This is a 1997 Tahoe Suburban four-door 5.7 L V8. I'm pretty sure it's not low transmission fluid because it was recently topped off. If I drive for a long time on the highway and then come to a complete stop, then start to accelerate again, there is a loud clunk. Almost like being rear-ended lightly. Then everything goes back to normal. Happens extra often if I'm towing my trailer with a lot of weight. Is this a "sell the car quickly before the transmission totally fails" situation or a "don't worry, that's a common error and everything is fine" situation? Any advice would be appreciated. I should note, the car is running perfectly fine other than this error code and that occasional weird clunk.