Same thing happened to me two weeks ago... Unfortunately, these transmissions have a bunch of known problems, and it was not until after about 2003 that they started making them with better parts... There is a high probability that the problem you are experiencing is due to a worn out spline on the 4th gear clutch hub, which is one of the many common problems that these transmissions experience... After 2003 or so, they started using heat treated shafts, which are much stronger... All in all, I regret to inform you that your transmission is probably going to have get rebuilt... This is not necessarily a bad thing.. Like I said, I just had mine rebuilt last week.. It was not cheap, but well worth the investment if you want to hold on to the car.. You could also just get a brand new transmission.. There are pros and cons vs getting a rebuild, or buying a new transmission... Aside from how costly the rebuild is, the biggest pain in the rear is finding a reputable tranmission shop... Fortunately, I got lucky and was recommended to an A+ shop right down the road from me... What I have told you is alot to absorb, and some of it you may know already... but if you have any more questions, I would be happy to answer them..