GL-4 vs. GL-5 rear differential oil

I have some

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

75W-90 GL-4 full synthetic gear oil hanging out in the garage. Is it good to put in the rear diff? 2017 TRD Sport. I know it recommends GL-5, just wondering if GL-4 would be ok?

 

Stick with the Toyota specifications, they have the engineers.
The GL-4 doesn't offer the wear protection of the GL-5.

The GL-4 is recommended for manual transmissions, specifically the Tacoma manual.

 

Unless there’s something special about the Gen 3 diff that I don’t know about, I don’t see what GL4 would Hurt?

AFAIK, It’s GL5 that can eat away at bronze bushings, not GL4.
And even then, there isn’t any bronze in the differential that I know of?

 

Well, it might not hurt, that still doesn't mean it is a good idea. In an axle application the GL-5 offers the best available wear protection, going backwards is like replacing modern semi metallic brake pads with the cheapest organic pads, the truck will still stop but not as well.

Specifications are determined by engineers, generally it is good practice to follow them.

 

I’m quite sure GL5 is better.
And it’s always better to follow manufacturers recommendations.

Eventually, if you keep the truck long enough, you’ll likely have an axle seal leak.
And when it does, if you’re like me, you’ll go with “any type” over “none at all”

And for those that haven’t had the pleasure of replacing the seal, it sucks.

 

i understand your desire to use what you have but my logic and recommendation is simple. use what the manufacturer recommends. it's not much money to protect a large investment and for peace of mind. to me, it simply is not worth the risk.

 

New diffs cost more than the appropriate fluid.

 

NO

DONE
https://blog.amsoil.com/the-differe...L-4 gear oils are,speed, high-load conditions.

 

GL5 has sulphur in it, which bonds to the surface of iron creating a powerful anti-friction layer on the gears. Sulphur is the same component that chemically attacks the bronze syncros, so is left out in GL4 for transmissions. In a high pressure application like a diff, I’d want to stick with GL5.

 

GL4 does not have the extreme pressure additives that GL5 does. So GL4 will not protect the diff properly. GL5 physically damaged transmissions with synchros but that isn’t relevant to this discussion since it’s the opposite situation being asked about.

 

Cool. Appreciate the help. Looks like I’m headed to pick up some lube

 

GL4 in rear diff:



GL5 in rear diff:


should clear things up