More Amsoil Black Gear Oil

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Sep 18, 2002
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Some of you may be aware of my rear end saga on my 2002 4Runner. "Apparently", one mechanic ago was a little shy on my gear oil
and it burnt up my rear differential. It came out black. Got a new rear diff from ECG supply and had everything from the brake shoes from one side to the other side replaced. Diff from ECG and all the other were Toyota OEM parts. About a $3000 job in total.

I got it back 500 miles ago and just for kicks decided to check my fluid this afternoon. Went on and drained it (Amsoil 75W-110) with about
1000 miles on it and it is black as tar. Looks like you poured graphite in it. I drained out 2.5 qts.

Did I get a bad batch of gear oil? Thank goodness I saved a sample this time. There is no way this is a low fluid situation. I called my "new"
mechanic and he's thinking I have a gear oil issue. Is Amsoil supposed to turn black?

I'm an Amsoil fan boy and this is not a slam. It seems to me I have a problem.
 
Between the two I would trust Amsoil. Is there a magnetic drainbolt or is it dropping a pan? Wondering if there’s anything on the drainbolt
 
My Chevy has a carbon clutched diff…at least that’s how I think it is described.

In any case the proper fluid goes in colored like melted butter, but comes out 45,000 miles later as black as BLACK paint.
 
Some of you may be aware of my rear end saga on my 2002 4Runner. "Apparently", one mechanic ago was a little shy on my gear oil
and it burnt up my rear differential. It came out black. Got a new rear diff from ECG supply and had everything from the brake shoes from one side to the other side replaced. Diff from ECG and all the other were Toyota OEM parts. About a $3000 job in total.

I got it back 500 miles ago and just for kicks decided to check my fluid this afternoon. Went on and drained it (Amsoil 75W-110) with about
1000 miles on it and it is black as tar. Looks like you poured graphite in it. I drained out 2.5 qts.

Did I get a bad batch of gear oil? Thank goodness I saved a sample this time. There is no way this is a low fluid situation. I called my "new"
mechanic and he's thinking I have a gear oil issue. Is Amsoil supposed to turn black?

I'm an Amsoil fan boy and this is not a slam. It seems to me I have a problem.
UOA. Test it.

I doubt amsoil would put a bad batch out. More likely you have something mechanical going on that needs addressed. As black in gear oil typically means oxidation is happening somehow.
 
Well, at ECG Supply they used Lucas 85W-140. I ran that for 1000 miles. It came out a clear brown. What I expected.
I replaced after 1000 miles with Amsoil 75W-110 and it has been about 1000 miles since that change. I'm thinking
all the black would have been washed out with the Lucas conventional. Maybe not? Maybe it is merely the synthetic
cleaning out any residue that the Lucas didn't touch.

It does not smell burnt. I think I'm getting nauseous....s

Anyways, I added 3 qts of Amsoil from another batch. Just to see.

Whom can I trust with this sample?
 
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UOA. Test it.

I doubt amsoil would put a bad batch out. More likely you have something mechanical going on that needs addressed. As black in gear oil typically means oxidation is happening somehow.
I agree. That's what my Amsoil dealer said. Check for oxidation.

It's weird we blamed it on low fluid before. Maybe it wasn't low fluid?
 
My only thought is the oil has picked up junk from before the rebuild. I recently rebuilt the axle in one of my trucks and cleaning it out was a tedious job. The axle tubes required swabbing several times to get all the mess out of.
 
Don't freak over the red. This is the same measuring container I drain my ATF in.

This is a cold drain. Not driven in 24 hours.
 

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My only thought is the oil has picked up junk from before the rebuild. I recently rebuilt the axle in one of my trucks and cleaning it out was a tedious job. The axle tubes required swabbing several times to get all the mess out of.
I'm hoping. Makes sense. This Severe Gear is expensive at 3 qts/drain.
 
I'm an Amsoil fan boy and this is not a slam. It seems to me I have a problem.

The antioxidant in the AMSOIL SVG 75W-110 turned black due to high temperature. Do a couple more oil changes like 200~300 miles apart and make sure you drive a decent amount of miles on the highway. If the color doesn't lighten then I would worry. At this point, maybe it's just break-in induced heat. I had something similar happen with the front diff in my 2022 Dodge Durango GT Plus AWD.

As black in gear oil typically means oxidation is happening somehow.
Bingo! It's due to heat. My wife's Jeep GK WK2 has a MP3023 transfer case, so it drives the rear wheels primarily and uses a clutch to engage the front only when it detects slippage, which it never does. Unless I engage 4WD Low or one of the "driving modes", the front wheels aren't driven. The problem is that our Jeep has a "baby" rear diff. I can barely shove a quart of gear oil in there. It's got no cooling whatsoever. It turns any oil dark after a few hundred miles, well, depending on the formulation of course. Something that has more antioxidants in it will turn black quicker.

Ah, @Gebo: Take two or three layers of show towels and filter the oil through it. If there is no metal in it, you're fine, it's just heat. It will take forever to filter it through 3 of them, but it's worth it. I did it on the Jeep. Good luck!
 
@Gebo - Get some Delvac 1 75W-90 from Summit Racing at $39.99 a gallon and run it for a while, it stands up to heat pretty well. I assume you have an open diff. Then go back to AMSOIL.
 
Thanks Rod Knock. If it is heat induced why didn't the Lucas 85W-140 turn black?
 
I would've broken it in with some 75w140 from walfart or local autopart ripoffstore. After break-in, drain and fill with your favorite boutique gear oil.

I'd also wager that its normal gear contact hot spot cooking. We'd run automaker production gears on a contact die to create a smoother/harder pre-broken in surface which reduced assembled break-in time drastically, lowered the amount of metals shed, while reducing the oxidation of the gear oil since very few automakers recommend early diff changes. You won't see that from aftermarket gear sets.

Once its all self-machined and worn in smooth, if its built correctly, all should be good.

What limited slip is installed? Who installed the Amsoil?
 
Thanks Rod Knock. If it is heat induced why didn't the Lucas ?W-140 turn black?
As previously stated, the antioxidant is what drives the color change. The higher the temperature, the darker the gear oil turns. I have a pretty bad opinion about Lucas in general because they cut corners and mislead customers. My two cents is that they skimped on some additives in their gear oil, as it's par for the course with them. I think that AMSOIL did its job and wouldn't worry about it. Neither should you worry about Lucas, just don't use it again. ;)
 
If you really think it was a problem with the brand I would contact Amsoil directly. I doubt if anyone on here would know if you got a “bad batch.”
You never know. I have already contacted my dealer. Gotta get a sample.
 
I would've broken it in with some 75w140 from walfart or local autopart ripoffstore. After break-in, drain and fill with your favorite boutique gear oil.

I'd also wager that its normal gear contact hot spot cooking. We'd run automaker production gears on a contact die to create a smoother/harder pre-broken in surface which reduced assembled break-in time drastically, lowered the amount of metals shed, while reducing the oxidation of the gear oil since very few automakers recommend early diff changes. You won't see that from aftermarket gear sets.

Once its all self-machined and worn in smooth, if its built correctly, all should be good.

What limited slip is installed? Who installed the Amsoil?
ECGS broke it in with Lucas 85W-140 for 1000 miles. That's what they did. ECGS did the install. I did the Amsoil.
 
As previously stated, the antioxidant is what drives the color change. The higher the temperature, the darker the gear oil turns. I have a pretty bad opinion about Lucas in general because they cut corners and mislead customers. My two cents is that they skimped on some additives in their gear oil, as it's par for the course with them. I think that AMSOIL did its job and wouldn't worry about it. Neither should you worry about Lucas, just don't use it again. ;)
Just so are all on the same page. ECG installed the Rear diff $1300 and they used the Lucas 85w-140. They said to drive it for
1000 miles and then change it. The gear oil looked fine as I drained it. I replaced it with the Amsoil 75w-110 about 1000 miles ago.
Checked it today and it is what the pics show. I would never use Lucas but I felt I had to go with what ECGS said.
 
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