What Gear Ratio? 82 K10

[Splandman]

I have a 1982 K10 with a 350 and a 700r4. I am going to put a motor in soon and need to know what gear ratio I am running. Is there any way to know what gear ratio I am running other than looking at the actual gears.

 

[chengny]

If it is the original axle, you can just check the RPO sticker in the glove box:

GH2 76 87 AXLE,RR 2.29 RATIO
GH3 86 88 AXLE,RR 2.77 RATIO
GH4 76 81 AXLE,RR 2.28 RATIO
GM1 87 87 AXLE,RR 2.59 RATIO
GM3 85 88 AXLE,RR 3.45 RATIO
GM7 82 83 AXLE.RR 2.39 RATIO
GM8 76 88 AXLE,RR 2.56 RATIO
GS4 85 86 AXLE,RR 3.70 RATIO
GT4 76 88 AXLE,RR 3.73 RATIO
GT5 76 88 AXLE,RR 4.10 RATIO
GT8 76 88 AXLE,H.D. RR 4.10 RATIO
GU1 76 87 AXLE,RR 2.41 RATIO
GU2 76 88 AXLE,RR 2.73 RATIO
GU3 82 85 AXLE.AR 2.93 RATIO
GU4 76 88 AXLE,RR 3.08 RATIO
GU5 76 88 AXLE,RR 3.23 RATIO
GU6 76 88 AXLE,RR 3.42 RATIO
GV4 82 87 AXLE,RR 3.36 RATIO
GV8 82 85 AXLE,RR 2.72 RATIO
GW4 84 85 AXLE,RR 3.31 RATIO
GW6 85 88 AXLE,RR 3.27 RATIO
GW9 76 88 AXLE,RR 2.93 RATIO
GX3 82 88 AXLE,FRT 3.33 RATIO
GX4 76 83 AXLE,RR 3.75 RATIO
GX5 76 83 AXLE,RR 4.09 RATIO
GY5 76 87 AXLE,FRT 3.65 RATIO
G44 85 87 AXLE,RR 3.07 RATIO
HA3 82 88 AXLE,RR 5.29 RATIO
HC2 76 81 AXLE,RR 2.76 RATIO
HC4 76 88 AXLE,RR 4.56 RATIO
HC7 76 88 AXLE,RR 5.13 RATIO
HC8 76 87 AXLE,RR 3.21 RATIO
HD1 82 84 AXLE,RR 5.83 RATIO
HE3 76 84 AXLE,RR 3.07 RATIO
HE4 76 81 AXLE,RR 3.40 RATIO
HF7 76 88 AXLE,H.D. RR 4.56 RATIO
HF8 76 88 AXLE,RR 4.88 RATIO
HK1 82 86 AXLE,RR 2.87 RATIO
HK9 82 84 AXLE,RR 5.86 RATIO
H04 76 87 AXLE,RR 4.11 RATIO
H22 76 81 AXLE,RR 6.17 RATIO
H23 76 81 AXLE,RR 5.43 RATIO

 

[Splandman]

My sticker is missing from the glove box. I do believe it has the stock axle though. Mechanically, pretty much everything on the truck appeared stock when I bought it. It had been painted and the interior has been redone but everything else seemed stock.
I am also missing the sticker on the inside of the door frame.

I can't believe there were that many different rear end gear options.

 

[nvrenuf]

Pull a diff cover, the tooth counts are stamped in the ring gear or count the teeth on each gear.

 

[chengny]

Someone smarter than me writes:

Jacking one wheel up and turning the engine over by hand will let you determine the ratio. Make a chalk mark on the bottom of the tire and crank the engine over exactly 2 revolutions. Also, make sure all the slack is out of the system when turning the engine over. Then measure the rotation on the tire. It will be plus or minus one turn, but accuracy with these measurements is critical. Take this tire rotation value, divide it into 1 (in other words, find its reciprocal), then multiply it by 4. This will give you a pretty good ball park of the ratio, which can be compared with known ratios (4.11, 3.78, 3.54) to see which one comes closest. For example, I recently went through this with my car and found the tire rotated slightly less than one turn for 2 engine turns, so I used a tire rotation value of 0.95. Dividing this value into 1.0 gives you 1.05, and multiplying 1.05 by 4 gives you 4.20. So I figured the rear end ratio was 4.11. I then used this method on a friend's car before he pulled the rear end out. I got about 1.05 tire rotations for 2 engine rotations, which figures out to a rear end ratio of 3.8. When the gears came out, sure enough, they were 3.78.

1) Jack up one rear wheel and chalk-mark the 12 o'clock position on the tire. (Make sure the slack is out of the drive train)
2) Hand crank engine 2 complete turns.
3) See where chalk mark on tire ends up.
A) Between 11 and 12 o'clock, ratio is 4.11
B) Between 12 and 1 o'clock, ratio is 3.78
C) Between 1 and 2 o'clock, ratio is 4.54