Transfer Case oil recommendation

[iamdub]

I thought the G80 required certain additives? Also, is it ok to have synthetic for front diff? I did not see that labeled.

Fact check this, but from what I understand, RPO "G80" just means it has an LSD but it doesn't pertain to a particular kind of LSD. The one in the older cars or smaller trucks is a certain style (clutch style?) that requires a special friction modifier additive. The LSD in the full-size truck and SUV operates differently and standard gear oil is fine. I'm 100% a fan of synthetic and will always use it where possible and appropriate, but I don't know enough about the front diff. It may vary depending on the type you have (Auto AWD, standard 4WD, etc.)

 

[HiHoeSilver]

Fact check this, but from what I understand, RPO "G80" just means it has an LSD but it doesn't pertain to a particular kind of LSD. The one in the older cars or smaller trucks is a certain style (clutch style?) that requires a special friction modifier additive. The LSD in the full-size truck and SUV operates differently and standard gear oil is fine. I'm 100% a fan of synthetic and will always use it where possible and appropriate, but I don't know enough about the front diff. It may vary depending on the type you have (Auto AWD, standard 4WD, etc.)

My understanding is that G80 is G80, as in, an Eaton G80 aka GovLoc. It is a unique beast in the fact that it functions as a limited slip differential and a locker, which it does mechanically based on wheel slip. Lots of good videos etc. on how it works.

As for the friction modifier.... that's another argument altogether. The Delco fluid and others (Royal Purple and I think Amsoil) have the additive in them already. Many sources say it's not necessary, as well. TONS of discussion and opinions on this buried in the forum.

 

[iamdub]

My understanding is that G80 is G80, as in, an Eaton G80 aka GovLoc. It is a unique beast in the fact that it functions as a limited slip differential and a locker, which it does mechanically based on wheel slip. Lots of good videos etc. on how it works.

As for the friction modifier.... that's another argument altogether. The Delco fluid and others (Royal Purple and I think Amsoil) have the additive in them already. Many sources say it's not necessary, as well. TONS of discussion and opinions on this buried in the forum.

...Which is why I started out with "fact check this.." !

 

[swathdiver]

On the 1500 GMT800 and GMT900s the differential is the same regardless of whether it is a 4x4 or AWD setup. What makes them different is the right axle with the fork and actuator on the 4x4s whereas the AWD models is plain.

A '72 Buick had a G80 in its 12-bolt rear. My Buick GNs all had G80 RPO for their 10-bolts as well. The difference in the truck G80, since the middle 1980s, is that their G80 is a combo LSD AND LOCKER. I had an old bottle of rear diff fluid for the truck with the "new grape scent" that said the LSD additive was included. My later bottles do not say this. No chatter on either.

 

[Rocket Man]

Fact check THIS: my understanding is the new synthetics don’t need a friction modifier and that’s why it doesn’t state on the jugs a damn thing about it anymore, including the AC Delco. It’s because it isn’t added to those fluids anymore. Ahh the beauty of synthetic.

 

[intheburbs]

Can't see why not. @dross99_si is about to do his and will be using 75W90 for the front.

What do you guys think?

@Galante @iamdub @Doubeleive @intheburbs

Yes, technically the 75W-90 recommended by GM includes the additive. But since the G80 is not your typical limited-slip, it's really not necessary. Normal limited-slips have clutches that slip every time you turn the wheel. I've personally experienced clutch chatter in a standard LS rear end. The clutches in the G80 aren't packed that tightly, so you don't really need a friction modifier.

And synthetic fluid is considered an upgrade/improvement, so no harm done if you use it in the front.