What is my axle ratio?
 

I own a 83 swb and from factory it came with a 250 I6 and a 3-speed with overdrive manual transmission. I am trying to figure out what gears I have in my rear axle. The only information I have is from the Service Parts Indentification card. The option # is GQ1 and the description is Rear Axle - Standard. Can anyone tell me if I can find out the ratio with this information? I am putting a 350 engine with a 700r4 transmission and I want to find out if I can use this rearend or not.

For your 10703 model (short wheel base regular cab, C10) with the MM7 transmission (4 speed manual with overdrive) and LE3 (250-2bbl inline six) the GQ1 ratio corresponds to a 3.08:1 rear axle ratio.

The standard axle ratio with a 305 (350 wasn't available in a 2wd 1/2 ton) and a 700R4 was 2.73 to one, and 3.08 was an available option, so yes, those gears will work fine.

Thanks for the information. Were did you find the information fot all those codes?

I used my 1983 Chevrolet Light Duty Models preliminary data book. It was used by dealers to get the codes to custom order vehicles and see what options were available with what etc... I have a few of them that I bought at swap meets and off Ebay. The RPO codes are also available on the internet, here is a good site.
keep in mind that you needed more than just the RPO codes to figure this one out.

Nice to see another '83 hitting the road again!! 700R4s rock!! I love mine. My 305 can beat them 255/60R15 tires with the 3.08 pretty good.

My 250 /w 3 speed manual has 3.73's as the "standard axle"

but thats in '80 not 83

Well, according to my 79 dealer sales album (I don't have any literature for 1980, KIILEW where are you?) 3.73 gears would only be available with a LE3 250 I6 with an MM3 3 speed standard trans in a half ton if it had the F44 (Big 10) heavy duty rear suspension. Even then, the GQ1 standard ratio was 3.07 and 3.73s were optional with code GT4.

This all depends on engine, trans, and GVW of the truck. Saying 1/2 or 3/4 ton isn't even close enough since there were various GVWs even between those.

I still can't figure out my axle ratio. I pulled the differential cover off to try to find out for sure what ratio I have. I found a set of numbers on the largest gears. 1 GM 1235124 15 41 3 83. I have heard that if you divide the middle numbers it will tell you the ratio. 41/15 equals 2.73. Is this my ratio?

Yep.