Differential Oil Change, Metal on Plug(s). How Concerning?

Doing a 90,000 mile service on my '03 AC 4WD V8 today, and because it's still fairly new to me I decided to do front and rear diffs and transfer case oils. I have no idea when they were last done, so I want to be sure they're done under my ownership. I did the front diff first, and there was about 1/8" of metallic sludge attached to the drain plug (see photos). The oil was black and stinky. Definitely needed to be changed. What concerns me more is the actual metal on the plug from the rear diff. Again, the oil was black and stinky, but the plug had actual chunks of metal in the metallic sludge (again see photos).
Front diff plug.Rear diff plug.Metal from rear diff plug. Key for size reference.

My question is, how concerned should I be? Especially about the rear diff. I'm not hearing any abnormal noises. No grinding, chattering or slipping, even at WOT from a dead stop. 4WH engages just as it should, and 4WL engages and works fine as well. Is this something I should monitor and do another fluid swap in say, 10,000 miles? Leave it alone? Let me hear your thoughts. Thanks.

 

So I can tell you that I see this all of the time in cars at work when we do the diff fluid for the first time. It’s not abnormal. However, IF your fluid has previously been changed (which you don’t know) then I would say yes, that’s a problem. The fact that your diff fluid was as dark as you say, I bet it’s original. I do mine every 30m and I can tell you that it looks new even after 30k.

 

I wouldn't be overly concerned about that, unless you see it again. I'd assume your fluids have never been changed. That amount of sludge is effectively what I saw. I honestly don't think my fluids had ever been changed either.

 

@shifty` and @The Black Mamba, do you guys think it's worth dropping the front and rear diff fluids at the next oil change (5000 miles) just to be sure? Or just roll with it?

 

If you don't mind spending the money, and it will give you peace of mind, go for it.

 

No. I don’t believe that would be necessary. Don’t loose sleep over it

 

Thanks. And @shifty` thanks for your input as well. I do think it could have been original oil.

 

I bet when you do decide to check it, it will look brand damn new and have no metal whatsoever

 

The Motul SAE 90 Limited Slip and Motul 75W-90 Full Syn was kind of difficult to source, and fairly expensive. So yeah, I'd rather not do that again anytime soon.

 

If you have LSD use Lucas Dino LSD oil. If not use Valvoline synthetic. See posts by Shifty for details.

 

I bought Lucas 80w90 from Advance Auto online using coupon RMN15 for 15% off and had it shipped for free to my front door, if I recall. Easy peasy. And didn’t cost too darn much.

 

Just did mine recently. Looked exactly the same. Guessing original oil.

 

Can probably use speed perks $5 off eventually too!

 

This is what I used to do my rear differential fluid change. No noise or chatter I’m thinking about doing the front in the next few months. What fluid do you suggest for the front diff?

 

I definitely did with my fluids, using old SpeedPerks, and I think I got another $15-25 off from that.

I've refined a small system for saving on gas and parts. Basically, I signed up for SpeedPerks at Advance Auto, and do most of my purchasing with them online (for store pickup), using these coupons on every order, which I almost always get 15-20% off retail with that online order which usually matches or beats scAmazon/RockAuto/Summit pricing. Sometimes Advance Auto will throw the popup in your face for 20% off when you go to the site, and I'll use that.

I then setup an account with FuelRewards using the same phone# I put on my AA Speed Perks account, then linked the two (FuelRewards didn't ask for an absurd amount of personal info, I just gave them my Google Voice number, first initial, last name). Any purchases I make at Advance Auto now give me 5¢/gal at Shell stations AND my SpeedPerks for future AA purchases.

Then, under Fuel Rewards, I linked my debit and credit card, so any qualifying purchases at local restaurants or stores or other stuff automatically add 5¢/gal off. Everytime I fill up at a Shell station, I get discounts. Likewise, I was able to link my anonymously-sourced Kroger Plus grocery card to Fuel Rewards, so every time I buy groceries, I get my in-store discount from the card, and I get fuel discounts.

I typically get ~15-25¢/gal off up to 20 gals every fill-up. One time I got 50¢/gal off. I've only been using the program for a year or two, but basically walk away with 1 in every 10-12 fill-ups being "free" if you factor in cumulative savings. I'm sure someone out there is mapping my preferences and such, to the BS name I gave them, but ... Facebook/IG is probably 100x worse in what they're collecting, and let's not even get into what your internet and mobile services providers are allowed to collect and sell on you after TPTB intentionally killed Net Neutrality for their corporate overlords.

 

I went with Mobil1 full syn 75w110, I believe. Possibly 75w140. In both the front and the transfer case. My front fluid looked ROUGH. But the Lucas is comparable price, I'd consider just running it all-around, honestly.

My xfer case oil looked virtually new. Gold like honey. Be careful not to over-tighten the fill plug on the xfer case.

 

Oh, and FYI it looks like Advance is doing a 20% off right now online, code: SUNSHINE

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Do you know about how much your front dif took? And also rear dif? Planning on doing those today but I need to know how much oil to get!

 

It's in your Owner's Manual, in the specifications section or whatever at the end. It can vary from truck to truck. You should start there, but if you insist on relying on the internet...

You can go to https://www.motul.com/en-US/lubricants

Click on "Cars" icon.
Choose "Toyota (USA/CAN)".
Choose "Tundra (2000 - 2006)".
Pick your exact truck from the Submodel list.

Scroll down in the list to find which item you need to know the capacity of and it'll give you the ballpark so you can add up how many quarts you need of any given product.

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^^THIS^^ But, IIRC front diff 1.1 Liters, T-case 1 Liter, Rear diff 3.2 Liters. Basically until it runs out of the fill hole. The reason I'm using metric is because I used Motul fluids, and that is how they are labeled. The owner's manual does the conversions for you.