Transmission shifting problems

[Hatterasguy]

Now it is shifting funny, although I don't know what "normal" shifting is for a MB diesel. The 1st 2nd and 3rd 4th shifts are normal I guess, pretty hard by American and Japanese car standards. But the 2-3 shift is real hard, almost "banging" Like I said I don't know what normal is but this deffinitly does not feel right. I think it just started to do this but am not sure because I really have not driven the car much yet. So what could this be? The fluid looks fine a little dirty but not burnt, it is also a little overfilled. Would that do it? I'm a little ticked because I thought it shifted fine, last week I think it did.

Also has anyone ever tried Trans-X to stop a leak? My uncle swears by it, but I'm affraid it will losen stuff up and cause more harm than good. The car is a 1987 300SDL, I don't know the service history but the fluid looks good. I will be changing the fluid and filter in the next few days.