Markynoodles

Hey Everyone, My 76 series landcruiser is doing something strange typically in 2nd or 3rd gear where by when I go over a bump (ie pot hole, dip etc) it drops power and I really need to put the boot into the accelerator or drop gears to gain any power. From what I can see there doesn't appear to be a reduction in REVs when this occurs. Has anyone out there experienced or heard of this issue before? Thanks, in advance.