dnewton3
Staff member
The "G-80" GM RPO code has been used, unfortunately, for many different differentials in many different applications over the decades.
Because the OP is referring to his mid-2000s GM truck, the G-80 RPO option induced the "Gov-Lock" for use (aka the Eaton M-locker; as shown above). I know of what I speak; I had a 2006 3500HD for a decade and serviced the diffs a couple of times. That "Gov-Lock" was not-so-affectionately known as the "Gov-Bomb" because they had a propensity to grenade themselves under severe off-road use; the "locking" function was so fast and harsh they often just exploded the internal goods when used hard. On-road, they last a fair bit longer. In theory, they should be a good unit. In reality, they were a bit of a risk.
In a simplistic description, these Gov-Lock (M-Lock) units are a limited-slip clutch system when in "normal" mode; the clutches are always slipping to allow the differential to have a low bias for normal daily driving. Then when high-bias is needed, the flyweight locks immediately upon a 100rpm delta (as seen in the video), and those cam-ramps slam the clutch pack tight, causing a shock to the internals and the axle. Oddly enough, though it's called a "locker", it's still just a clutch pack and enough driveline torque can still overcome the clutches, so it ends up slipping anyway, (or shattering components internally).
When new(er), the Gov-lock can provide some fairly high bias in "lock" mode. But as the clutches wear, the have almost no bias in the normal mode and not much more in the "lock" mode (essentially, they don't "lock" nearly as tight as they did when new). This is all because, at its core, it is in fact a limited slip unit and not a true "locker". (not like an air-locker or Detroit locker).
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OP; yes the Mobil 1 gear oil has some L/S friction modifier additives and would be fine to use.
Because the OP is referring to his mid-2000s GM truck, the G-80 RPO option induced the "Gov-Lock" for use (aka the Eaton M-locker; as shown above). I know of what I speak; I had a 2006 3500HD for a decade and serviced the diffs a couple of times. That "Gov-Lock" was not-so-affectionately known as the "Gov-Bomb" because they had a propensity to grenade themselves under severe off-road use; the "locking" function was so fast and harsh they often just exploded the internal goods when used hard. On-road, they last a fair bit longer. In theory, they should be a good unit. In reality, they were a bit of a risk.
In a simplistic description, these Gov-Lock (M-Lock) units are a limited-slip clutch system when in "normal" mode; the clutches are always slipping to allow the differential to have a low bias for normal daily driving. Then when high-bias is needed, the flyweight locks immediately upon a 100rpm delta (as seen in the video), and those cam-ramps slam the clutch pack tight, causing a shock to the internals and the axle. Oddly enough, though it's called a "locker", it's still just a clutch pack and enough driveline torque can still overcome the clutches, so it ends up slipping anyway, (or shattering components internally).
When new(er), the Gov-lock can provide some fairly high bias in "lock" mode. But as the clutches wear, the have almost no bias in the normal mode and not much more in the "lock" mode (essentially, they don't "lock" nearly as tight as they did when new). This is all because, at its core, it is in fact a limited slip unit and not a true "locker". (not like an air-locker or Detroit locker).
*******************
OP; yes the Mobil 1 gear oil has some L/S friction modifier additives and would be fine to use.
