What rear differential oil to use?

FYI stuff doesn't smell good when you change it.

 

85w140, never looked back

 

Hey guys. Im about to do the rear diff myself on my 2014 DCLB SR5. My truck doesn't to much towing at all but when I do get a hitch, that will most likely change. I read 75w90 is the norm. but the dealership said something along the lines of using 75w85. is that a mistake on their part or are they setting me up for failure? Im coming up on 100k in about 4 more oils changes. she stunning good though. Gets pampered every chance i get. Also gotta do the spark plugs so any links to that are appreciated.

 

I just put in 80w90, couldn’t find that proprietary stuff Toyota calls for at any stores.

 

So what do the numbers mean? The higher the better?

 

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No it’s the weight, 80w90 is fine to use.

 

The 2005 Factory Service Manual I have lists specifically 80W-90 for the rear differential. Toyota changed the rear end viscosity to 75W-85 around the same time they switched their motor oils from 5W-30 to 0W-20.

In other words, go ahead and use whatever you want. Use

$30 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90, 80W-90, or 75W-85 if you feel so inclined. Remember these are just gears, all they really need is lubrication (it doesn't care how thick it is). Viscosity plays a much more minor role in a differential than say an engine with VVT-i

 

Thank you for the advice! Info like this helps me make decisions much more easily. I think I will go with the 75w85.

 

Red Line makes a 75W-85 GL-5 rated oil

$25 Red Line 50104, 75W85 GL-5, Full Synthetic Gear Oil - 1 Quart

Link to Red Line 75W-85 GL-5 Gear Oil

That's another important important note.

Whatever gear oil you buy MAKE SURE it is GL-5 rated.

 

AHHH. Ok. Got it! Thanks again!

 

"If you are not hard on the diff, and use syn, then double your change intervals." Y ? Y wood U need 2 change syn 2X regular ? TX 4 any reply.

 

I think he means twice the interval, not half.

 

Doubling your change interval means running the lube 2x as long, not 1/2 as long.

IE if you change at 25k on dino, go to 50k intervals on syn.

 

I read this the other day and I would consider these guys experts

https://eastcoastgearsupply.com/ft-2536-ecgs-gear-oil-recommendation.html

ECGS GEAR OIL RECOMMENDATION
ECGS recommends Dyno (Non-Synthetic) 85w140 Lucas oil with a Ford or Dana limited slip additive for clutch style posi's. The gear oil question is an age old debate that comes down to opinion. We base our opinion on differentials we have seen. Scientifically it has been proven that when measuring diff temps, the actual “metal objects” stay cooler using a quality dyno oil with an additive package over synthetic oils. However it has been proven that synthetic “oils” can stay cooler then dyno oil. So it depends on what temperature you measure the “metal” or the “oil” hence why both can claim they are better.
Other findings, and this varies based on the actual synthetic used: Synthetics thin out quickly once hot and lose their cling ratio to the metal object, when the oil is stuck to the gear it provides a cooling factor for the metal. We also believe that dyno oil has better pressure properties, ie it provides a better cushion then synthetic for two reasons. First, it does not thin out as much and two it clings to the gear.
Another important attribute of differential oil is water separation. A gear oil that will hold its separation from water will protect the differential. It is in our experience that if you add water to a diff with Synthetic there is no clear delineation between the two. On a dyno oil there is excellent water separation properties. Water will ruin diffs as it affects its pressure properties resulting in surface wear quickly, so any oil that keeps its separation properties will outperform one that will not.
An easy not so scientific test is to install synthetic and run your diff for 30 minutes, pop cover and watch how it comes out and feel it. Most we have seen are extremely thin and act almost like water. Same test with Lucas it runs slower and will be stuck to the gear.
All synthetics cost more money than Lucas dyno oil, and I feel there is a risk in what you are getting with synthetic. I find it much wiser to run the lower cost oil and increase the frequency of change. No matter which oil used, the higher the heat in the diff, the faster oxidation occurs and the oil breaks downs. At 140 degrees if no trash or moisture is introduced oil will basically last a million miles. However for roughly every 20 degrees above 140 it cuts life expectancy in half. A well broke in diff under normal conditions will run around 200 degrees and a quality gear oil will last 100k using above formula. However it is not uncommon for differentials to see higher temps when worked hard (steep grades, towing, speed, shock loading, ect.) which is why manufacturers generally recommend 30k intervals normal service and 15k or less for severe service. A differential that is too small for the vehicle obviously sees more strain and thus builds more heat. So an undersized diff under normal conditions will run hotter and require more frequent changes. Other notes on heat: 300 degrees is too hot, 250-270 is normal for a new diff and gear oil should be changed at 500 miles.
In the end comparing gear oil is a useless debate that is tainted by advertisement and claims that aren’t proven, it all comes down to heat and the oil breaking down. Instead of spending $100 dollars on synthetic, spend $20 on Lucas and install a $50 temp gage on your diff. If your diff regularly sees mileage over 200f change the oil frequently, if it doesn't save your money. The flip side to this is synthetic sellers say their oil stays cooler and lasts longer. I think it is false advertisement that can't be proven by the average purchaser. If you ran dyno and the diff regularly ran above 200 it would be worth trying a high quality synthetic oil and proving their claims with a temp gauge.
Opinions on specific gear oils:
Royal Purple: In our opinion one of the worst gear oils made
Valvoline synthetic: Better than royal purple but dyno out performs
Ford synthetic: Probably Valvoline not the worst but think dyno is better
GM synthetic: Similar to ford
Toyota synthetic: Average same performance as most dyno's I think lucas is better
Mobil 1 synthetic: Better than economy dyno's and is likely comparable to Lucas or other quality dynos with additive packages
Amsoil severe duty: Better than all economy Dyno's and all synthetics on the market, but marginal over a quality dyno with additive package
Redline shockproof: Same as amsoil
The only synthetic's I would consider are Amsoil, and redline, along with some industrial synthetic's that aren't really marketed to your everyday user. But would only consider if I was trying to control a heat problem, or shock load issue generally related to doing something the differential was never designed to do in the first place.
In the end changing the oil more frequently will result in less wear and longer life in and will cost less money.

Conclusion Notes:
• ECGS RECOMENDS LUCAS DYNO 85W140 & LUCAS 80W90 FOR EXTREME COLD
• 4 Most Important Attributes to Gear Oil
o Cling Ratio
o Water separation properties
o Cushioning Factor
o Temperature Control
• Temp Reference Chart – oil change frequency
o 170 Deg - 100,000 Miles
o 200 Deg - 50,000 Miles
o 220 Deg - 25,000 Miles
o 240 Deg - 12,000 Miles
o 260 Deg - 5,000 Miles
o 260-300 Deg – 500-1000 Miles until Temp is controlled
• Differential Temp Guide
o 250-275 Degrees is Normal for new differentials breaking in, do not Tow or take long road trips for first 500 miles as this builds additional heat. 300 degrees is to hot and diff should be allowed to cool.
o Normal operating Temp for a differential adequate for vehicle in stock applications 170-220 degrees
o Normal operating Temp - Large tires, Undersized Differentials, Towing 200-250 Degrees.
• Final Notes
o Change your oil frequently your diff will thank you
o If water is ever introduced to differential change it immediately, keep in mind that a differential that is hot and then becomes cool will naturally draw in moisture, so it is not always a water crossing that causes moisture contamination, always run a vent to a dry area and insure it breathes easily.

 

I have been running 80w140 synthetic with moly from Schaeffer's oil with great results. My girlfriend and I both noticed the difference in the rear axle's ability to soak bumps. Much smoother after swapping for the thicker synthetic oil

 

Their position would be better put if they knew the difference between "dyno" (dynamometer) and "dino" (dinosaur, slang for fossil oils)...

 

Don't over think this. Any OTC

$30 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 will be fine. If you like synthetic, M1 is readily available and is affordable. Not really promoting it....it's just easy to get hold of at any parts store....and maybe even Walmart

The gaskets were a $1 a piece at the dealer.

 

Haha The guy has looked inside of hundreds of thousands of differentials, paid for lab testing gear oil in them and your worried about how he spells dino.
I'm not trying to be mean but your position would be better if you worked on differentials for a living and paid a lab to test gear oil in them
https://www.nc4x4.com/forum/threads/gear-oil-heat-break-in-frequency-synthetic-dyno-brand.180539/

 

That's what we used when I worked at Broadway Toyota in Portland back in the day. Actually, IIRC it was 75-140, but I was always surprised by the thick weight, but started using it in my Toyotas and they all responded well. Especially the old ones, actually.