Typical rear diff temperature?

[Klutch9]

The vehicle in question is our 2016 Explorer 2.3T AWD. It has a small rear diff for the AWD system, holds like 1.1qts of fluid. I’m going to change out the factory 80w90 when it warms up and I’m doing some homework on what to replace it with. I want synthetic, hands down, but the options for syn 80w90 are limited. I was set on 75w90, but the 40C (104F) viscosities of the two grades are quite different. The 75w90 hovers somewhere around 100 cSt, whereas most 80w90s are around 120-140 cSt, and have a noticeably lower viscosity index in most cases, indicating that they might stay in grade better. Obviously, as the differential gets warmer and closer to the 100C, both fluids would be more similar in weight, but what temp does a rear diff run at? We don’t tow anything, it’s just a people hauler. It’s a simple open diff.

I’m guessing that even at the 40C (104F) rating both fluids are far too thick to be ideal and, if that’s true, I’d lean towards the 75w90.

Not trying to start a war… but there have been numerous threads on here on the 75w90 vs 80w90 topic with little tangible info. If I had a little more info on typical operating temp of the unit, I could then make a more informed decision on what grade fluid to use.

 

[atikovi]

I'd be more concerned with the transfer case fluid. That is a common weak point and they are expensive to replace.

 

[Klutch9]

I'd be more concerned with the transfer case fluid. That is a common weak point and they are expensive to replace.

The PTU/transfer case on the 2.3T is not an issue. It holds a lot more fluid than the V6 models and isn’t scorched by the exhaust. I have replaced the fluid in this already though, 75w140 like the book says

 

[FowVay]

You live in the cold. I'd use the 75W-90. Check out this cool video published by Lubrizol regarding the 75W vs. 80W in cold temperatures:

 

[atikovi]

The PTU/transfer case on the 2.3T is not an issue. It holds a lot more fluid than the V6 models and isn’t scorched by the exhaust. I have replaced the fluid in this already though, 75w140 like the book says

OK, thought they used the same one with all engines.

 

[Klutch9]

OK, thought they used the same one with all engines.

Thankfully, the PTU for the 4-cylinder not only holds more fluid and is farther from the exhaust, it also has a drain plug. Super easy to change the fluid! I drained mine out at 45k miles and although the fluid was very dark, you could still see a very slight yellow tinge if you looked closely.

 

[oldhp]

Redline Oil says 75W90. That's what I would use.

 

[DGXR]

Not severe service so I would go with the manufacturer's spec 75w90. Good to change out the small capacity more often, well done

 

[meep]

I suspect it’s a fairly light duty cycle in this use. 75-90 synthetic would be ideal. It’s not going to spend much time hot.

when towing, the diffs on my trucks easily get so hot you can feel the heat when walking by, and they don’t call for anything special by the factory.

Tales From The Tech Line: Keeping Gears Cool During Break-in

August 11, 2021 - 10:18 AM - Tech Question: I just installed your Yukon limited slip carrier and 3.42 ring and pinion in my GM 10 bolt. I’ve been breaking it in correctly. It’s been about 120 miles so far and it’s still hot to the touch. I can keep my hand on it for about a second or two.

www.randysworldwide.com

and it sounds like the PTU on the transaxle is more particular, AND, yours has the better arrangement in the 2.3. That unit is attached to an actively cooled transmission.

-nice vehicle, btw… had one as a loaner and it made me a believer in the 2.3T. Great drivetrain.