[ECKOdotCOMPLEX]

I own a 1998 GMC Yukon. now heres the problem. Today i noticed a weird whining sound from under the hood when i was driving down the road. no problems except for the whining. then when i was parallel parking and i put it in reverse it seem like the car was going into gear but then getting kicked out. then when i was taking a friend home i stopped at a stop sign and when i started going it seemed like it wasnt catching the gears or anything...it seemed like it was in netural. it was reving up really high but wasnt going anywhere. so i turned the car off and started it. next thing i know it caught a gear and i drove off...but then i could only stay in first gear or it wouldnt go anywhere. i found this out because when i used (D) it was being hella jerky. so i popped it down into first. so im driving and i kicked it into second gear and then it just felt as if it was in netural. so after i dropped her off and headed home i was doing like 20 mph at 4.5k rpm's. so im like..."ok...this is going to suck on gas" so i pull over and stop the car. then i start it and all of a sudden i have all 3 gears. they all worked fine...enough to get me home that was. so what im wondering is if im going to need a new tranny soon or what. thanx