Gear lube

[Shikaroka]

I rebulit the 14bolt 10.5" rear end in my Burb last week.
I've got about 1000 miles on it now, with traditional gear oil.
I want to switch out to synthetic now, specifically Amsoil. I also have an aluminum rear cover to install. I believe the cover adds a little more volume of gear oil, but I'm not sure how much.

So, my questions....
What's the best gear oil to use for my Burb that mainly acts as a DD (Daily Driver) and FH (Family Hauler)? I may tow on rare occasions, but probably never over 4000 lbs.
Does anyone know how much oil a polished rear cover adds?

Thanks guys!

[DmaxMaverick]

Aftermarket covers are not all created equal, so the volume is specific to the mfg. Ask them (or read the doc's that came with it), or make a best guess and fill according their spec.

Amsoil "Severe Gear 75-90" is what I would suggest. 75-140 for heavy/frequent towing, but it doesn't sound like that fits your description. Good stuff, and I use it.

[Shikaroka]

That's kind of what I figured, thanks!

Is the "Severe Gear" better (or neccessary) then the standard stuff?

[DmaxMaverick]

That's kind of what I figured, thanks!

Is the "Severe Gear" better (or neccessary) then the standard stuff?

By standard, do you mean dino lube? If so, then yes. In many cases, non synthetic lube is not recommended for GM (and other brands) rear ends. Synthetic has been the factory fill in all GM heavy duty light truck rear ends for many years now. Severe Gear lube replaced the Series 2000 lube, with much improvements and OEM and API compatibility standards. Severe Gear is the one you want. Now, I only recommend dino lube for some limited slip diffs, where synthetic interferes with the L/S operation. I have to use dino lube in my 1985 rear end because that series Auburn limited slip (competition/HP) does not work with synthetic. Wish it did, but it doesn't.

[Shikaroka]

By standard, do you mean dino lube?

Not really. Doesn't Amsoil make a gear lube that is still synthetic that is not the "Severe Gear"?

Either way, it looks like I'll be going with the SG stuff. Thanks!!

[DmaxMaverick]

I guess the term "standard" is a little subjective. They do have other synthetic and semi synthetic lubes, but I would not recommend them for the rear end. An older tranny or gearbox, perhaps. The Severe Gear lube is designed specifically for the diff environment. You could probably get by with the Long Life Synthetic Gear Lube, but I don't recommend it. How much money will you save now, compared to a rebuild later? The change interval for a DD is 50-100K miles for the SG, and about 1/2 to 2/3 that for the other, and less for non synthetic. Lately, I've been running about a 25K interval with the SG, but would be OK going twice that. It's just too easy to change on my '01, it has a drain plug. The lube looks/feels the same coming out as going in. I tow a lot, very heavy (at/near GCWR), and much in 100°+ temps.

[Shikaroka]

Cool, thanks for the advice!

[Shikaroka]

I read a TSB that said you need to use gaskets on the axles if you switch to synthetic because RTV will not hold up to the synthetic gear oil.
Does that sound right?
How about the rear diff cover?

[DmaxMaverick]

I read a TSB that said you need to use gaskets on the axles if you switch to synthetic because RTV will not hold up to the synthetic gear oil.
Does that sound right?
How about the rear diff cover?

It depends on the lube brand. Check with the mfg of the lube for compatibility. Some of them did claim RTV would not be compatible. If your lube is not, use a different sealer, like "The Right Stuff".

[AJMBLAZER]

I've personally never had issues with Mobil 1 synthetic gear lube and RTV and I've been using them on my axles for most of a decade now.

I use Mobil1 synth gear lube in my axles. I can get it most anywhere, it's not exceedingly expensive, and it's quality stuff. I try to change my diff lube every other year if it's just driven around and once a year if it's used heavily. If I get to playing in water I'll change it every time I'm out.

[Shikaroka]

Sounds good, thanks guys.

So, is "The Right Stuff" not RTV?

[AJMBLAZER]

It is, just in a fancy package.

[DmaxMaverick]

Sounds good, thanks guys.

So, is "The Right Stuff" not RTV?

Yes and no. RTV (Room Tempurature Vulcanization) is a basic term for a sealer (generally silicone rubber) that cures at "room" tempuratures. The traditional Permatex RTV has taken on the term as the standard, but it, by definition, could be other types of sealers. Much of the problem with sealer compatibility is the curing solvent/chemical, which is what gives it the unique odor while curing. Permatex has an "Electronic Component RTV" which has a different curing solvent. Apparently, their original product can be destructive to some electronic components. I don't know exactly what it is that can be damaged, but there must be a reason for it. The Right Stuff is a different sealer with a different curing solvent, and I have not seen it react the same with synthetic lubes the same way traditional RTV does.

[Shikaroka]

Ah.... thanks!
It's nice to be surrounded by such knowledgable people.