Gear Ratio
 

I was wondering if anyone here would know what my gearing ratio would be for my 1982 C10.

The SPID simply says standard.
The truck originally had a 305 paired with a THM 350 tranny.
The only thing different now is the engine has been swapped for a 350.

If it is any help, I run 2900 rpm @ 80mph.

Re: Gear Ratio
 

If it is any clarification, both tires will spin at the same time under the right conditions, the passenger side tire certainly gets more power in the mud though.

Re: Gear Ratio
 

here's a ratio calculator, http://www.summitracing.com/expertad...tio-calculator need tire size also.

kinda assume you don't want to pull the diff cover and count the teeth? That's the most sure way, teeth of both ring and pinion gear

Re: Gear Ratio
 

Calculator says I have either 1.62 or 1.67 for the diff, pending if i say 2900 or 3000 for 80mph. Running 235 75R15 tires. (seems factory was LR60-15/B on the SPID?)

Which sounds more correct for GM?

SPID is GQ1

Other weird codes are XTS YTS and ZTS all stating LR60/15B TBLS HWY R

Re: Gear Ratio
 

Pull the cover, an easy task, then you know for sure.

Re: Gear Ratio
 

Thats probably a good idea anyway, I can't recall if the grease has ever been changed.

Re: Gear Ratio
 

Im guessing 2:73 gears, I think those were the "standard"

Re: Gear Ratio
 

I plugged the info into the calculator in the link and got 3.13. Close enough to 3.07 to guess that might be what you have. Variations in tire diameter between new and worn, lockup vs non-lockup converter, and how accurate both your speedometer and tachometer are can vary the results.

Re: Gear Ratio
 

Tires are released by front, rear and spare.

X = front tire, code TS
Y = rear tire, code TS
Z= spare, code TS

That way a person could get different tires (like snow tires on the rear) if they so desired.

K

Re: Gear Ratio
 

Limited slip is RPO G80, and is available/listed independently from the ratio.

K

Re: Gear Ratio
 

Need to know the GVW rating.

It's either a 2.56 or a 2.73 depending on GVW.

K

Re: Gear Ratio
 

If you have grease in your rear diff you'll have bigger issues. Should be fluid in there. :lol:

Re: Gear Ratio
 

GVWR is 5600

Now here is the fun part, the engine was a 305 4bbl with ESC, so my diff is 2.73, if Im following that chart correctly.
The diff is limited slip, not indicated by SPID. So I'm guessing GQ1 came with it in 82?

Re: Gear Ratio
 

Nope. GQ1 just means base ratio.

If it is limited slip from the factory it will have G80 on the SPID.

Sounds like it has been messed with. You are not going to know for sure what you have until you take it apart.

K

Re: Gear Ratio
 

That is so odd, no G80 RPO, but I have zero paperwork showing the diff was ever replaced. I have paperwork for the engine and everything else ever done to the Truck.
That being said, papers get lost pretty easy!

Re: Gear Ratio
 

Good Morning,

Might I suggest you find it by counting the revolutions of the wheel vs. driveline method.
It should get you close enough to make an educated find for your ratio.

God bless, Terry

Re: Gear Ratio
 

I think I've seen the G80 on the axle tube around the pumpkin,on mine....
but thats if it was born with one