I have a 1989 GMC Sierra (not xc) that needs a new odometer. The mechanic said he needs the rear end size (NOT rear track) - it's in a "ratio" format. We called GMC dealers, but no one can find info dating back to 1989 models. I searched online everywhere. Can anyone help me? Thanks!

you might have to do it the old fassioned way by jacking up either one wheel or 2(posi) and turning the driveshaft by hand untill the wheel makes 1 revolution. if you jack up one wheel turn the driveshaft untill the tires makes 2 revolutions(differential action) the number of turns the driveshaft makes is your ratio. my 89 has 3.73's i think 3.08's are common on 2wd

I have a 1989 GMC Sierra (not xc) that needs a new odometer. The mechanic said he needs the rear end size (NOT rear track) - it's in a "ratio" format. We called GMC dealers, but no one can find info dating back to 1989 models. I searched online everywhere. Can anyone help me? Thanks!



You can check by your vin #, I think your able to indentify by one of the last seven numbers

Your axle code should be on a sticker on your drivers door or pillar.

From that code, they can look it up.

There is no way to tell you without either the code, vin, or simply counting the revolutions because several differential ratios were available.

Jim