donor rearend thanks! will any oil leak out?

[prostreetC-10]

What you do is to turn the pinion yoke (driveline) exactly one time and count how many times the tire goes around. It's actually a pretty darn accurate redneck way of finding the ratio. Chalk or mark the tire somehow.

If it's goes around 3 1/2 times, it's about a 3.50

If it only goes around a little more than 3, it's a 3.07 or 08

I like it when they go around 3 3/4's times cuz that's your 3.73

and so on......

[oldblue1968chevy]

30 56

30 being the tire spins

56 being d shaft


i came up with 3.73 is this correct? thanks goin into the weeds with the snakes to calcualte the other rearend...

[prostreetC-10]

Originally Posted by oldblue1968chevy

30 56

30 being the tire spins

56 being d shaft


i came up with 3.73 is this correct? thanks goin into the weeds with the snakes to calcualte the other rearend...

Not sure K and I know what you are talking about. Just what exactly is the 30 and what is the 56?

[Big-Blue]

Here's a shot of my 4:10 rear end.

The text reads, 7 3 70 DANA 30360 A306 41-10

I am guessing the first three are the build date, the next the model and material and lastly the ratio.

[Jacfourteen]

Originally Posted by oldblue1968chevy

30 56

30 being the tire spins

56 being d shaft


i came up with 3.73 is this correct? thanks goin into the weeds with the snakes to calcualte the other rearend...

I think I understand what you did, it is the same as prostreetc10 said except you only lifted one tire and you turned the driveshaft enough times to make for round numbers. so if you turned the yoke 56 times and the tire turned 30 times then you divide 56 by 30 which equals 1.867 but the ratio is actually twice that because the spider gears cause the tire to rotate twice as fast as when both tires spin, so you have to multiply 1.867 by 2 which equals 3.734, so I'm pretty sure the rear is a 3.73. Hope this makes sense

[special-K]

I`m not sure,did you spin it that many times?
Did you do what TX Firefighter suggested.It`s downright fool proof.YES,oil will leak out,if there`s oil in there.Get some fresh lube,put a pan under there,and start taking the lowest bolts out all the way.It will start draining.Go ahead and start taking all the others out while it`s draining.If draining is slowed down you can pop the cover off with care.It can take a long time to stop running/dripping.Check the condition of the lube and get back to us.

[oldblue1968chevy]

uhh dang lol i forgot

its been a few hours..but i think 30 is tire spins and 56 is d shaft spins...this is before ANY MATH IS INVOLVED

[prostreetC-10]

You are making it too tough. You just need to mark the tire and spin till the driveline U joint makes one complete circle and at the same time count how many times the tire goes around. You will end with a fraction on the last spin.

[twotrucks]

The numbers represent the number of teeth on the ring gear and the pinion gear.

[oldblue1968chevy]

So do my numbers add up right?

can somebody tell me?

[Aunt-Jemima]

Where did you get your numbers from? The gear or did you spin the tire that much?

[Aunt-Jemima]

And isnt it how many times the drive shaft spins to make one tire rotation?

[prostreetC-10]

Originally Posted by Aunt-Jemima

And isnt it how many times the drive shaft spins to make one tire rotation?

Too many Beers......................YES!!!!!!!!!!

I was bass-acwards!!!!



I can say though that that pinion doesn not have either 30 or 56 teeth!!!!

Are you counting the spider gears??? The pinion you can barely see because the carrier covers it up. If you took the cover off, just look at the last numbers on the ring gear like "big blue" showed us.

[Aunt-Jemima]

haha It happens prostreet

[special-K]

If it`s 3.73 ratio you will spint the wheel 100 times to the driveshaft`s 373 times.Or,if you`re lazy,you could just spin the wheel once and the driveshaft will spin 3.73 times.Or, 3 and 3/4 turns.And if you`re real lazy,I can sell you a tab for whatever ratio you want.
Or,you could read all the suggestions and try those.It`s been well explained,I think,already.

[combustion]

Originally Posted by special-K

If it`s 3.73 ratio you will spint the wheel 100 times to the driveshaft`s 373 times.Or,if you`re lazy,you could just spin the wheel once and the driveshaft will spin 3.73 times.Or, 3 and 3/4 turns.And if you`re real lazy,I can sell you a tab for whatever ratio you want.
Or,you could read all the suggestions and try those.It`s been well explained,I think,already.

haha signature material ^^

[Tx Firefighter]

No, on a 1 legger rearend, you must spin the tire two times. You must double it. For instance, you spin the tire twice, you will find the pinion spins 3.73 turns.

Or, you can buy 2 quarts of lube, a tube of silicone, and a can of crab spray cleaner and do it right. Who knows how old and nasty the fluid in there is. You don't want you bearings running in dirty grease do you ? Do it right. It won't take 15 minutes.

[oldno7]

This is sorta funny. I think you should buy a new ring and pinion and then it will be what you want it to be

[prostreetC-10]

Probably the easiest way to find out what you gear ratio is.....is to pull #3 and #7 spark pull. Take the divided gap of both and times it by your carb CFM. Then you take (in inches) the distance from the front of the INSIDE of your bed and measure back to the full cooler of beer. Now....add up the EMPTY beer cans that are still cold. Take Pie R Squared and times that by the model number on your left front head light. That will usually give you the gear ratio of your rear end down to about +/- .00000000021

[oldno7]

prostreetc-10 You forgot to and the number of lug nuts you have

[oldblue1968chevy]

jacfourteen, i hope you understand, and you others...sorry for my stupidity lol........does anybody else agree with jacfourteen

[prostreetC-10]

Originally Posted by oldblue1968chevy

jacfourteen, i hope you understand, and you others...sorry for my stupidity lol........does anybody else agree with jacfourteen

We just try to have fun on here from time to time.....sometimes it comes off wrong. Some gear heads are super serious. I am not. Didn't want you to think your questions was stupid at all. The chance you take with a forum is that there is no guarantee that you get 100% accurate info. There is no stupid questions though. Sometime we all need to get very simple quesitons answered.

Bottom line is that the "counting the spins" is great if you are looking to buy a truck and want to know if it's a posi and about what the gearing is. If you have already popped the cover, then checking the numbers on the ring gear is the sure thing. The last 2 sets of numbers (4 numbers total) is the pinion teeth and the ring gear teeth. If it says 10 41...the pinion has 10 teeth and the ring gear has 41. 10 into 41 is 4.10 and that is the ratio.