14FF questions, including G80. swaps and functions?

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wb292

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The G80 does not use clutches. It's a binding gear type. The small drum spins when one wheel turns faster than the other. This turns a gear on a spider causing it to bind the spiders up and somewhat locks the axles together. A weight mounted next to the drum slings out above 20 MPH releasing the gear and opening up the spiders for normal open diff operation. You can and I have removed material from this weight so It releases at higher speeds. It does not matter what oil you use as long as you use the correct weight. Back to the OP. The carrier split is at 4.56.
So you can use the same carrier for 3.42, 3.73, and 4.11. Yes they made a 3.42 gear set in the 80's for the 10.5 FF. My 1982 K2500 GMC has them with the G80 carrier.
 

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The G80 does not use clutches. It's a binding gear type.
"Binding gear type"? Are you thinking of the helical-gear Torsen and the competing Eaton TrueTrac?

As said...the G80 "Gov Locks" in all flavors use clutches, and GM says to not add friction modifier to the gear lube. What they DON'T cover very well is whether friction modifier already blended into the gear lube is acceptable. The bulletin calls out a specific part-number for GM gear lube, and that number has been superceded at least once, and maybe more than that.

As best I can tell, the correct fluid is the very expensive "grape juice" scented stuff. But I've never been able to trace the superceded part numbers to be sure.

When I installed Amsoil Severe Gear (with factory-blended-in friction modifier), the G80 in my 9.5" semi-float quit working. Took two changes of fluid to the Valvoline pictured in my previous post to get it to work again...and I'm still not sure it's working 100%.

The clutches in a "limited slip" differential are intended to slip. They're preloaded with springs to vary how much torque it takes to cause slippage, but slip they do. The clutches in the G80 Gov-Lock are not intended to slip. They're like the wet clutches in an automatic transmission--they have limited slippage as they engage and disengage, but when fully engaged slippage means death. They're intended to operate "locked".

The clutches in the 14-bolt Full Float are different from the other Gov-Locks in that they seem to be prone to grabbing/chatter. GM says some amount of that is "normal".

Animation of operation:
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