1996 Trooper Transmission Problems

[KevlarB]

I have a 1995 Trooper, 162,000 miles. Out of no where, it started to studder really bad starting off in 1st gear. It's like it's catching, slipping, catching slipping. Shakes it really bad and sounds horrible. It's an automatic. If I push the "Winter Drive" button which makes the truck start in 2nd gear, it starts fine, doesn't shudder or catch slip, etc. It drives fine and will go any speed, except if it shifts back down into first, then it catches slips, etc. It I am going any speed, not in first gear and romp on the throttle, the revs go up but it doesn't speed up, like it's slipping. I took it to a transmission place and said that it was a clutch pack and that it would be $2500 to fix. Could it be anything else? They just drove it 50 feet and looked at the external of the tranny. Please any help would be appreciated.