A few socket and wrench sizes in question....
15/16 = 24mm

Upper fill plug - Transfer case - 15/16 socket with a 6 inch extension (at least)
Lower drain plug - Transfer case - 15/16 Open end wrench

Upper fill plug - Rear differential - 10 mm allen hex socket - 3/8 or 1/2 inch drive with 6 inch extension
Lower drain plug - Rear differential - 10 mm allen hex socket - 3/8 or 1/2 inch drive

Both of the units are cast iron where the plugs screw in. A 10mm "L" shaped allen wrench won't quite do the job. With a socket 10mm allen, you can torque the plug correctly. I torqued the plugs to 40 Ft Lbs.
Expect to find 18 mm inside diameter steel compression seals under the plug heads. They can be reused, but replacements are recommended when disturbed. I used Toyota replacements rather than Lexus. It's a standard seal.

 

My cousin is one strong dude. He is bigger than a lot of offensive lineman in the NFL. Once he got the tools, his fists did all of the work, but for the rest of us...that is another story.

I don't know prior to 40K miles what if any was done with regard to the differental and transfer case fluids (will check with Lexus next time I am in the U.S.), but going over my invoice sheets on the last services I had with Lexus (2004 was the last time), I don't see anything mentioned.

 

I found this shot left on my camera chip of Antonio taking off the drain plug on the transfer case.

 

Great write up Lexmex. It was very detailed and the pictures help very much...

 

I was planning on doing this again near the end of the year or come next April (1 year later), but since my RX sits at home during the week, may wait until I get about 20K miles on this fluid. I wanted to see the buildup and the color, smell for future reference.

By far, the more important thing to do is drain the tranny pan and front differential, clean out the pan and change the filter and gasket.

That smell from the transfer case still sticks out in my mind even a few months later.

 

I did the rear differential oil change today. I filled about 1 qt of gear oil in before it started to spill, no problem there. But later I found out there was way more than 1 qt (maybe 1.3 or 1.4 qt, my best guess) of oil that was drained out of the rear differential. That makes me wonder maybe more than 1 qt of gear oil was filled in when the car was new from the factory?

 

I'll have to check what comes out in terms of volume next time on mine. I am trying to think of chemical properties in terms of shearing over time that would cause an expansion of molecules that would result in more volume after miles of being under pressure.

Keep in mind also for example that offhand I remember that the dry fill for the motor oil for our RX300s is higher than the amount needed for changing out the oil w/filter.

 

Well, it is has been about a year since I did this procedure and as I promised last time, I would check out the fluid after a year. 13,000 miles went by.

The two things of interest after changing both the transfer case and the rear differential, was this slight accumulation on the the drain plug of the transfer case. There was SURPRISINGLY no accumulation on the rear differential drain plug (zero...zilch...nada) this time.

 

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.

 

Hmm...13K piled on the gear and nothing came off. Anything on the front drain plug?
wwest tested for the AWD, both with Dyno and his own garage test of "jacking up all four and break a lumber". His finding is AWD for the RX is a 90-95% FWD, rear wheels are dragged along.
It is very hard to believe that if rear axel is used to deliver power, some metal got to come off in 13K.

 

Only accumulation on the front was in the photo of that drain plug above.

My uncle was quite shocked at that on the rear, too, but he claimed he has seen 1 or 2 vehicles that had nothing on the rear plugs, depite having cruddy old fluid.

I believe wwest on that, I really don't feel that power coming off the rear, but the AWD does help get some excellent, no spin launches at the track.

 

Thanks, your finding is valuable. It is almost 2 years since I replaced both front and rear differentials with Mobil 1 75w90. Your finding supports wwest's tests that rear gear oil and axel did not get used up as much as front one.

 

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.

 

Fantastic write up!! Thanks for sharing

 

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.