Various problems with my 1992 Nissan Sentra XE (4 door)

[benenarmor]

1. My transmission
I have an automatic tranny and sometimes when it shifts gears, it will hit real hard. Almost like if you are in neutral, rev up, and throw it into drive. It will do if I am accelerating fast, or if I'm already going kind of fast (around 50mph) and let off the accelerator and press it down again. The stock wheels are around 13s or something and I put 17s on it. (Not my first choice, but I got what I got). Would the bigger wheels have something to do with it?

2. My fuel gauge
It randomly doesn't work. It has been working most of the time lately, but still when it is on empty, I have like 4 or 5 gallons left. It used to work backwards, or not even work. What could be wrong?