I've got at 1997 Chevy Suburban. Recently we had the fuel pump changed, because we hit a bump and it gave up the ghost.

In the last month there have been at least three times when we we've stopped, and then started, but instead of shifting into the next gear it basically shifted out of gear - the RPMs went up, but the speed went down.

After letting off the gas, then things re-engage and we can drive off. But it seems to have happened when we're trying for a quick acceleration, say because a semi-truck is coming up behind us.

I know that at least two of the times have been turning from a near or full stop. Last time I changed the oil they also mentioned that our differential fluid needs changing - it was pretty burnt up. Could that be related?