Hello Scotty! I have a 1997 GMC Sierra K1500. Recently it has this horrible bucking issue to it. You can feel the pressure build up, and if you don’t let off the gas when it first starts to build up, it feels like you are literally riding a jumping horse. But the thing about it is, sometimes it will do it terribly wherever you drive to, and then when you park it and get back in it, it runs like a top. The truck also misfires. It has had a new distributor cap and rotor, but I still can’t get to the bottom of these issues.
@maples5430
Common fix for a tricky misfire on these is the intake manifold gasket.
I'm willing to bet your rear end is going out. Its fairly common on these.
@cjbman
It doesn’t appear to have any exterior signs of wear, but how can the inconsistency be explained? Going from place to place, you never know which truck will be sitting outside. It has two personalities.
When it does it try going back and forth between reverse and drive and see if you can get it to free up. I'm assuming its got a few missing teeth on the pinion or something and you hit the flat spot when it acts up. If the bearing supporting the pinion is too worn so it doesn't make full contact on the ring gear all of the time. But I do know for a fact that these rear ends are notorious for going out.