Differential Fluid advice

[Zoomalot]

"LSD" = CHATTER, CHATTER,CHATTER without Additive.
G.M. still sells the little bottles and in my opinion is the best additive for CHATTER which is another name for
clutch WEAR.

 

[hatzie]

"LSD" = CHATTER, CHATTER,CHATTER without Additive.
G.M. still sells the little bottles and in my opinion is the best additive for CHATTER which is another name for
clutch WEAR.

Agreed.
However... It would be exceptionally unusual to see a LSD in these trucks.
We're talking about 1973-1991 squarebody pickups based on a late 1960's design. GM didn't factory install a limited slip in light trucks til at least the second generation past our trucks... at least 1998 T800 and probably 2007 or later T900 models.

If you're trying to equate the stock G80 Eaton Gov Lock with a Limited slip... stop... and back up that train of thought.
Locker does not equal Limited Slip. They are very different animals. Using limited slip additive in the stock G80 Eaton Gov Lock will make it chatter and fail.
If your aftermarket locker calls for Limited Slip Additive then use it... It's a complete waste of money to use it in an open diff and bad mojo in the G80.

Make darn sure the previous owner, or you, installed an aftermarket LSD in place of your trucks' original diff(s) before you pour in that little bottle of additive.

 

[Frankenchevy]

didn't they install a trac-loc(?) or something by a similar name in the d60 of some m1028s? I believe that's a form of an lsd, but I'm not positive. just playing the devil's advocate, but it stands to reason that someone could have factory ordered one as well, if gm were offering it.

 

[hatzie]

If they were offering it.
The D-Series CUCV were special order government machines.

I don't believe the CUCV came from GM in the M1029 & M1031 configuration.
I read once that both of those were M1008 CUCV trucks modified with DOD approved kits to carry various flavors of utility boxes.

Trac Loc is a Dana Spicer offering and there are rumors of them on the M1028 & M1031 with the Dana 60 front and Dana 70 dually rear. Not sure if it was the front or rear that got the Trac Loc LSD. Given the aversion GM engineering seemed to have for LSD in the front and trucks, in general, I'd say it was in the rear but no guarantees. Perhaps @Keith Seymore may have some idea about this as he was working for GM at the time... If GM was even involved in the conversions.