Transmission Fluid Pump?

[weene27]

It seems that the transmission issues on the RX300 stem from dirty fluid or poor circulation...is there a fluid pump that handles this? Is it possible that these units have intermittent issues causing long term damage?

[monarch]

No one has reported a RX transmission failing before the 30,000 mile mark - when the fluid was still in good condition. Therefore to keep the fluid in good condition at all times it makes sense to drain and refill the 4.9 quarts in the fluid pan and differential every 15,000 miles.

[mikey00]

It seems that the transmission issues on the RX300 stem from dirty fluid or poor circulation...is there a fluid pump that handles this? Is it possible that these units have intermittent issues causing long term damage?

I suspect that it is not dirty fluid causing the problem. The real problem is in the design and certain parts wearing causing the dirty fluid. Of course this is just speculation on my part and I don't know if we will ever find the correct answer. I am playing it safe with a 15K drain and fill schedule.

[wwest]

The fluid is not only somehow getting contaminated it is also getting burned via overheating somehow.

I have no problem with the contamination, that's simply a matter of the various clutch surfaces wearing and the resulting debris contaminating the fluid. Contamination via wear is something that normally happens over a much longer period, say in excess of 100,000 miles.

ATF contamination in these transaxles is happening at a much higher rate as a result of the AGL, Aggressive Shift Logic, and other new shifting options adopted by Toyota early in this century. You can read about all three of the new "shift" methods via "Googling" for "Sierra Reseach". IMMHO the adoption of these methods resulted in a dramatically higher number of shifts per mile and that, of course, is causing the higher wear rate on the clutches' frictional surface.

The RX300's ATF is overheating both as a result of the higher shifting loads and the heating of the ATF via heat transfer into the diff'l from the adjacent viscous clutch assembly in the attached PTO.

Toyota and Lexus eliminated the problem of RX300 premature transaxle failures in the RX330 by eliminating the viscous clutch entirely and by adopting DBW, e-throttle, to significantly reduce the wear rate of the transaxle's frictional clutch surfaces.

Just as Toyota has stated publically, the RX330's DBW is being used to "protect the drive train".

I'd be willing to bet that since the RX350 again has a viscous clutch within the PTO the diff'l "sump" has been redesigned to allow the ATF to circulate from the diff'l into the transaxle case and thereby to the ATF cooling system more readily.

[jgr7]

I was thinking about this burnt dirty trans fluid thing again and wondered what everyone thinks about changing the fluid in the differential only at the same time we change the engine oil and filter. I mean if the oil exchange in the differential is not very good removing the bad fluid every time the engine oil is changed it might remove the worst of the fluid and it will only cost approx 1 Qt of fluid and a few min more time.

Jeff

[monarch]

I don't have an RX, but from what I have heard, the fluid in the transmission oil pan and differential will both stay pretty pinkish if both are drained and refilled every 15,000 miles. I also have heard that although the differential and oil pan have separate drain plugs, they both share a common fill point (the transmission dip stick opening).If all this is true, then I don't think there would be any point in draining the differential alone more frequently.

[artbuc]

I don't have an RX, but from what I have heard, the fluid in the transmission oil pan and differential will both stay pretty pinkish if both are drained and refilled every 15,000 miles. I also have heard that although the differential and oil pan have separate drain plugs, they both share a common fill point (the transmission dip stick opening).If all this is true, then I don't think there would be any point in draining the differential alone more frequently.

With all due respect Monarch, my experience suggests you may be wrong on this one. On my last drain and fill, ATF from the differential was noticeably degraded while ATF from the sump looked like new. Sharing a common fill point doesn't necessarily have anything to do with the degree of mixing. I have never disassembled the trans and don't have any engineering drawings so I do not know if the fluid is mixing or not. I can just tell you what happened to me. My RX has 62k and I have done a drain/refill every 15k and a couple of times did multiple drain/refills which replaced over 90% of the ATF. I plan to drop the differential ATF only after 10k miles to check its condition.

[monarch]

On my last drain and fill, ATF from the differential was noticeably degraded while ATF from the sump looked like new. Sharing a common fill point doesn't necessarily have anything to do with the degree of mixing.

artbuc, I agree you could be right and if so then you and jgr7 may be one your way to learning how to obtain longer life from the AWD Rx transmission; i.e. drain the 1.x quart out of the differential sufficiently often to keep the fluid looking fresh.

I know the 1984-2001 2WD, 3 speed automatic Toyota Corollas have separate drain and fill plugs for the transmission oil pan and differential because the fluids in the two units do not mix and owners who have neglected draining the differential have ended up with premature transmission failure.

I am unsure about the degree and rate of mixing that occurs in the RX transmission and differential. wwest's anecdotal experiece where the fluid on his tranny dipstick looked clean one day and then suddenly became darkened the next time he checked it might suggest the fluid in the differential became overheated from a specific driving event and then gradually mixed with the rest of the transmission fluid, causing it to darken as well.