Comments on: 1986 Chevy K10 truck stock rear end gear ratio?

By: Chad H

Chad H — Mon, 13 Jul 2009 10:18:48 +0000

I have an ‘84 K-10 with a 4-speed and my truck has a label on the drivers side wheel well under the hood. This label has the VIN number along with all the other build information about your truck. It will have your gear ratio in this information.

I’m willing to bet that it is a 3.08:1. That was the standard gear ratio. There are other ratios that are optional such as 3.42, and 3.73. Although I do have a buddy that has an ‘85 GMC with a 4-speed and he clames that he has a 2.73:1.

By: boogie_4wheel

boogie_4wheel — Sat, 11 Jul 2009 04:52:00 +0000

Look inside the glove box for a sticker listing the RPO build codes. These codes list all of the options that the truck has (color, engine, tranny, axle ratio, special package, ect).

If you cannot read the sticker because of damage or missing; you can simply jack up the rear of the vehicle (both tires). As said above, mark tires and driveshaft, and turn driveshaft (counting revolutions) to turn both rear tires one full revolution. And as said above ~3.75 turns on driveshaft would equal a 3.73 ratio, slightly over 4 turns of driveshaft = 4.10 ratio, ect.

Another thing to do is to remove the rear differential cover. The ring and pinion tooth count is stamped in to the ring gear, simply rotate the rear tires to find the stamping, then divide the two numbers to get the ratio. This would be a good idea because you can also inspect the gears for wear and replacement, as well as you can replace the axle lube.

By: juttin

juttin — Thu, 09 Jul 2009 09:33:14 +0000

it is probably a 3:73, if you get much larger tires you want to get a 4:10 ratio.

By: Scott

Scott — Tue, 07 Jul 2009 12:29:32 +0000

The 1986 K10 with the SM465 4-speed manual, which is what you have, came with a 3.73 ratio.

By: blownhemicharger

blownhemicharger — Mon, 06 Jul 2009 17:57:12 +0000

there may be a tag located on the diff cover but often they are missing, you can jack the rear wheels up and put the truck in netural (block the front tires) then put a mark on the tire and rotate the driveshaft by hand counting how many turns it takes of the driveshaft to make the tires turn once around. This will give you a pretty good idea on the ratio (3 1/2 turns 3.55 gears, 3 3/4 turns 3.73 gears). Or pull the diff cover and look on the ring gear it wll be stamped on the outside. you also may be able to call the dealer and give them the VIN number and they may be able to look it up.