rear end curiosity

[68lngbed350]

Im a little confused, my 68 3/4 ton chevy has a 10 bolt rear end. I was told 3/4 tons never came with 10 bolts, only 12 bolts. Is it possible somewhere along the line that someone replaced the original 12 with a 10 bolt. The trucks been in my fam for over 20 years but before that i know it had a handful of owners. Any helpful input would be appreciated.

[Shaky]

Does it look like the one below? That's not a "10-bolt" per se. It has a 10 bolt cover, but is commonly called an "Eaton" and is a different class of differential. To my knowledge 10-bolts were not used in 67-72 trucks.

[Blazer1970]

Also, no 12 bolt ever came in a 3/4 ton. The 12 bolt is a half ton axle.

[martindc1]

Don't dana 60s have 10 bolts on the cover?

Is your axle a full floater with 8 lug wheels?

[GASoline71]

It's actually not the number of bolts that hold the rear cover on that are counted. It's the number of bolts that hold the ring gear on the carrier. It just happens to coincide with the number of rear cover fasteners.

There are some B.O.P. rear ends that have 12 bolts holding the ring to the carrier, and 10 bolts holding the diff cover on.

...and I'm betting that the truck in question has the Eaton in it.

Gary

[Longhorn Man]

you guys are confusing the term 10 bolt.
The 10 bolt rear is not just any rear with 10 bolts holding the cover on. It is a specific design of rear end that GM used.
The 3/4 tons of this era mostly had the corperate rear, or as we call them on here, the eaton. There were plenty of 3/4 tons 67 - 72 with the dana rear too.

[68lngbed350]

shaky: yes my rear end is identical to that one pictured.
martindc1: i dont know if its a ff but its definitely an 8 lug
thanks for all the replies fellas. since it seems i have an eaton rear, does anyone know what gear ratio it has?

[vectorit]

No way to tell by just looking at it, just a lot of speculation.

Though being an "Eaton" the gear ratio choices are slim.

So, my shot in the dark is it may have a 4.57 gear ratio.

check all the bolts holding the cover on, and see of there is a little metal tag.
If there is, then it will tell the gear ratio.

[68lngbed350]

no metal tag, but i have heard that a metal tag on the rear end means its posi. Is this true?

[martindc1]

If its identical to the one pictured it is a full floater, meaning that you can take out the axle shaft without taking the wheel off. As far as gear ratio, I'm guessing probably 4.57 or possibly 4.11.

[Longhorn Man]

what engine and tranny were in it originally?
4.57 and 4.10 were the 2 common ones in single rear wheel trucks.

[68lngbed350]

tranny wise it still has the stock sm465, the original engine was a 327.

[srr]

Jack up one wheel. Rotate it through two revolutions. Count how many times the driveshaft rotates= ratio.

[68lngbed350]

thanks alot ssr. I had tried this in the past but I would only rotate the tire once. Leaving me scratching my head. The driveshaft spun 4 and a half times. 4.57's it is.