Do you have any codes?If so what are the exact code numbers you have?2Nd gear and reverse use the same clutch pack because reverse doesnt have its own clutch pack. As far as reverse and second gear go it could be too low of pressure inside the transmission or a loose input shaft nut or a leaking second gear piston. As far as 4th gear goes it could be a low pressure issue or leaking 4th gear piston. From what you have described I would guess a low pressure issue. Those are caused by the pressure regulators in the transmission valve body sticking in the bore causing low line pressure inside the transmission. Very common on those cars I had a line pressure issue on my 1999 SL2 saturn I bored the pressure regulator bore out and put in the sonnax sure cure kit with a sonnax pressure regulator sleeve pressure regulator pressure regulator spring boost valve and boost valve sleeve. It shifts must firmer now. If you want to diagnose this problem yourself it not going to be real easy. You will have to buy a transmission pressure gauge set I recomend the otc one that I have nice set a multimeter you might need.A air compressor to air check the clutch packs. Tools to take the air intake off battery out battery tray and transmission valve body cover. The first thing is see what codes you have. Are you up for the challenge?