Why does my 2001 Ram 1500 5.2L v8 bang at about 40mph every now and then?

It happened twice. At about 35-40mph, like
when it was shifting from 3rd to 4th, the
truck made a loud bang like something
slammed underneath and jerked it forward a
little, about 2 seconds later, again and then it
was fine. It did it once before a couple
weeks ago. I am getting a tranny flush
tomorrow at the dodge dealer cause I know
it needs it. But I also think the plenum pan
gasket could possibly be blown. I feel like it
is consuming a little oil. I am trying to
remove the air filter housing but there is one
piece connecting at the bottom with a
rubber washer or something between it and
it won't come loose. I am trying to see if I
can see oil pooled up which is for sure sign
of the gasket being blown. It's got 77k miles
on it and is clean as can be. Nice truck and
would love to figure this out. It scares me a
little. Any help would be really appreciated.
Thanks for your time guys