2001 LX Started Bucking

Hey all, I recently bought an 01 crown vic lx with 128k on it. I did a full tran fluid replacement (drained torque converter) and filter as well as a oil change. Car seemed to be running fine for about 2 weeks. One day after traveling 45 miles home from work on the highway I pulled off onto my exit and while accelerating I notice the car start to buck just a little, but it went away after only a second or 2. Driving the car a couple of days later I noticed it again after pulling off the freeway turning on the street my job is located. Kept driving the car for a few days with no issue. Couple day later I notice the bucking again while going to the store about 15 minutes away and this time the bucking lasted a bit longer, about 15 seconds while I held my foot at a consistent throttle position. Then today, while coming home from work, I accelerated relatively hard onto the entrance of the freeway as some chump was up my ass. The car started bucking soon after and pretty much all the way home. I stopped into a parking lot and looked under the car. There was some fluid at the differential where the drive shaft bolts to the yoke for the pumpkin. I thought that was a bit unusual but perhaps the bucking had caused some fluid to spurt out of the differential input seal.

Just to add, when I would go over a bump at slow speed the car seemed to should clunkier than usual. I also felt that there was more wiggle in the seat of my pants then usual.

So here are my thoughts. Do I have a bad 'Coil on plug'? Is the torque converter shot? Is the trans clutch shot? Do I have a bad universal joint in my driveshaft? Is the rear end toast?

I love these cars, I used to own an 87 and recently bought this 01 as well as a 08 CVPI. I used to work as a mechanic when I was younger, no internal engine stuff but I've replace engines as well as transmissions a time or 10. Currently I don't have a garage and have to do all my work shade tree style. That, and I'm not quite as young as I used to be. Help form an expert would be greatly appreciated.

So I had the transmission issue these cars see quite a bit and it is a bit more of a shudder at speed not really a buck like you are describing. So I really do not think you have a transmission issue from your description. I would check the following:
1. check your coils and plugs make sure none of them have backed out (super easy and fast)
2. check your Fuel pressure, there is a check port on the rails that looks like a tire valve stem, make sure the pressure is constant. (I had this bucking behavior and it turned out it was my fuel pump dying)
3. if the first two look good service the rear end look for any metal in the gear oil. If you find metal shavings time to rebuild the rear end. Rear end rebuilds on these axles are relatively easy and if you don't already have a limited slip throw it in.