Rear Differential & Transfer Case

[Lexmex]

After getting my Royal Purple 75W90 Synthetic Gear Oil yesterday, my uncle, cousin and I went ahead and changed out the fluid in the rear differential and the transfer case. We later did the front differential and transmission, which I will talk about in a separate thread.

Royal Purple won the who can import to Mexico sweepstakes, but I also tried to get Liqui Moly and Mobil 1 gear oils, but no dice.

2 bottles of the 1 quart (.946 liters) is all you need to do both the rear differential and transfer case.

This was one disgusting job.

I wanted to add that I have 107K miles on my RX.

Note: over the years I have done this a few times. One may want to take a look on page 10 where I do it again as it might be more helpful.

[Lexmex]

Let's start with the rear differential.

I would highly recommend you start off by opening up the fill plug, which is located just to the left of the passenger side, rear right wheel.

The service manual does a decent job showing the locations.

[Lexmex]

Another picture of the same area taken a little further back.

[Lexmex]

This is where the fluid exits.

[Lexmex]

This is another shot of the area. Antonio Jr. and I tried different hex wrenches until we got the right one as in our shop everything is scattered all over the place.

[Lexmex]

Here comes the old fluid. This fluid was a lot cleaner than the transfer case fluid we will see later.

[Lexmex]

This is the transfer case fluid and notice it has kept its color after a year (this was Royal Purple 75W90 MaxGear). The rear differential was the same in its consistency. The overpowering smell was slightly there, and it still didn't wear off my hand until this evening.

[thomas1]

I too, noticed very little change on the rear differential oil on my second change. The Front oil was dirty, but I cant smell well, so I have to pass on that observation. I just replaced the Mobil 1 synthetic with Royal Purple. Thanks Lexmex for the great pictures.

[1SICKLEX]

Fantastic write up!! Thanks for sharing

[chenxingha]

Thanks for the photos, directions and discussions.

I changed gear oil for the rear differential box on my wife's 2000 RX300. The drain plug's magnetic extenssion has some deposits and the old oil is of brown. An hour ago, I replaced the gear oil with Coastal 80W/90 that my local Toyota dealer uses.

Now with front. I have two questions. Thanks to the photos by Lexmex I was able to locate the filler and drain plugs at the fron passenger side. While studying how to get the ranch and my hands around, I noticed that there is another plug on the "bigger box" at the driver side (use the exhaust pipe as a divider). It seems to be a drain plug, seems to be the same type and size as the two on the rear differential box. This bigger box is right next behind the transmission oil pan. This plug is facing the center towards the exhaust pipe. It seems to be the same type and size as the drain plug on the transmission oil pan. My first question is: what is this plug for and if it is a drain plug, where is the companion filler plug? (What is this bigger box for anyways?)

My second question is perhaps of elementary nature to many: I read the posts of this thread and noticed the use of "transfer case" and "differential case" . What are the differences (or are they the same thing?)?

Thanks.

[Lexmex]

Tht would probably be the front differential, though some also call it a transfer case. Thing to remember about that one is that it drains ATF. You fill it through the tranny dipstick and eventually it will trickle down to this area and also where the tranny pan is. ALWAYS drain this (about .5 liters of ATF in there) along with the tranny drain plug when doing an ATF drain and flush. Is where the wrench is in this case, the are you were referring to?

Differential and transfer case are interchangeable terms.

[Meetya]

Guys, I have been watching this thread and your progress.
For your future reference, here is a (rare?) picture of the transfer case from above (engine is removed).

[Meetya]

Originally Posted by Lexmex

Differential and transfer case are interchangeable terms.

Not quite. Although they perform very similar functions they are not the same unit. "A transfer case is a part of a four wheel drive system found in four wheel drive and all wheel drive vehicles. The transfer case is connected to the transmission and also to the front and rear axles by means of driveshafts."

Transfer case -- transfers torque between front and back.
Differential -- equalizes torque between left and right axles.
FWD RX (uses U140E) does not have a transfer case, just the front differential.

[Lexmex]

Originally Posted by Meetya

Not quite. Although they perform very similar functions they are not the same unit. "A transfer case is a part of a four wheel drive system found in four wheel drive and all wheel drive vehicles. The transfer case is connected to the transmission and also to the front and rear axles by means of driveshafts."

Transfer case -- transfers torque between front and back.
Differential -- equalizes torque between left and right axles.
FWD RX (uses U140E) does not have a transfer case, just the front differential.

Actually when this came up, members on this forum were calling what I call the front differential the transfer case and vice-versa. That was the reason I was referring to interchangeable. We have a similar issue with O2 and A/F sensors, and officially, as far as Lexus, the A/F sensors are before the main cat and the O2 sensor is after.

[Meetya]

These are official Lexus specs. Both (!) differentials and the transfer case use 75W90.