2015 RX 350 transmission slips when backing up
Thread Starter
3rd Gear
Joined: Jul 2025
Posts: 3
Likes: 0
2015 RX 350 transmission slips when backing up
135k miles U.S.
all scheduled maintenance has been done at the original selling Lexus dealer
i purchased 8 months ago and has been very good.
the transmission started to slip when backing up a slight incline.
The local Toyota dealer changed the fluid and set the level with their scan tool.
They recommend replacement.
any other suggestions?
all scheduled maintenance has been done at the original selling Lexus dealer
i purchased 8 months ago and has been very good.
the transmission started to slip when backing up a slight incline.
The local Toyota dealer changed the fluid and set the level with their scan tool.
They recommend replacement.
any other suggestions?
Instructor
Joined: Jul 2025
Posts: 1,052
Likes: 191
I have no help to offer but have a couple questions-
135k miles U.S.
all scheduled maintenance has been done at the original selling Lexus dealer
Do the Lexus service records show servicing the transmission during the 135k miles?
The local Toyota dealer changed the fluid and set the level with their scan tool.
Did they flush the entire system and replace with new fluid or was it a so-called drain and fill replacing just a couple quarts?
I recently purchased an RX350 that had also been serviced at Lexus since new. 107k miles no record of transmission service. Folks here have convinced me to begin drain and fill which is equivalent to replacing about two quarts of the entire system capacity which I believe is near nine quarts.
135k miles U.S.
all scheduled maintenance has been done at the original selling Lexus dealer
Do the Lexus service records show servicing the transmission during the 135k miles?
The local Toyota dealer changed the fluid and set the level with their scan tool.
Did they flush the entire system and replace with new fluid or was it a so-called drain and fill replacing just a couple quarts?
I recently purchased an RX350 that had also been serviced at Lexus since new. 107k miles no record of transmission service. Folks here have convinced me to begin drain and fill which is equivalent to replacing about two quarts of the entire system capacity which I believe is near nine quarts.
Last edited by ChattanoogaPhil; Jul 20, 2025 at 03:52 PM.
Instructor
Joined: Nov 2015
Posts: 1,070
Likes: 367
From: Atlanta, Georgia
No offense to the dealership service department, but they tend to recommend replacing an transmission that can be rebuilt at a transmission repair shop.
I would have an transmission repair shop inspect your transmission(tear-down) and then go from there. It may be an bad reverse gear clutch or an bad reverse solenoid in the valve body. You will not know until it get properly inspected with a tear-down. Anything else is just guessing to what may be the cause.
I would have an transmission repair shop inspect your transmission(tear-down) and then go from there. It may be an bad reverse gear clutch or an bad reverse solenoid in the valve body. You will not know until it get properly inspected with a tear-down. Anything else is just guessing to what may be the cause.
Pole Position
Joined: Dec 2013
Posts: 3,466
Likes: 920
From: wa
Backing up an incline will strain the transmission - good test. Reverse gear is tall so that’s why. This is not unexpected behavior if the transmission fluid has not been changed. Best-practices maintenance would have been to:
- Starting drain/fills around 60k miles,
- then doing one again every 30k going forward
Does not sound like that was done. It would likely have prevented this. It is unlikely you have any “hard parts” damaged, just worn fluid. Toyota WS is not a robust fluid so wears and shears quickly. If you want better performance in the future, an LV (low viscosity) synthetic fluid would be a better choice. A lot of use MaxLife and are happy with the performance increase it gives over WS.
- Starting drain/fills around 60k miles,
- then doing one again every 30k going forward
Does not sound like that was done. It would likely have prevented this. It is unlikely you have any “hard parts” damaged, just worn fluid. Toyota WS is not a robust fluid so wears and shears quickly. If you want better performance in the future, an LV (low viscosity) synthetic fluid would be a better choice. A lot of use MaxLife and are happy with the performance increase it gives over WS.
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