1997 Ford Ranger Jarring Bump when starting off or stopping

Experiencing a definate jarring bump when taking off from a dead stop. Also the same bump occurs when coming to a complete stop, just at the last moment.

The transmission seems to operate fine as far as shifting in all regards with maybe this exception, if it is actually a transmission issue?

It is in 2 wheel drive during this event, driving on city streets. I haven't tested it in 4 wheel drive. If I really baby the accelerator when moving from a stop I can sometimes avoid the event.

The transmission fluid has been checked and is OK. The overdrive function seems to work OK.

There is a vibration that is distinct that occurs at 55 mph and above that I'm not sure is related.