Rx300 Transaxle Failures

[wwest]

I have noticed a trend indicating that many posters believe that the premature transaxle failures some (many?)(a few?) are having in the RX300 only pertains to the AWD version.

With no opinion one way or another myself I did get to thinking about just what might be different in the AWD version that might cause the transaxle itself to fail.

Last winter my daughter and family went snow skiing in their AWD Chrysler T&C. They had a full set of summer wheels/tires and winter wheels/tires. The winter tires were on the OEM wheels and the smmmer tires, Bridgestone Turanzas were on 16" plus size wheels, correctly sized.

But my son-in-law only put the winter tires on the front since that would save time and the snow chains would fit.

They got about 50 miles before the PTO section of the transaxle failed. Apparently the slightly disparate tire sizes front vs rear had caused a severe overheating of the PTO. Given my own experience with the RX300 viscous clutch always remaining so flaccid it cannot drive the rear wheels it was initially hard for me to believe that was what had happened. The Chrysler VC had worked so well that the drive train had overheated and failed.

Some of you may remember that when I first purchased my 2001 AWD RX300 I quickly became suspicious that the rear wheels were not being driven. I did some shade tree testing that determined to my our personal satisfaction that the rear wheels were not recieving any substantial level of engine torque.

But several posters here questioned the validity of my shade tree testing so I took the RX to be tested on a 4 wheel dynamometer. That testing verified that the engine torque to the rear was initially about 10% and only after minutes of disparate F/R loading did the ratio rise to something like 75/25 F/R.

Today, just moments ago, I repeated my shade tree test procedure. With all four wheels well off the ground, engine running and in drive I first verified at idle that I could stop any one wheel from rotating with light hand pressure. Then I verified that I could stop both rear wheels without affecting the rotation rate of the front.

Next I blocked each rear wheel with a piece of light pine 1x2". Just a light touch of the gas pedal resulted in an immediate breakage of the 1x2".

That is NOT what happened 4 years and 50,000 miles ago. At ~2000 RPM engine speed all I could get from the 1x2's at the rear was some creaking.

My guess, now, is that the reason my ATF looked and smelled burnt at 40,000 miles is because the viscous fluid has congealed for some reason and now the center diff'l is always "locked" by some very high percentage.

That would undoubtedly result overheating of the PTO lubrication and most probably the ATF just behind the shared "wall".

Is this why the RX300 transaxles are failing prematurely??

[LexKid630]

What do you think causes the center diff'l to lock more over time?

Any specific driving habits?

[wwest]

My best guess would be that the viscous fluid in the clutch/coupling is, for want of a better word, congealing, over time, distance, and heat cycling.

[LexKid630]

My best guess would be that the viscous fluid in the clutch/coupling is, for want of a better word, congealing, over time, distance, and heat cycling.

←

So the best anyone can do is replace the fluid often so it stays thin?

[lenore]

I am confused, are you talking about the front differential that takes 80-90 weight fluid, or are you talking about the transaxel off the transmisssion that takes toyota TIV that shares its fluid with the transmission.?

[wwest]

The viscous clutch/coupling is mounted in the PTO section of the transaxle. The VC is hermetically sealed and contains a specially formulated viscous fluid.

It is the viscous fluid that I suspect is congealing. The only fix would be to replace the VC, viscous clutch itself.

[lenore]

Oh, great, How expensive is that?

[lenore]

I thought of one more variable, Some of the AWD had limited slip as an option on the drives.

[wwest]

It doesn't seem likely that the LSD at the rear diff'l could result in a transaxle failure. Besides which it wasn't available as of the 2001 model when Trac took over that responsibility.