Fern

O.K. folks gotta get it right!


The confusion comes when the manual says the differential takes gear oil and the experts on the forum say to put T-IV in the front differential.

My question is if the drain plug that LEXMEX shows as the front differential is the horizontal drain immediately behind the trani plug, and if it takes T-IV, and if it refills through the dipstick, then why won't draining the trani and refilling the trani be sufficient?

Why would front differential take T-IV while the rear take gear oil? And shouldn't circulating T-IV in the trani eventually mix with whats in the front differential (if it fills through the same spot)?

Anyone confused yet?

Just doesn't seam clear to me and I know there are other members in the same boat

Lexmex

The problem that I encountered on OTHER vehicles was that the Type-IV fluid that winds up in the front differential area is shared with the that in thet transmission does not circulate as well. I sort of remember at least 1 or 2 posts in the forum of how the fluid that came out of the front differential in color slightly from what came out of the drain plug.

The rear differential on transfer case on AWDs use gear oil and are not connected fluid wise to the front differential and tranny.

Tammy

There is a front and rear differential

The front contains and shares the Type IV with the transmission. It has a separate drain plug. This is referred to as a transaxle, rather than a front differential and transmission combination unit. They share the same aluminum case.

There are two different transaxles installed on the RX300, one for the all wheel drive (U140F) and one for the front wheel drive equipped vehicles(U140E).

On the AWD models, off the right side of this front differential is a transfer case; in line with the right axle drive shaft. This transfer case drives the propeller shaft to the rear wheels, through the rear differential. Both these units are filled with 70W-90 GL-5 gear oil.

The front wheel drive transaxles use no gear oil anywhere.

With the previous pictures provided, I hope this clears up the confusion.

TunedRX300

When in doubt, just pour in the same type of fluid you drained out.
No matter what name you call it, it is GL-5 gear oil that goes in and out of 15/16 drain/fill nuts; T-IV goes out of 10mm drain plugs.

Tammy

The rear differential uses 10mm hex plugs, like the transmission.

Fern

So when my owners manual says for the AWD trani drain and fill to use 3.9 litres (it includes what is being drained out of the front differential)????

Just checking since I drained and filled this weekend past and did not drain the front differential...

Did I overfill the trani by the amount of the front differential that wasn't drained.?

Lexmex

Good question.

The last time I did it and pulled the front differential plug, I noticed I had to add .5 liters more than when I previously just drained the tranny pan.

The best way to do this is to first pull the tranny plug and let it drain all the way out...then pull the front differential plug and measure (I did it with a used Mobil 1 oil bottle).

cerritos

For a two wheel drive RX, it would be a disaster if the front transaxle is drained but not filled. Yes they say that by filling through the transmission dipstick filler tube, fluid will be flowing to the front transaxle also.

I guess it would be a safe guard by just opening up the front transaxle drain again after it was filled through the tranny dipstick tube to make sure the fluid did indeed fill it up.

Although theoretically speaking, by opening up the transaxle drain again, it could drain the whole tranny and transaxle fluid completely since they are connected and share the same fluid.

Lexmex

It will fill if you go through the dipstick, but I would wait at least 1 minute or so that it all trickles down into the front differential.

Tell you what...when I do my next ATF drain and fill in December (I do it 3 times), I will take a short video of the experiment where after we drain everything, I pour a little of the old fluid down the dipstick and we can watch it exit the front differential. We can see how many seconds it takes.

salimshah

This is all conjecture .....

Transmission fluid ... other than lubricating and providing flexible coupling (via torque converter) circulates the unwanted wear. The unwanted wear is either metalic (magnetic and non magnetic) and powdery stuff.

As time goes bye, the fluid detiorates due to temprature (slip ... energy tranformed in to heat).

Be prepared ... getting into controvertial stuff ....

The unwanted stuff is either sedimantary ... which settles in the pan over time or non-sedimantary which keeps circulating ( as long as it can pass through the screen/filter).

Ppl with paper-like filter traps more of the junk but over time have a potential problem of starving lubrication. [Problem if the filter is not replaced at a reasonable frequency. Also filter will allow yet smaller particles to go through]

Ppl with screen, keep sending the the non-sedimantary junk through out the transmission. The normal Lexus maintainance guidelines are based on thermal breakdown and sediment drain of trans fluid. The porcupines in the pan keep growing and bottom sludge (imovable) stays at the bottom. Nothing wrong with that as long as this junk never gets into circulation.

2 Drain: Each drain spot is in a different chamber, with its own lowest point. So double drain would cause more fluid to be replaced.

Salim

TunedRX300

Tammy
Thanks for the note but drain plugs under discussion/confusion are exclusively from the front.
Salih,
Good summary. Just one note that ATF also is a coolant, transfer heat away and disappates it in the cooler. Better fluid will be able to withstand higher temperature.
If one needs to find out Toyota T-IV, just reference to the published spec of Mobil ATF 3309's. BTW, ever wonder why Mobil 3309 has the same shaped bottle as Toyota T-IV? My take is that Mobil can use the same assembly line for different branded products, just change the label and of course charge different price.