4x4jimbo

i have wat i was told is front and rear 81 chevy blazer axles on a project of mine . i need to find out the ratio. my rear end is apart and out of the vehicle . if i need specific numbers from any parts to help please just ask...my next option is just replacing them both but i only need the rear replaced if i can figure the ratio. its 10 bolt 6 lug

thanks jim

therewolf

Hi 4x4jimbo,

Welcome to the Chevy Forums.

Do you have either the VIN or a copy(inside glovebox) of the RPO codes for that Blazer?

In any event, bearing in mind the axles are 30years old even if they were still in the original body, and a gear swap could have been done by any prior owner, it might just be best to change both gears to be certain.

4x4jimbo

well theres realy no way of looking in the blazer lol. its a 85 dodge van with chevy axles .well i did find a front and rear end with good guts .i just cant change the axle houseing itself becouse there well costumized to fit the van.i heard a trick of spining the wheel and depending on how many times the driveshaft spins , you divide that number with another and you get your ratio is this trick true??

thanks jim

therewolf

Yeah, technically this works, but IMO it's a poor way do determine exact ratios.

Say for instance, you're counting the turns, and the driveshaft mark rotates out of sight at the end of the wheel rotation. How are you going to actually KNOW the difference between, say, 342's and 373's, or 410s and 456s?

The best insurance, because you can't really be sure the gears weren't swapped out prior to this, is to procure new gears for both differentials. A new set of bearings would probably in order for both, too, considering the age of the units.There are a couple advantages to doing this, first you know authoritatively which gear ratio is being used. Second, you get to hand-pick the proper gear ratio for your personal driving habits and need.

You can try mortec.com, and carnut.com for any OEM info you can find on the differential casings(who told you the differentials came from a Chevy? ) but you're still taking a chance that someone hasn't changed the OEM gears since they left the factory.

BTW, I loved my Dodge Van. Lots of room, a steady ride,and decent gas mileage. It was only a half-ton with V6 and 2WD, but it ran great.

frickenbored

open the cover and there will be numbers stamped on the ring gear. The numbers will be the teeth on the ring gear and the teeth on the pinion. divide the bigger number by the smaller number. for instance if you have 41 teeth on the ring gear and 10 teeth on the pinion your ratio is 4.10:1. I wanna say that all 10 bolt ring gears have 41 teeth and its the pinions that differ.