Quote:
Originally Posted by arpad_m
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.
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Thanks for posting.
I’ve been keeping an eye on this thread & paying close attention to whether or not my car exhibits any of the symptoms. Up to about 19K miles I didn’t detect it. Even took it on a 1K mike round trip from Northern WI to Indiana back in September & did not notice it. Then in November, about 200 miles after the trip I noticed some slight RPM fluctuations when AFM activated. Then winter came with a vengeance & the car will not see a road until mid-April.
If the new TSB calls for a fluid replacement without diagnosis I just may have it done right away this spring to prevent any damage to the TC.
I’m in a predicament as I still have over a year left of the GM 3/36 B2B & the dealer I purchased it from gives a lifetime power train warranty, but I’m getting the itch to start modifying it.