1980 K10 4x4 with 350 Rear End Need Gear ratio

[mejiar1969]

I’m fixing up a a this truck. The rear end needs to be replaced. There’s no tag in the rear end. Any idea what the gear ratio is hot this truck?

 

[77 K20]

FYI- C10 would be a 2wd
K10 would be a 4wd

Is there any sort of sticker in your glove box? If it is there then it will either say or have a code for it.

3.73s were popular.

Otherwise you can jack up the rear end, put it in neutral and observe the ratio of the driveshaft turning compared to the tires.

Welcome!

 

[Charlie]

 

[Rickf]

Pull the cover and count the teeth.

 

[Goldie Driver]

I will guess 3.42's as that is what is in Goldie , my 80 K1500 Suburban .

That's assuming the same TH350C auto tranny like mine, though .

Good Luck!

Britt

 

[78C10BigTen]

Easiest way to do it is jack it up, pull the cover, rotate wheels till the numbers on the ring gear come to you then find the digits and divide them.

 

[78C10BigTen]

These numbers here. In this case, 43÷14=3.07

You must be registered for see images attach

 

[Arlo]

3.07 Gear

 

[roundhouse]

Could be any thing
I’ve seen 3.07
3.73
4.11
4.56

Only way to know is pull the cover and count the teeth or find the number stamp

You need to change the oil and inspect the diff anyway

 

[HotRodPC]

I've updated the Title to say K10 instead of C10.

You can use this method by jacking it up.
https://www.gmsquarebody.com/threads/how-to-calculate-gear-ratio-wo-removing-covers.3860/

Or you can clean off the axle tube and find the code that's stamped into it and we also have the codes all listed in the Squarebody Library. But that's only accurate if someone didn't do a gear change in past years.

 

[Craig 85]

My California smog '79 K15 had 3.07's.

 

[rpcraft]

3.07 was probably one of the more popular gear ratio's put in the 4wd trucks that came with a TH350. They did put some higher numbers of 3.73's in the 700r4 trucks but 3.07's were still more popular by a wide margin. If you are doing maintenance you should plan on changing the rear diff fluid, so you might as well get you some replacement gear oil and a gasket for each diff, plus some RTV, and have at it. While in there you can spin the diff around, check out the numbers, do the math, and also determine if you have an open diff or whatever going on in there. There's really no way to tell without actually seeing the gears at this point. EVen if you had the RPO code's and other info a previous owner could have changed the gears out.