It might be a good idea to test it so that you can find out if it needs service before you really need it.

 

That is what I did by using 4wd on that trail for a good 45 min.

Worked fine, no problems.

 

The older ones the transfer case encoder motor sometimes starts to act up before they fail.
All once in a while I do switch to 4HI to check...

...Every third or fourth time or so on a suitable road or track 4LO to figure if all switches as it should.
There is still the transfer case that needs to switch and the front axle as well.

For the rear locking differential I would prefer a fixed ratio (silicone) or Torsen but the G80 in my Blazer does the job. It just needs one rear wheel spinning faster than the other to lock but then locks at 100%. A Torsen would be nice but is very expensive.

As the G80 is or was a OEM option inserting one should be pretty easy.

 

So since it shows that they is friction discs in there, should friction modifier fluid be added if you change gear oil?

 

The G80 diff does not require friction modifiers in the gear oil. This is in part due to the engagement/disengagement design of the clutch packs. Unlike clutch type positraction differentials where spring pressure is always putting a fairly high amount of pressure on the clutches and steels, the G80 only puts pressure on the clutches when it senses a speed difference between the output shafts at which point it will lock up (provided everything is working properly).

 

Thought I would update this thread: I found a used locker. Have not determined when I will be installing yet, but will probably be after temps are in 100's.....
I just bought the carrier, will re-use my ring gear and of course the pinion gear, just have to get the lash set correctly.
Just got the diff gasket today, still need to get more gear lube.

Will I need to add friction modifier to the gear oil?

 

No on the friction modifier

 

Ditto to what NewGuy said: No friction modifier according to my owners manual. It calls for "GM Part No. 1052271 or equivalent" for the differential, even for the G80s.

 

Ok got it...no modifier. Had I just "read" the post above mine I would have known before asking.
Thanks for the responses.
The guy that sold me the locker gave me the set of shims that came with it, so hopefully I am ready to install; just got to pick a day to do so.....going to be right at 100 this weekend, oh boy!

 

I've found my Blazer does alright.

I'd much rather have my Jeep for poor weather conditions. Off road wise, I am sure my Jeep would still flex better and be more capable, but it's slightly lifted too.

My Blazer needs a G80'd rear though.