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

 

I experienced a shudder during a light throttle application the other day but figured it was just the road. I have heard of this issue before but some fixed it with a trans go kit or a IPT reworked valvebody.

 

That is exactly how my FlexLock issue started. First I thought it was the road surface. But over the next few weeks it happened more and more. Then it was occuring all the time☹️.

 

Thanks for the post and the info. Good info to have in the back of ones head, as it could avoid a wild goose chase for someone in the future. It’s a shame that happened, but glad you had coverage. I experienced a failed transmission in my favorite car ever (1999 Honda Accord bought new). Original tranny only lasted a bit over 100k miles, and I had that thing so built up in my head, it was a big disappointment. Nevermind coworkers with essentially new chryslers that were in for tranny work all the time lol. After the dealer replaced it with a reman, the Accord went on to live a full and useful life.

I had a 2006 Sienna with the five speed. I remember it developing a shift shudder into 5th, that only lasted a second. It had probably 80k miles on it, and I had never changed the fluid. Once I did it went away. I wonder if that 5speed and the 4runner tranny are similar.

Interesting about S4 changing the lockup to reduce the shudder. From your research, do you suppose that driving in S5 all the time would help preserve the transmission? Or do you think that’s just a bandaid? To tell you the truth, I almost always kept my Sienna in 4th all the time around town, only shifting into drive on the interstate. Same in my 8speed Highlander…I bump it into S5 around town, to defeat the ASS system, and to avoid the constant shifting. Not that it doesnt shift decisively (because it does), but I just don't like the idea of unnecessary shifting, even if it saves me a few cents at the pump.

I’ve usually driven the 4runner in D because it honestly feels just right most of the time, but I’ve wondered if I should restrict to 4 gears around town…

 

I posted a chart some time ago that showed D vs the S modes and which of the S modes do and don’t have the flex lock. Can’t seem to find it right now. If I recall correctly, it doesn’t happen in S4 but does in S5. The only difference in S5 vs D is that in D the trans is logging data to “learn” from.

I could be wrong here, so don’t quote me on that. Memory is failing in my old age.

 

I hope a Toyota master mechanic will add some experience to this thread. I only have internet reading to base my opinions.
Driving in 4S around town makes sense as it "might" reduce wear in the lock up clutch plates.
I found this interesting chart on line:

I think careful watching the tranny fluid is the best way to prevent excessive wear in tranny. FlexLock issues supposidly do not create ECM codes. The tranny valve body seems the source of FlexLock issues.

 

It’s not a mode, simply a replacement for having multiple gear locations. You still get lockup in the normal gears.

 

If the chart @4runningMan referenced, and the one @Hungryhawk posted applies to our transmissions, it appears S mode is a little more sophisticated than just a electric gear gate.

Interesting stuff, I’m gonna have to research this to get a better understanding of how lockup works. One thing I have noticed using a OBM-2 dongle/data logger thingy, is that the trans locks and unlocks in S mode. It would be nice to have that for a bit of engine braking, although I don't know if thats worse for an automatic than just having it lock and unlock. Assuming flex-lock is just a name for some sort of intelligent lock algorithm, but I should look that up too.

Now that this chart explains things, I’m going try S3 to see if
the trans stay locked on accel and decel.

 

I started driving around town in S4 mode, after note of temp difference between trans oil pan and converter. In D (and in 4S) temp of converter is higher and stays higher longer, than in 4S. As the speed limit everywhere in town less than 40MPH, I will try 3S and see what happened with temps. As I understand now, for transmission 3S is the healthiest mode for town driving, D is for steady highway, 4S on entering highway and passing acceleration.

 

I’ve wondered if the flex-lock in S4 deceleration (according to the chart) only engages in the case of automatic engine breaking (ie. when going down a hill). And perhaps it doesn’t routinely engage when just driving around town.

 

Ah didn’t see it and I’m surprised it changes anything. I could have sworn I got lockup in S4.

 

My understanding of FlexLock is it modulates the clutch lock up. So McSpazatron is correct. I think the purpose is to make drivability smooth, and allow very low RPM.
My understanding of the shudder is the modulation stops releasing properly and acts as a chatter braking force. This also provides support to the idea of excessive lock up clutch wear- hence the beige opaque fluid at 48 k miles - contaminated by clutch friction lining.
I notice 4S engine braking when I release the throttle pedal.

 

So the engine braking is entirely different than flex? Or are they acting in tandem and that’s why flex shows in the chart as “on” in deceleration?

 

good question. The way Im reading it is flex lockup means locked, (torque converter blades arent spinning). Which seems to mean that “off” it doesnt lock, and “operates” means that it is allowed to lock???

So…S5 allows the trans to lock in the most gears? And S4 prevents it from locking in any gear in accel? Hmmm.

 

Those questions have been on my mind and unanswered for the last five years lol.

 

My drive this morning seems to show S5 locks the torque converter very quickly when you’re at light throttle, and it locks fairly quickly. It also holds locked under increasing throttle longer than in D or S4. Using Car Scanner app to see lockup, since its very hard to tell otherwise.