Front/Rear Diff Change Oil

I've been going through dozens of differential threads.

I know my 2021 TRD Off-Road needs 75W-85 GL-5 or equivalent based on the manual. Where it gets confusing for me is all the back and forth on some of the threads about the differences between weights and GL-4 vs 5, etc.

So... a couple questions...

First, this is my first time changing these oils myself at 36,000. I don't want to void any warranties or any of that fun stuff. Amazon has a good deal going on for Valvoline Full Synthetic

$29 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 Gear Oil in the squeeze packs. It says it meets the requirements of GL-5. Would this be ok to use? I see debates going on between multiple people so I'm not sure.

Second, is there a "good, better, best" when it comes to diff oils and what brand is better than the next?

Third, I see a lot of people commenting on the pain-in-the-ass fill bolt on the front diff. I've also seen people saying to switch it out. What's a good one to switch out to?

And lastly, what's the difference between GL-4 and 5?

Appreciate all the help in advance!

 

Yes. It will be fine to use it.

As for the warranty. I thought it was only good for 36k?
Did you get an extended warranty?

If so, they'd have to to prove that using the "wrong" weight caused any issues.
And 5 point (85->90) isn't going to make a difference.
Not changing it will make more of a difference.

No good answer here.
Pick a name brand top tier and you will be just fine.
What you have listed above will work.

https://www.tacomaworld.com/threads/front-diff-drain-bolt-upgrade.811984/#post-29124683

https://blog.amsoil.com/the-difference-between-gl-4-and-gl-5-gear-oil/

 

Any national brand gear oil is fine for the axle application.
In this case using a

$29 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 instead of the 75W-85 should be fine as well.

GL rated oils, or more correctly the additives in the oil, are exceptionally good at staying in place (protecting) under the twisting loads that are common in an axle. The additives are called Extreme Pressure additives, sulfur is a common one thus the strong sulfur smell gear oils often have.

Take a good look at the ring & pinion gears below, notice the angle of the teeth on the ring gear and also the spiral look of the pinion?



The gears are made that way to give more contact area, it makes the gear stronger (and quieter) than a straight cut gear.
Now visualize how the gear teeth would twist as they meshed and think of the tremendous friction it would create.

Gear oils are compounded to protect against this twisting friction, the additives are designed to stay on the gear, the higher the number the better the protection. For an axle -- so far, so good.




The gears in a manual transmission aren't subject to the twisting forces found in an axle application.

The manual transmission in the Tacoma specifically calls out a GL-4 oil, the reason being that the "better" GL-5 oil is so good at staying on the surfaces it has been discovered that it microscopically rips bits of metal off the brass/bronze synchronizers when shifting, this causes rapid wear on them.

This is called "yellow metal erosion", yes - the oil is "so good" it causes damage.

 

I had Valvoline Full Synthetic

$29 Mobil 1 104361 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 Gear Oil on the shelf so that is what I used 20K miles ago in my front and rear diffs. You should fine too.

I did use the expensive OEM fluid in my transfer case though.

https://parts.elmhursttoyota.com/oe...BjD2es3ndud4yqmOIyLWqLTJPg7WLxq3CLwuN9dE4XFyc

 

East coast gear supply recommends Dino instead of synthetic for diffs
https://eastcoastgearsupply.com/ft-2536-ecgs-gear-oil-recommendation.html

 

I use the same brand. Save your used squeeze packs and get a bulk box of it from wallyworld next time to refill the packs - saves a lot that way.

 

I always swap my front drain bolts on all toyota/lexus to the 90341-24016. You can get it at a Lexus dealer or online. It uses a 14mm head instead of the hex. The fill is also available in 14mm, but I don’t bother. It’s usually high enough to not rust on. Just dab some grease in the hole once done to keep it clear of debris and rust for next time. Make sure to pickup a washer kit for all the various housings to reduce galvanic corrosion as well.

I use redline 75W-85 because I can pick it up at O’rileys usually with a discount. I do save the squeeze packs to refill as it’s faster than a pump. Changing more often is more important than the brand. Try to avoid gl5 in the transfer case when changing at 60k.

 

I found the front drain bolt comes out easily with an impact wrench. By hand it's a pain. Just don't use an impact to reinstall it.