Gear Oil?

Does the viscosity matter for rear diff oil? My manual states:
Front Diff: SAE

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

75w-90
Rear: Above 0 degrees F- SAE 90
Below: 0 degrees F- 80w-90 or SAE 80W.

All I can find locally is 75w-90 and 80w-90.
Thoughts? We get below 0F a couple times a year.

 

Actually all I can see locally is the 80w-90.

 

Most folks just run a high quality

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

75w-90 in the diffs and T-case such as AMSOIL Severe gear and call it a day with no issues, myself included.

 

Canadian tire has the

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

75w-90 Royal purple but $30 a quart.

I just did the rear axle seals I should only need a quart?

 

^Cheaper option if you have a PartSource close by (same company as CT): https://www.partsource.ca/products/0280244-mystik-jt-7-synthetic-blend-gear-lubricant-75w90-946-ml

 

Royal Purple is pretty decent, IIRC the rear calls for closer to 3 or 4 quarts but I never go by volume, keep putting it in the fill plug hole till it just barely starts to dribble out, that's the "full" line.

 

OP,
I found the linked info from ECGS on gear oil very enlightening. It may be worth your time to read as well, maybe even save you some money. Take a look: ecgs-gear-oil-recommendation1.pdf (eastcoastgearsupply.com)

 

good find but they are out of stock in my area it says.

 

^80W90 is fine. 75W140 is good too - it's what I use: https://www.canadiantire.ca/en/pdp/pennzoil-full-synthetic-gear-oil-75w140-946-ml-0280200p.html

 

Thats interesting. They recommend the Lucas. I see their

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

75w-90 is labelled synthetic would their 80w-90 be their dino oil?

 

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

75w-90 or 80w90 will be fine.
They are both a 90 weight oil.

The only difference is how they flow cold.
And the differential won’t stay cold long enough for 5w point to matter.

I used 85w-140 in my front differential.
If I were to do it over, I would have just used 75w-90.

I’m using 80w-90 in my rear differential.
We don’t get below 0. About the lowest we see is low teens.

We might see single digit or near 0 once every 50 years.

 

Yes, the 80W-90 is a HD dino oil. And it probably has a very similar additive package to the 85W-140 HD Lucas dino oil that ECGS thinks so highly of. Given your climate, the 80W-90 HD Lucas dino oil would be a very good choice IMO. The 85W-140 HD Lucas dino oil is what I will be picking up tomorrow for use down here in MS. I have used both Amsoil and Red Line synthetics. Both were very good gear oils.

 

Here is my experience with the heavier oil.
I’m not the only one to have this happen.
If it gets below 50 degrees where you live, I’d maybe stick to 90 weight.
https://www.tacomaworld.com/threads/front-diff-leaking-gear-oil-from-the-breather.744067/

 

I have some Lucas 85-140 fs….if it’s what you’re looking for and it’ll save you a few bux…. (Although not sure w shipping)
https://www.tacomaworld.com/threads/fluids-randoms.761843/

 

Amazon will ship Lucas 80w-90 dino to you but now like $18 a quart so Advance or Autozone also ship about $13 a quart.
Mobil 1 in

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

75w-90 syn is everywhere also.

 

Just changed my 2016 rear diff oil at 95K mi. It was still clear and gold. Unlike any other disgusting stinky black gear oil Ive ever changed. Manual says GL-5 Synthetic. I went back with Mobil1 80-90W Syn. Super easy change. 4qts didn’t fill to the fill threads but I measured what came out and it was only 4qts.

 

Bit of an odd article. Says lucas dino is better than synthetic oil, than says serval synthetic oils perform as good as or better than dino lucas. Interesting statement about heat and diff OCI, I had always thought that the increased resistance to flow, from a thicker oil, would increase the heat of the fluid. Guess I would need to see some data.

 

Rear Diff capacity is 3.1 qts (or when it comes out the fill plug) but not 4.
Front Diff 1.6 qt
Transfer Case 1.1 qt

 

I ran into this same issue on my 08 with limited slip. Lucky I found that Mitsubishi makes a SAE 90 gl5 for the evo for around $15. My truck chatters at start if I use 75-90.

 

thats odd, on Amazon i picked up a gallon of lucas 80w90 for $32