I had the parts guy today run my serial# to find out my diff. size and gear ratio. He told me I have a 7.625" with 3:42 gears and a G80 Locker I just bought this blazer about a month ago and have plowed with it a few times in low range 4x4 and the rear differential does not act like a posi diff./ locker, I just have the traditional one wheel spin. The blazer has 152 000 km on it and i Know the previous owner and it's been babied all it's life and never been off-road and also know that it is possible that it's the original rear diff. fluid. I'm going to get a new diff. gasket tomorrow and change the rear diff. oil and look inside the differential but what should I look for or inspect while I have the diff. cover off. I will be installing Synthetic 75w90 gear oil. I plow with this vehicle now and need that extra wheel spinning, can anyone please help or have any suggestions Thanks Jody

 

hey, i just did my diff service about 2 weeks ago. go to the diy part of the forum and look at the diff service post by swark. he has pictures and writes what he did. its pretty helpful. i was in the same boat as you. my truck had the same diff oil since it came from factory. i poped it opened and checked the mag. for any metal. i had alittle but that was about it. then look at the gears for ware. after i put everything back together, i went out with friends and was messing around in the parkinglot. wasn't expecting my diff to lock when i hit the gas. i was doin doughnuts. lol, good stuff.

 

It is always possible that it no longer has the same rear end under it...

If it does, it is possible that the governor mechanism inside the diff has broken which is a common problem with the Gov-Loc diffs if abused.

 

When you say the gov lock mechanism is there any pictures on here of what it looks like Thanks I know the vehicles history before i bought it and the rear diff was never touched it was a sunday driver to church and back home unless the G80 wasn't installed from factory it should be there as the serial# says it should will know more in the next few days again is there any pictures please help Thanks

 

Pop the diff cover and have a look. If it looks like the picture below (one of the pictures in the Rear Axle Service DIY post), then it is a G80 and you likely have broken something internal to the diff.