stonedboot

I have 2012 Rx350 which has 136,000 miles on it. It shows high transmission fluid temperature when I drive it for 85-90 mph. It goes away when I reduce the speed.
I took it to the dealer and they said the transmission need to be replaced but every test they conducted showed no codes or anomaly and they suspect it might have transmission slipping from gear 3 and above. The car runs smooth and well on 70 mph and below.

Does anyone had this problem before? Is replacing the transmission only solution? What should I do?

salimshah

Hmm. I would visit another shop/dealership as at that speed the torque converter should lock up .. I assume you are driving at constant speed and not speeding up and slowing down.
On my own I would examine air flow over the cooler/radiator.
Did they check the fluid level .. specially if it was replaced.

Salim

stonedboot

CONFIRMED WITH MONGOOSE NO
CODES WERE SET IN ENGINE CONTROL UNIT, TRANSMISSION CONTROL
UNIT OR ANY OTHER SYSTEM INDICATING ISSUES WITH ANY SYSTEM
IN TRANSMISSION OPERATION. ROAD TESTED ON TOLL ROAD FOR TEN
MINUTES AT POSTED SPEED LIMIT OF 75 MILES PER HOUR. DURING
ROAD TEST NO WARNING INDICATORS ILLUMINATED AND NO HIGH
TRANSMISSION FLUID TEMPERATURE WARNING ILLUMINATED ON
INSTRUMENT CLUSTER. OBSERVED AT LIGHT THROTTLE TRANSMISSION
GEAR CHANGES THREE AND UP WOULD SLIP DURING TORQUE CONVERTER
ENGAGEMENT. NOTICED DEPENDING ON LIGHT THROTTLE ENGINE
ROUNDS PER MINUTES WOULD FLARE UP INDICATING SLIPPAGE. ROAD
TESTED AT MORE THAN LIGHT THROTTLE UP TO HALF THROTTLE AND
OBSERVED NO TRANSMISSION SLIPPAGE DUE TO TORQUE CONVERTER
WAS NOT ENGAGING DURING MODERATE THROTTLE. NEED TO REPLACE
THE TRANSMISSION AND TORQUE CONVERTER BEFORE FURTHER
DIAGNOSIS. SUSPECT FLUID SHEAR FROM TORQUE CONVERTER
SLIPPAGE CAUSING HIGHER TRANSMISSION FLUID TEMPERATURE.

They said this.

Oro

When was the last transmission service, and how much fluid was replaced? Any additives used? WS fluid, or another type?

LeX2K

^^ this

spend $200-$300 and get the fluid replaced if it doesn't help then you will likely need a new transmission.

carguy75

My 2015 RX350 AWD transmission did that when I first bought it and took in on the highways at high speeds above 80mph every-time after about a hour of driving. The message went away when I slowed down to about 60 mph. I checked the transmission fluid level and noticed that it was overfilled by 2quarts or so. Too much fluid can cause the transmission to overheat due to the fluid foaming up and not flowing well.

I solved the problem by draining out the excess transmission fluid and topping it off at the proper level. The transmission has been running perfectly so far about 2 years later after the fluid level correction without the transmission overheating message on the same stretch of highway at 80mph+ speeds for long drives. I used Valvoline Max Life fluid as the replacement fluid during my top off.

I would check your transmission fluid level first and then go from there. The previous owners or repair shops can overfill the transmission during a fluid change sometimes before you buy it used.

Sometimes I rather not buy a used car that was not serviced by the dealer because of mistakes that can happen by DIY owners or by some general mechanics that do not know how to service the car properly.

carguy75

I forgot to add that my transmission also had an odd low speed slip at around 20mph as well before I adjusted the fluid level. If your transmission always seems to slip at 20mph then it could be the same problem I had with an overfilled transmission for sure.

The low speed slip went away when I adjusted the fluid level as well 2 years ago.