Drive line shudder

Exploding Reliability Myth-part 2.

My 2017 SR5 developed a strange shudder at 48,000 miles. It felt like a washboard road. It occured driving in "D" with light acceleration and speeds 20 to 40 MPH.

The shudder lasted a couple of seconds and quickly shifting into "N" seemed to cancel the shudder.

My Toyota Dealer diagnosed a Torque Converter internal part failure (part1). After checking with Toyota, The TC was replaced under my Platinum Service Agreement.

The shudder returned within a few miles.

I starting my own research reading on line about Toyota's FlexLock Torque Converter lock up clutch issues and TSB's going back to 2007, across several models of vehicles.

After a few weeks the shudder was very repeatable and I went back to dealer. This next covered repair was a replaced transmission (part 2).

A lot of excellent information is in "transmissiondigest.com" which gives technical information and pics showing the tranny valve body Lock up relay and control valves.

I highly recommend a transmission fluid change before the 60 month/60,000 mile drive train warranty expiration.

Look for beige opaque tranny fluid, which is the TC lock up clutch excessively worn clutch material. A strong clue there is a problem.

Driving in 4S changes the FlexLock engagement and minimizes shudder of a defective FlexLock system.

It is a shame that a small relatively inexpensive component (probably outsourced) in the tranny valve body causes such a large and expensive vehicle repair.

I purchased the Platinum 7 year/100,000 mile S.A. in anticipation of electronic gadget failures of which the 4runners have too many. I used to believe in the 4runner Reliability Myth. This experience exploded that belief.
Hungryhawk