Rear end ratio?

[87Bob]

I have an 85 LB 1/2 ton 305/350 does any one know what the stock rear end gear was? The build sticker in the glove box says standard rear end. I had heard that if you jack one rear wheel up and turn the drive shaft by hand counting how many revs it takes to make the wheel turn one time you can use that as a ratio. Can anyone confirm that?

[3r!c84]

2.73 is stock.but you would have to open the cover and count the teath

[menace121978]

yes counting the teeth would be more exact but you can raise it up and i think both tires have to be in the air... 1st mark the drive shaft somehow and spin the wheel a full turn while counting how many times the drive shaft goes around. some say to do it in 3 spins and divide by 3 but i dont think its necessary.

say the driveshaft goes around 2 3/4 times you have a 2.73. goes around a touch over 3 you have 3.07. etc...

[TurnNBurn]

a standard rear is 3.07. seen them many times

[glock35ipsc]

My SPID says something like "standard rear axle, 2.76 ratio".

[TwoFiftyShifter]

My spid says sometihng like

code 05969490ejq11b

I don't remember it being easy to follow.

[Desert1957]

Originally Posted by TurnNBurn

a standard rear is 3.07. seen them many times

It was NOT the standard rear ratio........

2.73

[LiveAnimals]

huh I always thought they were 3.08s, learn something new everyday

[2tons of fun]

not realy seeing as how not every truck was built the same and 2.73, 3.08, 3.42, and 3.73 are all perfecty possible gears in any matching truck.

[shrtbx]

very true...not every truck is built the same. The owner that had mine left a little thing in the glove box that looks like a credit card. It has all the options that he bought for it on the card. You can never tell with chevys from my experience. The first vette that i owned had all kinds of non typical options on it.

[dbmx66]

Originally Posted by shrtbx

very true...not every truck is built the same. The owner that had mine left a little thing in the glove box that looks like a credit card. It has all the options that he bought for it on the card. You can never tell with chevys from my experience. The first vette that i owned had all kinds of non typical options on it.

yea i have one of those too

[86k10]

look next to where it says rear axle standard there should be an axle code.

[TeamRinaldi]

mine's an 85' SB that was originally 305/350, now 350/350. Stock 2.73's.

[kenm78]

My sticker in the glove box for my 1980 says 3.07

[asphaltburner]

Yo! My axles have a code stamped into the back of the axle tube that can provide the factory ratio, but that guarantees nothing. I like the idea of counting revolutions of the driveshaft,...that at least gives you info on what's actually installed.
Todd.

[lakeroadster]

Originally Posted by menace121978

yes counting the teeth would be more exact but you can raise it up and i think both tires have to be in the air... 1st mark the drive shaft somehow and spin the wheel a full turn while counting how many times the drive shaft goes around. some say to do it in 3 spins and divide by 3 but i dont think its necessary.

say the driveshaft goes around 2 3/4 times you have a 2.73. goes around a touch over 3 you have 3.07. etc...

To check rear end ratio jack up one tire if you have an open diff, or both tires if you have a working posi or locking differential. Rotate the tire one full revolution for posis and lockers and 2 full revolutions for open diffs. Carefully count the number of full revolutions the driveshaft makes. This is your gear ratio. In other words, if the drive shaft turns 3 ¾ turns, you probably have a 3.73 gear ratio. Turning the tire for twice the number of full revolutions and dividing the drive shaft revolutions by two will give you a more accurate reading.