What type of rear in oil should I use?

Why is it every time there's a good thread with good info from experienced people some c### sucker has to come out and say some c### sucker **** that is in no way helpful.

Tachyon said:

WTF do you think a GM dealer parts counter is going to do? They're going to look up your vehicle, by VIN, and give you the GM recommended gear oil for the specific rear end installed in your vehicle.

As for synthetic, what are you, one of those "all oil is the same" Luddites? Or did you just not know that synthetics weren't in wide use other than in the Corvette two decades ago when that truck was produced? Just because it wasn't factory then doesn't mean you shouldn't or can't use it. They didn't sell the trucks with premium tires either, do you tell people that putting better tires on their truck is stupid? Or should they only use all season Uniroyals made in 1999?

The fact is that synthetic gear oil is proven better in hot, cold, towing, and performance conditions. Period. And considering how seldom you actually have to change it, it's stupid not to upgrade to it.

Click to expand...

Wow, you sure are losing your mind over my post. Relax buddy. You made a lot of assumptions that have nothing to do with what I said..

But what is fact: if it's a GMT400 truck, barring the 3500HD, it takes 80W90 GL-5. No additive - whether open diff or factory locker-equipped. You don't need the dealer to tell you what it needs, nor do you need to pay their price for gear oil. That's as simple as it gets, so take it easy. Adjust meds. Meditate. Go out to the garage and kick the dog, whatever...

Richard

I hope no dogs get kicked in this !

Tachyon said:

WTF do you think a GM dealer parts counter is going to do? They're going to look up your vehicle, by VIN, and give you the GM recommended gear oil for the specific rear end installed in your vehicle.

As for synthetic, what are you, one of those "all oil is the same" Luddites? Or did you just not know that synthetics weren't in wide use other than in the Corvette two decades ago when that truck was produced? Just because it wasn't factory then doesn't mean you shouldn't or can't use it. They didn't sell the trucks with premium tires either, do you tell people that putting better tires on their truck is stupid? Or should they only use all season Uniroyals made in 1999?

The fact is that synthetic gear oil is proven better in hot, cold, towing, and performance conditions. Period. And considering how seldom you actually have to change it, it's stupid not to upgrade to it.

Click to expand...

WOW, someone's panties are in a bunch... hopefully your just having a bad day... please reread the post you replied to. You both are saying the same thing. BUT, you are saying it like you are the end decision here..

Are synthetics better these days.... sure. Are they NECESSARY, no they are not. It's up to the owner to decide if they want to run it. If they don't "work" the truck regular gear oil, in this case 75/80 or 80/90, would be just fine. If they work it I would "recommend" a synthetic as it does not break down as fast and even go as farcas recommending a 75/140 in regular or synthetic variety.

Bottom line is,
--synthetic is not a must
--Gmt400 platform never came stock with synthetic oil
--regular dino gear oil is fine weather it's regular duty or a heavy worked truck
--in the end it's the owners decision what they run
--no need to try to "force" an opinion as being the right way.
--there are many ways to skin a cat.
--dealer is not always right, as most of stuff, fluid wise, is now backwards compatible so they will try to push the newer fluids even though the original stuff is still easily availible..

Sent from my SAMSUNG-SM-G891A using Tapatalk

So to recap,
#1 Skin a cat
#2 Kick a dog
#3 Replace diff fluid with GL-5 80w-90.

Approx how much does the diff take?

Not sure if I can ship AC Delco oil over here...

Tiny Trucker said:

So to recap,
#1 Skin a cat
#2 Kick a dog
#3 Replace diff fluid with GL-5 80w-90.

Approx how much does the diff take?

Not sure if I can ship AC Delco oil over here...

Click to expand...

Looks as though 3 quarts is what you should get

For the Rear Differential Capacity.....

Rear Drive Axle (8.6") 2.03 liters (2.15 quarts)

Rear Drive Axle (9.5") 2.60 liters (2.75 quarts)

Rear Drive Axle (9.75") 2.84 liters (3.00 quarts)

Rear Drive Axle (10.5") 2.60 liters (2.75 quarts)

Rear Drive Axle (11.5") 3.00 liters (3.17 quarts)

NO FRIGGIN DOG KICKIN !!

Oldblue98 said:

Looks as though 3 quarts is what you should get

For the Rear Differential Capacity.....

Rear Drive Axle (8.6") 2.03 liters (2.15 quarts)

Rear Drive Axle (9.5") 2.60 liters (2.75 quarts)

Rear Drive Axle (9.75") 2.84 liters (3.00 quarts)

Rear Drive Axle (10.5") 2.60 liters (2.75 quarts)

Rear Drive Axle (11.5") 3.00 liters (3.17 quarts)

Click to expand...

(That 11.5" being the Dana 80 in the 3500HD which takes the synth 75w140 as I mentioned earlier.)

(edit - holy crap that little pissing match was 2 years ago? someone liked the post is why I saw it pop back up! oh well; the extra info ain't gonna hurt anybody!)

Richard

Seeing as the thread is reactivated.....
The additives being mentioned - what are they, what is their function?

A GL5 will already have a fair amount of anti-wear additive. Anti-wear additive of the type that attacks 'yellow' metals which is why GL5 can only be recoomended in gearboxes with steel synchro rings and anything with brass/bronze synchro rings should use GL4.

The additional additives (diff) are they anti-wear?

And, seeing as diffs are mentioned by size - what will my 1999 C2500 with G80 and 4.1 ratio have?

The very last GMT-400's would have had synthetic, as the change happened in 99. My truck may well have had synthetic originally. It's running dinosaurs now, Though.... some of which where processed about 40 years ago, since I ran out of my "old" gear oil, while refilling, and used what my uncle had under his workbench.