What gear do I have?

[4thgentruck]

Was wanting to know what gear choices would have come in my truck from factory.

Its a 77 c10 shortbed that origionally came with a 6 cylindar. Not sure what trans im assuming it was the 350 turbo. I have the gm 12 bolt.

Can anyone give me what options come in it.

 

[Tyger13us]

Was wanting to know what gear choices would have come in my truck from factory.

Its a 77 c10 shortbed that origionally came with a 6 cylindar. Not sure what trans im assuming it was the 350 turbo. I have the gm 12 bolt.

Can anyone give me what options come in it.

i have 2 77's with 6's in um with 12 bolts and there both 3.72.3333333's....

the only way to know for sure is pull the cover,, count the ring gear tooth count and then count the pinion tooth count,, but on alot of gm gear sets its stamped on the ring gear and sometimes the pinion also,, then devide them and it will give the ratio.....

 

[J Knight]

Last night I pulled the cover off my 12 bolt that came out of a 74 6cyl 3spd. Its a 3.07 open diff. 14:43

 

[RetroC10Sport]

3.40 std, 3.73 opt. Unless it's a Big 10, then 4.11 was optional as well as the other two.

 

[Tyger13us]

Last night I pulled the cover off my 12 bolt that came out of a 74 6cyl 3spd. Its a 3.07 open diff. 14:43

wish i could find one of those,, everything i have 12 bolt is 3.72,, even the 10 bolts,, but i do live in farm land,, so i guess thats what every one wanted.......

 

[HotRodPC]

wish i could find one of those,, everything i have 12 bolt is 3.72,, even the 10 bolts,, but i do live in farm land,, so i guess thats what every one wanted.......

Those 3.07/3.08's are dime a dozen in the 80's models trucks. My K1500 is the first half ton I got with 3.73's. The rest of the 1/2 tons in the 80's were 3.08's and 1 2.73. All were auto trans too and that might make a difference.

 

[4thgentruck]

I was hoping it was the 4.11 ill have to pull the cover, and see if its stamped. If not when i count the teeth how do i determin the ratio

 

[crazy4offroad]

Divide the small number into the big number.

 

[4thgentruck]

Ok cool ty. Dont know why but i was thinking I had a 4.11. But ill pull the cover and count them or see if its stamped on the gear.

 

[HotRodPC]

It's not really necessary to remove the cover if you have a jack. First thread in the Diff and Driveline Category is: How to calculate gear ratio without removing the cover.

http://www.gmsquarebody.com/forum/showthread.php?t=3860

 

[4thgentruck]

Darn I forgot about that thread. Thanks HotRod

 

[4thgentruck]

Ok I did what the instructions said and when i had it jacked up and spun one wheel the other did nothing. Then went and spun the other wheel and it too spun the yolk but not the other wheel. Whats that mean?

And I got alil less than 1.75 turns out the yolk. That means I have 3.42 gears correct?

 

[HotRodPC]

Pretty much just mean you have a peg legger open differential. If that's the case, I'd do it with only 1 wheel up so the other stays stationary to get get an accurate count on the yoke.

If indeed it is 1.75 turns and obviously an open diff, then yep, 3.42.

 

[4thgentruck]

I jacked it up to check if it had a locker or not then put one wheel on the ground like directed. And that aught to get better gas mileage. But with a 383 thats kinda out the window anyways lol.

Should I go ahead and but a 3.73 or something to know its new and not 36 yrs old?

What would you do?

 

[HotRodPC]

If you're still running a Non Overdrive trans, 3.42 is good ratio for a half ton IMO. And no, for a 1/4 turn to go from 3.42 to 3.73, I wouldn't spend the money. I'd keep the 3.42's. If had an OD trans then I'd go 4.10/4.11.