Low Rear Diff fluid symptoms?

You want to know what’s weird?
Valvoline

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

75w-90 is synthetic based.
Yet 80w-90 is NOT synthetic based.

There has been numerous reports of synthetic base gear oil causing chatter in the mechanical LSD trucks.
My vote is, use 80w-90 and run an LSD additive.

Will it hurt it?
Nope, not at all.

Go read your owners manual, it never calls for 75w-90 in the rear differential.
It says, 90w, 80w or 80w-90.

 

i used this when i did mine. TW members informed me I don’t have a tru LSD and didn’t need it. When Toyota did my diff they used an friction modifier.

 

Friction modifiers won’t hurt an open differential. They won’t help either.
But if you add it to all the fluid, you can never make the mistake of not using it if need.

I think the dealership does it as a safety measure.

 

To emphasize the point, only mechanical LSD units require the LSD modifiers. Mechanical LSD’s in second gen Tacomas were installed in certain 05-08 models. It came standard on Sport models. I don't recall if it was an option on non-Sport models. I am curious, do rear lock diffs require the modifiers?

 

No, the locker does not require modifiers.
It’s fully open until locked. And it’s physically locked. Modifiers have no bearing on the locking system.

 

Just purchased some today. Do you think I can just add it to what I just put in? I just replaced it not too long ago and really don’t want to drain it again and buy it all over again if I don’t have to

 

Yes, you should be able to add it in. You shouldn’t have to drain it.

You might have to suck a little diff fluid out if you filled it correctly.

 

Once you add the friction modifer find a open lot and do about ten figure eights to work it into the plates

 

And was the truck level, side to side and front to rear. If not any checking is less than accurate.

If nose down or off side to side you can add too much. If nose too high you can't get enough in.

 

Let's assume the Valvoline fluid you used is the best you can buy with all the additives you need: That said: There are no symptoms until it whines, howls and fails.... (you'll know) Remove the filler plug on a level area when it's cool, and see if you get a steady stream out of the opening. If you don't: it's not full. Add fluid accordingly.

 

Thinking broadly and with the cold weather, do you use your parking brake often? If so, maybe it’s sticking.

 

So I just added it today and I am stoked. Drove it around and it was a night and day difference. It no longer does anything and drives beautifully. Idk if it’s placebo but the vibrations are definitely gone. Thank you and everyone for the input. I really appreciate it!