1986 c10 locking differential not locking
 

Hey guys i have a 1986 chevy c10 with a 350 crate motor makeing around 325hp and everytime i spin a tire its always spun the right tire so i thought it was just a peg leg diff but the other day i was looking at the original build sheet and it says that it came with a 2.73 locking rear differential
this truck was my grandfathers so i know that the differential is original the only things done to the truck is the wornout 305 was replaced with a brand new goodwrench 350
any tips on fixing this without spending all of my money

The diff you have is called a gov lock diff. It acts like an open until it builds cintrifical force and locks the diff. Not a good idea to do burn outs with this diff. See video

^ That video does not exist????

Probably because I was using my iPhone. I will try and load the vid again from my PC later

is it a good diff or should a try to find a better one at a junkyard or craigslist

It's a great diff if your stuck in the mud, as far as street performance not so ideal. If you want something that will hook up and not one wheel peel I would look for a true posi unit with clutches and springs. Unfortunately a decent locker is going to run you 300-700 bucks. Yes sometimes you can find used on eBay or Craigslist but most of the time they need rebuilt with new clutches and springs.
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Lets try this again!

you want an aftermarket one those are not good for much. you dont want to get used stuff either because it will be just as beat as what you have

The G80 Locking rear differntial will work engage when one wheels spins faster then 100 rpm and will disengage at about 20 mpg. The G80 locker is designed for OFF-ROAD use and not a performance axle. Limited Slip Differentials (Posi) are designed for that purpose.

Also, never never install a limited slip additive in a G80 locker or it will result in not allowing the locking mechanism to function properly.

Note - The G80 Locker and the G80 Limited slip (yes same option used for both) require routine maintenance. In other words the fluids needs to be changed, contaminated or work out gear lube may cause it to not function properly.