are gear oil additives good?

Above advice is fine, presuming you have rebuilt it w/new gaskets in the last few years.

Old gaskets need help, and there is radically better chemistry these days on lubricants. I wouldnt' THINK of changing diff oil nowadays w/o putting this in it for seals, heat transfer help, and other reasons.


In fact, I have a Volvo wagon on block waiting for delivery of another bottle of this as I came up short. I'd rather leave the car on stands a few more days to put this in, than use it w/o or jack it up again in a week.

Unless you live in Alaska, also consider 80w-90 as your base lube. I don't want to start a flame war aimed at me, but do the research.
 
I used to buy into all the additives and that stuff. I do feel that some work and have a place. I just can’t see gear oil needing anything added to it with the exception of certain limited slip situations. I drained both diffs on my 86 K20 and washed everything out with brake parts cleaner. I painted the original covers black and reinstalled with permatex gear oil gasket maker and refilled with Schaeffer 75w90. This could have been the first time they had ever been changed.
 
What differential do you have? Is it a basic 2-pinion open one?
I only recommend Redline for differentials and transmissions. My '88 Supra 4-pinion LSD works best with Redline oil. Even the old seals (before I rebuilt the whole thing) did not mind the new fluid.
A good oil to start with needs none of these additives.
 
Only additives I have used in a rear end was Archoil 9100. In a older vehicle I would try Lubegard with a synblend/grp3 gear oil. All newer would get Redline or the 300V Motul Gear ⚙️ oil.
 
I've had my eye on bar's leaks gear repair 1816. Not much info about it out there. Says it repairs gears.

My car came with an empty diff. The gasket change and fill with redline did such wonders I don't think I'll touch it again.
 
I've had my eye on bar's leaks gear repair 1816. Not much info about it out there. Says it repairs gears.

My car came with an empty diff. The gasket change and fill with redline did such wonders I don't think I'll touch it again.
Any product that claims "Repair" or 'rebuild" is making a physically impossible claim and should be shunned.
 
While the product name is "gear repair" a press release I found says:

Bar’s Leaks Gear Repair (P/N 1816) is formulated to revitalize the gear fluid with a proprietary blend of additives. The formula’s seal conditioner protects and reconditions seals, while extreme pressure anti-wear agents provide metal-to-metal wear protection to reduce noise and gear temperatures. A friction modifier helps further reduce noise and wear to improve shifting in manual transmissions and stop chatter in limited slip positraction axles. A performance additive booster includes tackifier and highly sheer-stable multigrade viscosity modifiers to help keep oil on the gears and bearings where it can better lubricate, especially at higher temperatures. And a pour point depressant ensures that Gear Repair will flow even at low temperatures.

Bar’s Leaks Gear Repair extends system life by stopping pinion, axle and other seal leaks, reduces friction and noise, and improves gear performance. The additive also provides superior anti-wear, anti-foam and anti-corrosion protection.


That all sounds really great for the effort and cost. I do still get some grinding and clunking from it at times.
 
While the product name is "gear repair" a press release I found says:






That all sounds really great for the effort and cost. I do still get some grinding and clunking from it at times.
So the product name is deceptive and physically impossible but you still want to use it?
 
I gotta say I thought of this exchange when I saw bar's engine repair at walmart. After trying it I think it is easily worth twice the price of stp grey bottle. Very interested in trying out the gear repair the next time I have the diff open
 
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