Differential oil viscosity differences

[L83_Z71]

What's up everyone? I'm fixing to do all my fluid changes on my Silverado 1500 and I have a question about the rear diff fluid. Per the manual it says to use a 75w 85 for the rear and 75w 90 for the front. I can really only find the ACDelco 75w 85 and was wondering how critical it was if I just put the 90 in instead of 85 in the rear diff. Any help is greatly appreciated. 

[HeySkippyDog]

I used 75W-90 Amsoil Severe Gear in my rear axle and it's been perfectly fine.

I recommend the same for you in both front and rear. It's good stuff.

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[L83_Z71]

4 minutes ago, HeySkippyDog said:

I used 75W-90 Amsoil Severe Gear in my rear axle and it's been perfectly fine.

I recommend the same for you in both front and rear. It's good stuff.

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Ok cool, I'll give it a whirl. Thanks

[HeySkippyDog]

It's commonly used here on the forum and there really isn't a gear lube out that does it better.

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[redwngr]

SAE 75W-85 Synthetic Axle Lubricant

SAE 80W-90 Axle Lubricant

 

The one spec'd for the rear is synthetic.

It is the correct lube for the G80.

 

 

 

 

 

 

[Mike GMC]

+1 Amsoil 75w-90 front and rear.

[txab]

75w-90 synthetic all around and never give it another thought

[Jacoby]

I use Redline 75w-110 in the rear and 75w-90 in the front. 

[diyer2]

75- 90 synthetic that meets spec API GL5.

Just change it is all you need.

 

I use this.

 

[Paintor]

Synthetic Gear oil is Hydroscopic.

 

Old school Gear Oil if you have a leak, you will see it on your rear axle for years.

 

Synthetic will wash off driving through your first rain storm. GM will deny fixing any leaks since they can’t see it, washed off.

 

Genius really.

 

 

[Jh8473]

Supertech 75-90

[imiller1974]

On ‎5‎/‎11‎/‎2019 at 4:44 AM, Paintor said:

Synthetic Gear oil is Hydroscopic.

 

Old school Gear Oil if you have a leak, you will see it on your rear axle for years.

 

Synthetic will wash off driving through your first rain storm. GM will deny fixing any leaks since they can’t see it, washed off.

 

Genius really.

 

 

The word you're looking for is hygroscopic. And no it isn't.

[Paintor]

16 hours ago, imiller1974 said:

The word you're looking for is hygroscopic. And no it isn't.

That’s the word. And yep it is.

 

Pour some Synthetic gear oil on your sidewalk and watch what happens.

 

Washes away. Or just ask Google.

 

GM had to switch from Crude Oil to Shale Oil-synthetic cuz Fort Knox ran outta Gold. Synthetic Gear Oil aint superior to Gear Oil.

 

Only 1 can be defeated by a pressure washer.

 

[Hillwood]

On 5/22/2019 at 5:54 AM, Paintor said:

That’s the word. And yep it is.

 

Pour some Synthetic gear oil on your sidewalk and watch what happens.

 

Washes away. Or just ask Google.

 

GM had to switch from Crude Oil to Shale Oil-synthetic cuz Fort Knox ran outta Gold. Synthetic Gear Oil aint superior to Gear Oil.

 

Only 1 can be defeated by a pressure washer.

 

You saying Synthetic like AINT superior.? Regular is better because it won't wash away when it leaks?

What does this have to do with the internals of the gearbox?