Front & Rear Differential Factory Fill Low

Just changed the fluid on the front and rear differential of my 2019 TRD Pro with ~12K miles. Measured the drained fluid from both differentials Rear was .5 -.6 quart low The front was low .3 - .4 quart low. Put in Redline 75W85. The truck seems to drive smoother and the slight wine noise in the 50s when feathering the throttle is mostly gone. The front fill was approximately 20% low and the rear 1/8 low. Is Toyota squeezing $'s and filling them on the low side of specifications?

 

You're not alone I found my rear diff was pretty low when I dumped it around 850 to replace with Redline.

 

Did you change your front as well? The front only holds 1.6 quart and it was .4 low

 

When you drain your diffs there is still gear oil inside, it will not be the dry measurement when refilling. Don’t ask why I know this. I put 4 in the rear and 1 in the front. But I have a locker in both. If you over fill it it will leak through the breather.

 

I’ve toured the factory. They use an auto fill system, guy filling the diffs just puts a nozzle in, it puts in the measured amount, so if they unit is off a bit I could see why they’re low on fluid.

 

The front one I didn't measure, but I did change

 

People have been suggesting underfilled diffs for years now though. Toyota builds 200,000 of these things a year. I'm pretty sure if there were a calibration problem with the fluid metering machines they would have fixed it by now.

That said, these machines do have tolerances, and as such, some trucks are getting slightly less fluid than others, but all of the trucks are in spec.

 

Both of my differentials were under-filled. Front by .5qt and rear by .7qt. I measured exactly how much came out and exactly how much went in to the fill line. I used redline

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

75w-90. 75w-80 is too thin for my taste and even for Toyota's (squeeze every MPG) taste, which specs it at 75w-85.

 

Honestly it makes sense the rear diff on the TRD OR is larger than the other ones. If they are filling them all the same and not adjusting the quantity dispensed then the issue arises.

Mine was 1/2 a quart low as well.

 

You can blame the dealership you bought it from as all Toyota vehicles go thru a new vehicle check list prior to the owner taking possession. Topping off all fluids is on that list.

 

I'm kinda surprised that there is a noticeable \ detectable difference just changing the differentials fluid. Drivetrain is abit quieter. Not that it wasn't quiet, it is. Had a little bit of a whine that started around 7K in the 50s on gas feathering, even that is all but gone.

 

Guys, draining your diff is NOT an accurate way of measuring how much oil was filled at the factory.

The entire inside of the housing, all faces of the gear, all faces of the pinion, the axels, and everything else in the diff is covered in oil even after you drain it. There is also a small amount pooled at the bottom of the diff, opposite of the drain plug and around it. All of that certainly adds up. Point is, you’ll never get every drop out.

I rely on the age old method of checking the fill hole; if it’s not right up to the fill plug while on level ground, top it off. Mine was about 1/2” low.

 

You'll never get the full amount of oil out when you drain it... plenty gets left behind in the axle housing and stuck to the gears.

If you want to know if it's full or low, simply remove the fill plug. The diffs, tcase and (manual) transmissions get filled with gear oil to the point where the fluid will run out when you take out the fill plug...if you remove it and nothing comes out, you're low. Draining it and measuring what comes out versus how much is supposed to be in there is not accurate at all

 

Checking the differential, transfer case or transmission fluid levels are NOT on the dealer make ready check list generated by Toyota.

 

Better yet, just drive the truck and stop worrying about it.

Change out the oil every 15k miles, per the owner's manual, and that's that.

 

Differential fluid levels are not on that list. They are inspected visually for leaks. Dealers are not instructed to remove any plugs to check the fluid level.

The acceptable range for the amount of fluid in the differential is pretty large, and a lot stays in various places after driving the vehicle. You will almost always put more in than you drain out on the first fluid replacement, and possibly on subsequent services as well.

Jeff

 

As others have said, it’s not that big of a deal. Your diff isn’t going to grenade itself being .5 of a quart “low”. Drive the truck, change the fluids at the recommended interval, and continue on. Toyota knows what they’re doing, otherwise you’d see a recall or a TSB.

 

This was a pretty common problem with the 2016 and 2017 trucks. It took just over half a quart in the rear diff to make fluid spill out from the fill plug. I am hoping that this was corrected for subsequent models.

Was pretty standard on earlier models to check. Look up the howling rear diff thread, the leaking rear diff thread, etc.

 

^^Agreed. I would add to this by saying that I always check these fluids after driving around the block, and with the truck on level ground (or on a drive-on hoist, never a 2-post hoist though)

PS. Both my front and rear diff fluid was low from the factory. Transfer case was perfect.

 

It's actually rather simple, for example, you remove 1.1qt and fill back in 1.6qt (front diff) to the fill line, which makes it .5qt low. I believe Toyota lists "wet fill" in the manual. "Dry fill" is always more, which makes it irrelevant how much was filled at the factory, it was still .5qt low.