since the cold weather has set in here in wisconsin, i noticed that when i am on some ice with one drive tire and the other tire is on dry pavement and get it some gas, my diff acts like a standard open diff. i know that my blazer has a g80 locker in it from factory, ive had it engaged many times before. i did replace the diff oil about a month ago, so i crawled under the blazer and dipped my finger in the fill hole and the oil is nice and clean. i hope i didnt blow out my g80, but now it seems really hard to get both tires to spin unless i am on gravel or something that is loose. i can just about get the diff to lock in if i stand on the brakes hard while on ice, but even then the g80 doesnt want to lock...am i doing something wrong or is she a goner?

 

How fast where you going?

 

i was at a stand still. stopped on some ice and gave her some gas and she just did a one wheel peel on the ice, it seemed like it wanted to transfer power the tire on the dry pavement but just couldnt lock in even while having the wheel spinning slow all the way up to about 20 mph on the speedo. i used a synthetic 75-90 oil, would this effect the clutch packs in the g80?

 

The oil shouldn't be a problem. I used Mobil 1 75w90 in my Bravada with no adverse affects.

Sounds like something isn't right in the diff.

 

i just dont understand how it can go from working to not working at all, just makes no sense. i just would hate to take it all apart again to look at the diff to see if something broke, at 10 bucks a qt and being in college, that 20 bucks is needed else where ya know

 

You could siphon it out maybe. Or really really clean the outer housing and save the oil? Can you not jack up the **** end and turn one wheel and have a friend nearby to stop the other wheel and see if it locks up?

 

yea i could jack up one tire and leave the other tire on the ground but i dont think i can get the tire to move fast enough by hand...100rpm is a lot by hand isnt it?

 

100RPM is quite a bit to spin by hand... You could try spinning one tire with the other off the ground and the transmission in park, but this would cause the wheels to spin opposite each other and momentum may cause a problem when it locks. This would require you to spin the tire only 1/2 of what it would require for lockup. Since the other wheel will be spinning the same speed in reverse, the difference in RPM will work out right. Like I said though, I do not know if this will cause any issues with the diff. It is definitely not something you want to do a lot of.

I just did it on my Rainier and to reduce the momentum, I removed the opposite wheel on the rear axle and spun the other one. Locked up with minimal effort and stopped it dead.

 

that sounds like a good idea, i will take my truck up to our shop (my in-laws own a towing company so i get to use their shop) and try that after i take it apart and see what is going on since i have to do an oil change on the engine anyways, i may snap a few pictures and show you if something is broke. also, the auto parts store was out of synthetic gear lube, so i got just the plain old 80-140 (i like a little heavyer oil for extra protection) that is rated at the GPL-5 or whatever the rating is, would that be ok to go back to normal oil? i wouldnt think it would hurt it

 

g80 is not a locker. it is a locking differential. this is totaly different in all aspects of the mechanics involved. like you were advised to do, you have to get one tire spinning faster than the other for it to engage the differential as 'locked'.

There are weights that activate and deactivate via centrifugal force that allow the diff to float from locked to open and back. it will work at low speed as if it were locked (like a solid axle) and will disengage as you get more RPMs at the wheels (more like turns per minute). After you're at any speed in which the axle has gone 'open' on you, the only time it will "lock" again is if one wheel spins more than 100 rpm fast than the other. This is actually pretty bad because it puts a lot of strain on the parts in there. think of it this way, if you wedge a pencil in to a fan it doesn't just "stop" the fan. the blades bounce and chip against the pencil as they are spinning faster than the pencil is moving into the blades.

That being said, unless you actually pick up the vehicle and spin the wheels to "manually engage" the diff, you will not be able to tell by just putting one tire on the road and one on some gravel and punching the gas. i dont care what car you're in, the wheel on the gravel will have less initial traction than the pavement side, lockers or no.

don't give up on the g80 just yet. you can take the diff cover off and inspect the parts inside. has some stuff that will show you what a good, fully assembled g80 looks like, and a g80 with broken teeth, weighted triggers, bent gears, etc.

You're in a '98 with less than 45k miles on it. I'm going to guess that your rear end is fine, but it doesn't hurt to check it out. Read up on it. It's actually a very interesting design, and if you look into it more, maybe you will get a better feeling about hhow it is supposed to work and it's limitations.


Or, dump the money you would rebuilding/replacing the one you have on a Power Trax No-Slip Locker and pray it doesn't rain