transmission problem?

I’ve just gotten a Hyundai Excel 1999, I think it’s a 1.5/1.8 L twin cam. Auto transmission with 195000km mileage. I’m currently getting a very jerky feel when I move to reverse/drive, and when I step on accelerator whilst in gear, it does not seem to want to accelerate. This happened after I replaced the left driveshaft.

I was having problems with CV joint and therefore had left driveshaft replaced. During refit, I had a bit of transmission fluid leak after pulling out old driveshaft(did not seem very significant). I quickly put in the new driveshaft and fitted everything back into place. Decided to try the new driveshaft out even after considering the leak, which I thought was not too severe. Just as I started car, it sounded like the engine/transmission was having trouble. I continued to try reverse out of garage, but after it seemed like reverse was very jerky and didn’t want to move, I stopped the car and engine.

Since then, I’ve topped up the transmission but am still having the same problems. Does not seem to be there when I’m on park/idle, but the moment I shift into reverse or drive, the sound returns, the car jerks, and refuses to accelerate both in drive/reverse. I might also add that I tested car after replacing fluid, and it seems that when I turn on the headlights, car seems to idle with a bit of problem, more effort/jerking. Just to be clear, there was no problems at all with sound/ gear change/ driving before driveshaft was replaced. Driveshaft only replaced cause of clunking sound on turning right.

Main concern is, does this have to do with the driveshaft I installed, was it installed wrongly? Or is the problem that I started the car on low transmission fluid and may have screwed something up real bad and now car requires transmission fixed?
Thanks in advance

While I dont have an Excel like yours, I can tell you that having the transmission be a couple of liters low on fluid will not hurt it in any way - unless you drove it that way for a long distance; like hundreds of kilometers. Having it filled up should be checked out though. It takes a little driving or running the shift lever through the gears to get the air bubbles out of the transmission, if its been very low. So be sure to check the trans fluid again, with the engine idling and in Park. It may still need more fluid.
And while I cant imagine anything could be wrong with an axle shaft that would cause your symptoms - I CAN believe that something else was disturbed by the process of replacing the axle, and needs to be fixed. Im think of a connector being loose somewhere (I think your transmission has electronic controls), or the trans isnt getting a signal as to the position of the gas pedal. This would involve some connection to the car's computer, or at least its transmission control module.