I have a problem with random shifting between 3rd and 4th gear. 1st and 2nd operate just fine but, when I shift to drive "D" that's when the jerking starts. RPMs stay constant throught most of the jerking. By random I mean 20 to 30 jerks over about one mile. Could this be the 2-3 accumulator shift spring or maby the shift relay. Tks for any response. Bob