At first I thought the issues were related, now I’m slightly worried they might be two entirely separate things.
I have a 97 Lumina sedan. When moderately accelerating between 50-60 on a slight incline, the car will sometimes start to “jolt” a little repeatedly. It continues to do it if I hold the pedal steady, but if the incline goes away or I press the gas pedal to accelerate harder the jolting will stop as abruptly as it started. The magic number seems to be around 55mph, never outside that range. I can reproduce it on certain interchange ramps or hills, but only in overdrive. Regular drive gear doesn’t do it but the engine is at a much higher RPM. If I accelerate harder than I usually do it also doesn’t seem to occur.
At first I thought it was just the same RPM loss issue at speed in a low cruising RPM, something that happens infrequently at idle. But now I’m worried the specificity might indicate a transmission problem. Car only has 87K miles on it for its age though. Any insight or advice would be greatly appreciated! Thanks for reading!