Rear differential fluid

Planning on changing the rear differential oil on my tacoma 2007, automatic, 2.7 4cyl, 4x2.
Any inputs on this amsoil oil? Also, is this de correct oil grade?

second question: transmission oil is a bit dark, planning on changing it also and use toyota oil, any suggestions or comments? Lots of mix opinions on changing transmission oil. Truck has 165k miles.
Thank you in advance.

 

AMSOIL is great gear oil. Factory spec is 75W-85 but not many companies make it; instead most companies make a

$28 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 including AMSOIL. 75W-90 matches OEM spec closer by the numbers but 80W-90 isn't going to hurt anything. All things equal I'd just go with the 75W-90. Been running same fluid in my front, rear, and t-case for many tens of thousands of miles. Blackstone oil analysis tests also show it's good stuff.

Regarding your transmission fluid...

You are going to get all sorts of opinions on that. Generally I think the consensus is that if you smell the fluid and it smells burnt, sometimes it is better not to change it. Otherwise if it is a little dark but not burnt then it's something to consider. The logic behind that is that if the trans is that far gone an on it's last legs (based on the color/smell alone which is alredy making big assumptions), then by draining the old fluid you are removing all the little bits of friction already in the fluid and new fluid can make it slip or fail faster. Again, if it's dark but not burnt smelling then yes new fluid can help but still taking a small chance.

My own personal opinion, as if it were my truck: If it doesn't smell burnt then change it. Fluid is meant to be changed. Fluid breaks down and does not last forever regardless of what someone's great great grand pappy has told them for generations. It's 2024 and fluids are better but they are not everlasting. Just f'ing change it. Toyota OEM fluid is good. AMSOIL fluid is super pricey. Many people have also had success with Valvoline MaxLife but some have also had issues and changed back to Toyota OEM. Again, all opinions, the internet has a bias, blah blah blah. Make your own decision and go with it. If it smells burnt then start making plans for when it blows up.

 

thank you. Great explanation. Appreciate that.
I was a bit confused about the oil grade. I did a research because some places suggest 75-90 and others 80-90 for differential.
Found this info: