Rear differential fluid

Can cause seal failure.

Lots of people running synthetic end up blowing out pinion seals or axle seals. The more sliperry the fluid, the easier it can leak.

I had it happen to me and East Coast Gear Supply told me to run Lucas 85-140w conventional in my drivetrain. Switched to that and have had no issues since.



Horror story, i ran synthetic in mine (BG synthetic) and my pinion seal failed. Had a shady shop replace it because i was afraid to do it myself. Less than 10k miles later my pinion bearing failed because they didn’t set the backlash on the pinion properly when they replaced the seal (VERY IMPORTANT that the nut goes back where it was!!!). Ended up replacing the whole third member (center section) with a new one from ECGS.

EDIT:
I have since learned more about toyota factory rear ends. They use a crush sleeve on the pinion to set the backlash from the factory. This is a one time use item. So, that means if you take the pinion apart, you have to replace the crush sleeve or reset the backlash with spacers.

so when i replaced the third member, i replaced it with an ECGS factory replacement with spacers instead of a crush sleeve. 1000% better.

 

Here’s a great video of a walk thru, it’s super easy.
https://youtu.be/jNWzQ2MbcX0

 

Wrong. Sample size n=1 does not mean everyone that runs synthetic will blow axle seals as a result. You run conventional and rarely change it for 150k+ miles and then switch to synthetic? Sure, you might see some leaks That are exposed by a change and the inherent proprieties of synthetic. That isn’t the fault of the synthetic, it’s your fault for improper maintenance.

Run a syn at the 30k recommended intervals? Likely Enjoy a functional, leak-free diff for as long as you operate the vehicle.

 

Thats always been my game plan!

 

I have run Walmarts Super Tech

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

75W-90 Full Synthetic in my 2015 2WD Tacoma for about 12K miles and the wifes 2014 4Runner 2WD for about 45K miles. Both differentials are dry as a bone.

 

You must be getting oil squeezed from the finest gears in Japan for that price.

 

For those of you curious as to ECGS opinion, here is the link. I use non synthetic in both my trucks since they both have ECGS built diffs.

https://eastcoastgearsupply.com/ft-2536-ecgs-gear-oil-recommendation.html

 

Hyundai recommends Quaker state motor oil. Ford- motor craft, etc. same situation.

They likely get a discount/and or other benefits for recommending Lucas oil. Notice how it’s not just conventional, but LUCAS conventional? Please.

Run a syn or conventional at the 30k change interval and don’t worry about it. But let’s not go down the “syn will make your diff leak and that we should only use conventional” road. Total hogwash.

 

I'm not worried about it and was simply sharing the link for folks to reference. I'm running four diffs from ECGS and with the difference in pricing across oil brands being negligible I choose to use what they recommend.

 

Negative. Whats wrong is your improper assumption of my mileage. I didn’t even have it in my truck for 20k miles before it started leaking. So you know nothing.

I did not say, “don’t run synthetic.” I said its not recommended.



I said a reputable company, told me, they do not recommend people to run synthetics in toyota differentials. I didn’t develop that opinion solely from my one sour experience. I was given that informed opinion from a company that specializes in drivertrains and has done tens of thousands of these trucks.

I service my shit more often than anyone you know or can bring me. Assumption is the mother of all fuck ups.

 

I run nothing but synthetic. 120K and no seal problems. Runs significantly cooler

 

You have temperature readings to prove this?

 

Not sure what temp mine runs at, how about with the synthetic? How do I measure that?

 

350!!!!! yikes!
the fluid is $40-50 for synth
get 4 of these-
https://shop.advanceautoparts.com/p...COiEwVZHOCl1KeYU0QUaAsw7EALw_wcB&gclsrc=aw.ds

its a no brainer
you will need a 24mm socket, torque wrench & a pan to catch old fluid & replacement crush washer for drain bolt
it will smell helllllla bad...get ready to barf....especially if you are overdue for fluid swap

remove fill bolt first
place pan under drain bolt & remove drain plug & let it drain

drink a beer
examine the drain bolt magnet for large chunks of metal
(there will be a fine gray dust/paste on the magnet...this is normal...any big flakes or chunks could be a sign of future diff issues)
drink another beer
shake the truck (not necessary but always fun)
reinstall drain bolt with new crush washer
refill the diff via upper fill bolt (you will put in more than 3 but less than 4 of the quarts)
fill until fluid is running out of fill hole (steady 1/8' wide stream roughly)

torque both bolts to 40 ft-lb (I believe one is 36 & the other is 40, but I just do them both to 40)

it is most ideal to do this procure on level (or near level) ground

enjoy the fresh lub on the rear end...I always feel slightly more peppy after changing the rear end gear oil

 

as far as the synth convo....
here is my story
I ran the stock factory fluid from 2 miles to 90k miles (I missed 5 rear fluid swaps, as the manual calls to change it every 15k miles)
then I put in valvo synthetic

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

75w-90 every 15k miles (started to follow the every 15k maint guide from 90k to 305k)

never had a single drop of gear oil leak from any seal associated with rear diff/carrier/axle

I dont think it matters whether you use standard or sythn gear oil
rather that you change it every 15k miles as toyota specs

furthermore, if yo plan to keep a tacoma for 100-150k miles
you could probably get away with never changing it
but if you want to get into high mileage with a taco its best to keep up on this
critical powertrain point

 

I follow the guidelines from Toyota, every 30k miles. 174k on it with zero issues using the cheapest fluid i can find.

 

Irony. I see it.

I won’t bother with any response save for: at Toyota’s recommended interval (30k), you could run whatever you wanted without undue wear. Your outlier experience does not mean that synthetics aren’t perfectly acceptable for Toyota diffs - the dozens of high mileage examples of that (within this thread and throughout the site) are a larger sample size than your n=1.

Also, one company recommending a single brand should be cause for a rationale observer to pause and take note. Could they have ulterior motives? Perhaps a monetary agreement? It’s a small company, maybe the owner is a dirt track fan and appreciates what Lucas oil does for that scene (I know I do). Any one of a million possibilities other than “synthetics make Toyota diffs leak.”

Relax dude.

 

When I changed my rear, front, transfer, and manual transmission oil I never took it out for a drive right before changing it. Does it matter if I didn't do this?

 

It will drain better when warm... but you are fine. Try it next time and see if it helps.

 

Thanks, that was my thinking too and will take your advice next time.