Going down the road car you get a sudden jolt like someone hits the brake hard. The RPM go down and about a minute or two will jump back in and go again. You can be pressing the gas but until it kicks back in you have nothing. When it happens it really clunks? Any suggestions? I now have two vehicles doing this exact same thing! My 94 Jeep is also doing this too! Seems not to do it if I take it out of OD?