My brother has a Case 1840 that is usually ol reliable until recently it has developed a steering and drive problem. It will sit and stay in neutral just fine until you go to move. What happens is there is no lil bit once it starts to go it's all or nothing which makes it impossible to safely operate. Anybody else ever run into this issue?
Are you saying it will creep . Like handles are not returning to neutral ?
Not real sure from the description what is happening but the first thing I would be checking is slop/free play in joints in the linkage from hand levers to the pump and next would maybe be to remove all linkage from the pump and work the levers on it by hand to see it=f they move smooth or lumpy. Might be best to block the machine up so all wheels are off the ground while checking things out.