8 speed manual Mack dump truck. So the truck is an 8 speed. From gears 1-4 there’s a slight jump whenever I take out the gear. So I’ll accelerate in each gear, as soon as I take out the gear, there’s a slight pull (downward jump) that you feel in the truck. You can feel it more if you accelerate harder. Also, in reverse, if I give the gas a quick step and let go, the thump is much more noticeable. It’s strange to explain it, but the closest explanation I can give is a downward left pull/jump. I’m not sure if this has to do with it, but at high speeds, there’s a bad trembly, loose sound/feeling coming from the engine area. It’s not the drive shaft because everything is in place, has new pieces, no play, etc. Any help is appreciated!