Rear Diff Gear Oil Change - What do you think?

[87Octane]

04 Tundra AC 4x4 TRD w/LSD

w/52k I decide to change rear diff fluid. After reading quite a few posts on the subject, I wasn't totally confident to switch to synthetic due to some posts suggesting EATON posi might not like it. EATON website recommends MINERAL OIL based fluid and GM or FORD LSD additive.

Go to Toyota dealership and ask service for their input, they don't know anything about synthetic, they say all they use is 80W-90 dino and it costs about $60 for the service.

I decided to be conservative and shopped around until I found the Valvoline Dura Blend (synthetic/dino blend) 80W-90 with all the API GL-5 blah, blah, blah ($6). Going by the price, I'd say there's more dino than synthetic which I think is great for this application. Bottle says nothing about any friction modifiers included so I go to GM dealer and pick up the GM 4oz. liquid LSD additive ($6). I saw the LubeGaurd LSD additive is a paste (like in a toothpaste tube) and for the same price thought the liquid would mix quicker and the GM dealer swore that the stuff worked like magic. Test drove, no chatter, not a peep coming from the gears, I'm satisfied.

Like others report, when I took out the drain plug w/magnet there was a sliver of metal about 1/2" long stuck to it and some creamy fine metal particles (not much at all). Not concerned about excessive wear or abuse from previous owner.

BTW, bought the Castrol Syntec (full synthetic) 75W-90 ($8) for the front diff and transfer case - next weekend. Didn't see any posts concerned about full synthetic for these locations.

There's three crush washers and a copper washer for the front and rear diffs ($8) at STEALERSHIP! Transfer case can reuse the existing washers.

Has anyone else gone this same route?

[rakent]

I'm running the exact same stuff, Valvoline Durablend 80w-90 API GL5. The bottles I bought indicated the oil already had the LSD additive, so I didn't put any in. I thought this was the best compromise between full synthetic 75w-90 (definitely not recommended due to both viscosity and being full-synthetic) and a straight SAE 90 weight.

I've put about 10k on it so far (25k on the truck) and no problems. No chatter from the LSD, so there apparently are friction modifiers in the oil. I'll change it again at 30K.

[87Octane]

I rechecked the bottle and other than it saying compatible with conventional or limited slip it doesn't mention friction modifiers. Neither does the Valvoline website. That's why I added LSD additive. Perhaps they've changed the product.

I wonder if the synthetic in the blend allows the clutch plates to slip enough to prevent chatter. So did I go overkill with the extra additive? What harm could occur?

Do I simply punch it off the line or in a corner to be sure both tires are getting equal power or is there another test to see if my LSD performance is compromised?

[derone]

Yeah, put one tire in the dirt on the side of the road and one tire on the pavement. If the one on the pavement spins after hitting the skinny pedal, all is well.
Doug

[rakent]

I believe the oil has the necessary modifiers or otherwise meets spec, at least that's what I assumed they mean when they say "compatible with". I'm certainly not getting the chattering you would expect if the oil didn't have the friction modifiers in it. Anyway, my unscientific, seat of the pants observation suggests that I've lost just a little bit LSD performance. This is based on the fact that I think I get a little more wheelspin before lockup when making a sharp turn from a complete stop. Nevertheless, I'm still getting good lockup performance and I am completely happy with the choice so far.

I really don't think you're going to hurt anything with too much LSD additive, except perhaps a little extra loss of lockup because the clutches can slip a little more.

[Diego]

I had changed my rear diff oil in my 05 Tundra with LSD to Redline synth 75-90. I found it was TOO slippery and I was not getting enough traction, "lockup" of the clutches in the diff like I was before the oil change. I have heard that full synth gear lube is not recommended for LSD diffs and from my experience they could be right. Not that it would likely hurt anything BUT it just seems like it is too much of a good thing, "less friction" and that kind of defeats the purpose of a LSD diff because it needs a certain amount of friction to work effectivley. I noticed the difference anyway and have changed it back to regular dino gear oil, " for LSD diff " from Toyota and have since restored my LSD performance back to the way it was before.

[87Octane]

I contacted Valvoline tech support and this is what they said after a few emails:

Me: I have a Tundra 4x4 w/LSD rear diff. Does the 80W-90 Dura Blend Gear Oil contain the friction modifiers used to prevent clutch plate chatter in the LSD or should I add 4oz of a brand name LSD additive?

Valvoline: It has the lsd additive in the formulation. You do not need to add any more.

Me: Unfortunately, I added 4oz. of the GM additive before I sent this email. Should I be concerned, I think I have an EATON LSD.

Valvoline: Yes, be concerned, to much lsd additive can gum up parts causing the clutches to stick. We recommend draining out the fluid and replacing it with fresh oil.

Me: Which do you recommend
1: Drain, refill w/non-synthetic 80W-90 and add LSD additive.

2: Drain, refill w/Dura Blend 80W-90, done. As you said, includes proper
additive. What is the percentage of synthetic in the blend?

Does the synthetic itself behave as the friction modifier or is there
another material? I've heard straight synthetic will cause too much plate
slip and the LSD will not function properly.

Valvoline: If you use any Valvoline gear oil it will have the lsd additives. This is our conventional blend or full synthetics. Simply drain and go with the one the best suits your needs.


They didn't quite answer all my questions but, oh well. I did pull off onto the side of the road, one wheel on sand, one on pavement and punched it - only tire on pavement started to spin until I let off the gas, so I guess it's working fine.

Still debating to drain and refill with dino 80W-90 or the DuraBlend again and no extra additive for either.