Quote:
Originally Posted by OzzieSS
Here's a thought.... I bought one of the those Range OBD dongle thingys that prevents AFM from kicking in. I plugged it in and I've been driving now for four days. The shuddering hasn't happened since I began using the AFM disabler thing.
So why is it the shuddering only happens when the car goes in AFM mode?
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That's just how it begins.
My theory, based on research and input from others here who have significant in-depth knowledge, is that your factory transmission tune (see some of it in the screenshot below) allows much more torque converter clutch slip under low, but nonzero engine load with AFM enabled ("DoD" or "displacement on demand" mode, see slip tables for 7th and 8th gear on the right in the screenshot). Therefore, the shudder is initially more pronounced in 4-cylinder mode, then as the clutches wear, it slowly appears and worsens in normal mode as well (see slip tables for 7th and 8th gear on the left).
My 2 cents' is that your goal should be to get the latest flush this week, then drive the car often and as much as you can, just as Paul_S suggested, to make sure that if you have torque converter damage, it becomes apparent sooner than later.
Should this happen, your goal is to get a new torque converter from GM via the dealer. That, plus the new fluid (part number 19417577), can reasonably be expected to fix this issue once and for all.