Rearend fluid Change

[WindyCityPilot]

I’m planning on swapping the fluid in my rearend with a synthetic fluid. I have not decided on which fluid yet (Mobil 1, Amsoil, Royal Purple…..) but my question is do I need any additives for the G80 rearend? I know they have friction modifiers out but I’m not sure if I need to add them with the G80 rearend. I've done a few searches but have not found anything that addresses this exact question.

 

Thanks!

[Butch 02 Denali]

Since you are using synthetic fluid, it has the friction modifyers already in it. No need to add more unless the clutches chatter on low speed corners.

[WindyCityPilot]

Since you are using synthetic fluid, it has the friction modifyers already in it. No need to add more unless the clutches chatter on low speed corners.

 

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Thanks for the quick response! I was reading somewhere else that my '06 came from the factory with sythetic fluid in the rearend. Any truth to that?

[jwhjr]

Thanks for the quick response!  I was reading somewhere else that my '06 came from the factory with sythetic fluid in the rearend.  Any truth to that?

 

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Yes, they come from the factory with synthetic in the rear end.

[Shotgun]

Using Royal Purple here. Friction modifiers not needed.

[01z71]

I am running Amsoil 75W90 Severe Gear Synthetic Fluid. The first time I changed my rear end fluid I used the GM Grape Stuff.

 

Other than being out a lot more moeny I can tell no difference between the different synthetics. I change the fluid once a year and it comes out just as good as it went in.

 

and yes, the '06 and other years come with the synthetic in the rear end.

[pm26]

  The first time I changed my rear end fluid I used the GM Grape Stuff.

 

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GM grape stuff is very appropriate name for this oil, becuase it costs as much per quart as a premium French wine.

[camshaft]

Use Royal Purple. I think mine (05) took 2.75 quarts, and 1.25 in the front. I noticed an increase in mileage immediately.

 

Have fun.

[flyer]

The Eaton G-80 does not require any additives. From Eaton's web site (http://www.automotive.eaton.com/product/traction_stability/lockingdiff.html):

the G-80 is "Maintenance free; requires no lube additives".

 

My owners manual does not specify any additive for the rear fluid.

[pm26]

Use Royal Purple.  I think mine (05) took 2.75 quarts, and 1.25 in the front.   I noticed an increase in mileage immediately. 

 

Have fun.

 

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I somehow do not think that your perceived mileage increase was due to introduction of different oil in the differentials. (unless you used extremely low viscosity oil) If you stayed with 80W90 I doubt you would see any effect on mileage.

[camshaft]

I have tracked my mileage since day one. And yes, I can honestly say that when I switched my rear dif, front dif, and transfer case the mileage increase was noticeable. This is fact, not "perceived"

 

I'm not saying that everyone's truck will react the same way mine did, nor do I really care. I simply went with Royal Purple beacuse of the numerous posts I read about other people having an increase in mileage as well.

 

For my truck, it was a great benefit....that's all I'm saying.

[Black02Silverado]

I’m planning on swapping the fluid in my rearend with a synthetic fluid.  I have not decided on which fluid yet (Mobil 1, Amsoil, Royal Purple…..) but my question is do I need any additives for the G80 rearend?  I know they have friction modifiers out but I’m not sure if I need to add them with the G80 rearend.  I've done a few searches but have not found anything that addresses this exact question.

 

Thanks!

 

 

 

 

 

 

Any of those quoted above will work fine. Way cheaper than what GM puts in there.

[bigdogxx]

Glad i seen this post, my dealer just called me the other day stating at the 15k mark i need to service both diffs and trans case.Is 15k the right interval for changing these fluids, i always thought diff fluids went atleast 25k+ before needing a change. In any case i would probably be better off having my regular mech do it then the dealer because i heard that gm trys to charge 50+ dollars per quart or something crazy like that, is that true?

[pm26]

Glad i seen this post, my dealer just called me the other day stating at the 15k mark i need to service both diffs and trans case.Is 15k the right interval for changing these fluids, i always thought diff fluids went atleast 25k+ before needing a change. In any case i would probably be better off having my regular mech do it then the dealer because i heard that gm trys to charge 50+ dollars per quart or something crazy like that, is that true?

 

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Unless you abuse the crap out of your truck offroading or towing heavy trailers ALL the time, 30k is the minimum interval I would even consider for changing the differential fluids. In fact, for normal road use, I would even go to 60k mile interval. 15k interval would be an overkill even for severe service, which is quite frankly constant abuse of the truck.

 

BTW, the cost of synthetic GM rear end lube is about $ 24/quart (list price). 3 times more expensive than comparable synthetic brand name gear oil, such as Redline of Mobil1.

[asepgrad98]

Is 15k the right interval for changing these fluids

 

GM does recommend changing the rear gear oil after the first 500 miles of towing. I would go ahead and at least change that fluid.