I have pulled out two rear ends both from 1991 k5 blazers i was trying to swap the one that has a Detroit locker with my other one problem is neither have the tags telling me the ratio so i dont know if there the same is there anyway i can tell without pulling the differential apart? and if there isnt how do i go about getting it after i took the Cover of the differential off?

 

i'm not sure about the k5s, but on the newer blazers there is a sticker with some numbers and letters on it. each grouping of numbers and letters means some option that is on that vehicle. one of which will tell you the gear ratio and if you have an open, posi, or locking rear end.

 

You have to pull the cover off. On the side of the ring gear you will find a set of numbers that look like 41 11 that tells you the number of teeth on the ring gear and the number on the pinion gear just divide those two to get your ratio. If you can't find those numbers then just count away. Going by the tags is always risky cause you never know if someone changed the gears

 

i noticed the numbers engraved in the ring gear after i counted the ring and pinion i got 40 and 13 so that works out to 3.0769230...... does this seem to be right??? thats just the one i havent touched the other one yet cuz i was doing on the rear that im just getting rid of first to make sure i was doing it correctly

 

Yep, that would be 3.08 gears. The numbers don't always turn out to be exactly on the average.

 

awesome thank you all for your help

 

so as i was saying yesterday i counted the ring and pinion on my one blazer getting 40:13=3.08
so today i pulled my rear form my other blazer to count the ring and pinion on the (this one has a posi locker in it) i got 41:12=3.42

now i wanted to put the posi rear end into my other truck since the gear ratio are not the same i need to change the front differential to be 3.42 as well???? or what?

 

Yes, if you change the gear ratio in the rear you must also change the front to match.
If you had different gear ratios front and rear and put the truck into 4WD it would be like throwing on the parking brake!

 

yeah thats what i figured.... so in ur opinion do you think it would be easier for me to buy new gears for the front and do it my self... or to just put the truck together with the posi rear end in it take it to a shop in 2wd and have them change the front differential.. or pull the front pumpkin out and swap that with the one on my other truck (which idk if thats possible) but im not so much worried about money im more worried about getting the truck done before winter

also if i did replace it with a new one by my self i would just have to buy new ring and pinion gears or would there be other stuff i would have to get too??

i forgot to add the truck im putting this is i have to take the whole suspension out for my new lift kit too so i would be dropping the front end off the leaf springs and all that good stuff anyway so i was thinking it would probably just be easier to swap front axles too?? NO?