I have an issue where around 40 mph, coasting, then light gas pressure applied, I feel a shudder like going over a rumble strip. It happens 1 out of 7-8 times I do it. From other posts, it sounds to me like this is torque converter shudder. If I turn off O/D it NEVER happens. I assume because the torque converter does not lock up when O/D is off?? Is that correct? But my question is, can that be caused by something other than a bad torque converter? I had my torque converter replaced a year ago, since the vehicle was lunging when stopping at a light, and slipping when starting again. That seemed to be solved. Now this new issue has developed. Aside from a bad torque converter, what other issues could cause the torque converter to shudder like this? I’d appreciate any advice.
I had bad TCC (torque converter clutch) shudder in a camper van I had just bought. Changing the trans fluid and filter solved it.
Try a fluid and filter change first. If that doesn’t solve it, then you can suspect the TCC itself.
Sounds like torque converter shudder to me too. I would drain the transmission and the torque converter (I believe it has a drain plug, but not sure), and refill the system with genuine MerconV fluid–not some store brand that claims to meet all specs. Lubegard also makes an additive called Shudderfixx to address this problem.
Thanks for the feedback… could it be caused by some other mechanical failure? Other than torque converter or fluid? Reason I am asking, is that my mechanic has told me it is the mechantronic unit… but I am not interested in a fishing expedition… that is a lot to spend if it is not the problem.
I am trying to understand if the valve body (mechantronic) has any failure condition that could possibly cause torque converter clutch shudder. It appears to me the clutch is completely controlled by a solenoid and the computer. And the only possible causes are clutch itself, dirty fluid, or solenoid (not sure if solenoid problem would be intermittent like this or complete failure). Is that accurate or could the valve body be causing the issue?
I’m not the expert, but when I had the TCC shudder problem I was told by the experts that if a fluid change didn’t help, it would be the clutch or solenoid, not the valve body.
And as asemaster said, if a fluid/filter change doesn’t help, you can try the Shudderfixx additive.
Does the valve body only control shifting inside the transmission? What is the connection between the torque converted and the transmission. I mean, I know it is mounted on the shaft coming out of the transmission, and I assume fluid transfers between transmission and torque converter also? but is all torque converter operation controlled entirely within itself? where does the torque converter clutch solenoid sit?
The torque converter is a viscous coupling between the engine and the tranny. The OD is when the torque converter locks up and engine rpm equal tranny rpm.
I am assuming you have the 4.6 liter V8 engine, 2W drive, and the 5R55S transmission
The valve body in the transmission and dedicated solenoids control the function of the lock up torque converter. The Torque Converter Clutch solenoid causes a shuttle valve in the valve body to reroute fluid flow so the torque converter will start locking up. There is a second solenoid that controls the pressure against the lock up piston to ease the engagement and hopefully keep the clutch from shuddering.
The fluid flow when the TC is unlocked is from the center passage of the input shaft to behind the lock up piston to the stator support shaft hence to the transmission cooler. When the TCC solenoid is commanded to swtich the shuttle valve, the fluid flow is from the stator support shaft into the TC hence against the lockup piston. The flow out of the TC is via the center passage of the input shaft hence to the cooler. The fluid pressure for the fluid intering via the stator support shaft is controled by a Pulse Width Modulating solenoid that adjust the TCC apply pressure at the command of the mechantronic controler.
There is a diagnostic procedure to check the realized pressure against the commanded pressure. This is done with a scan tool and a pressure gauge. My information does not show which of the 3 pressure solenoids controls the lock up pressure.
I think the torque converter will lock up in all the of higher ratios i.e. 3rd, 4th, and 5th. One way to descern if you have lock up clutch shudder is to lightly touch the brake pedal to the point where the brake lights come ON. If the TC is shuddering it should stop while the pedal is depressed. You also might have a driveablity problem where engine combustion problems show up as a drive line shudder.
Hope this helps. Keep us in the loop with what you find.
Researcher… thank you for the very detailed description! That helps me a lot! From what you said, I understand now that there are valves in the transmission that do affect the clutch lockup. I think I have the 6R60 transmission, but I could be wrong.
So, since the dealer is saying they “did road test with scan tool monitoring transmission data, and found fault with mechantronics unit”… is it standard dealer practice to swap out the entire valve body, or can the valves related to clutch operation be replaced much cheaper? Would it also be prudent for me to try a fluid flush and shudderfix first before spending $ on any physical repairs?
I have a BT1 scan OBD module… with iPhone app… what parameters are they specifically monitoring to see the TCC and valve body operation?
Researcher - is right, the torque converter clutch should lockup in the other higher gears.