Ask a Mechanic: The Tricky Reality of Some Transmissions

Dear Ask a Mechanic,

I bought my Toyota RAV4 new and it now has 180,000 kilometres. A few years ago I took it to the dealership to have the transmission flushed as part of its regular maintenance. Shortly after, the car began to jerk and hesitate when shifting into third gear.

The dealership recalibrated it and it worked fine for three weeks, but the problem returned. I then took it to a transmission shop, where they dropped the transmission pan and found nothing wrong. Afterwards, a second recalibration was done, and the vehicle ran perfectly again for five months.

Now the problem is back and a third recalibration did nothing to fix the problem. If I accelerate slowly or quickly, it doesn’t hesitate to shift into third gear. But he hesitates if I accelerate “normally”. I have been told that possible fixes include replacing the valve body, replacing the third shift solenoid, or replacing the transmission control module. Have you encountered this problem before? — Troubled transmission

I’ve seen something as simple as an all-purpose transmission fluid cause shifting issues in vehicles after they’ve been serviced. I don’t believe the dealer you originally took your RAV to would have used anything other than genuine Toyota approved fluid, I only mention this to illustrate how sensitive modern transmissions can be.

Although most auto service technicians (including me) service and repair certain parts of an automatic transmission, diagnosing and rebuilding them is a specialty. I raised your question with transmission service technician Eric Vandepol, who has 30 years of experience in the field.

Although the reader doesn’t mention the year of their vehicle, Vandepol said first-generation RAV4s, those from 2012 and earlier, are among the Toyota models known for engine control module faults. In these models, the module handles transmission shift control and may or may not be able to recognize and report a problem with the system. The reader does not mention if any error codes were reported.

Vandepol said the valve body would need to be removed to perform tests on it, but that will only prove if it is bad. It can also test well when the vehicle is not running and cold, but act when in use. He said the same goes for the solenoids, but these should trigger an error code if they fail.

Given the costs involved in fixing the problem, Vandepol said he was hesitant to say the engine control module was definitely the problem without inspecting the vehicle himself.

Ask a Mechanic is written by Brian Early, a Red Seal Certified Automotive Technician. You can send your questions to [email protected] These answers are for informational purposes only. Please consult a certified mechanic before performing any work on your vehicle.

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