1) First issue: I drive an automatic, my car vibrates hard when I slow down and get to about 20mph. It seems like its the transmission. It seems like its having a problem going back into first gear from a higher gear.
2) Second issue: My tire psi keeps going up and down by about 5psi. Is it because I have economy tires or is it do to temperature change.

 

I need advice as to what may be wrong with my car, can I get some help, please?

 

for the first issue, does it just vibrate when pressing on brake pedal or does it do it all the time when slowing down for example when just letting off of the gas?

second issue are you always checking pressures when cold? or are you checking pressures just whenever you want to?

 

I believe it vibrates in either situation. Can you give me some advice for either situation? As for the tires, I check the psi at both cold and hot temperatures. It may be 80' one week and then 65' the next, and then I notice the difference; or it maybe the change in temperature from night to day.

 

first issue, if only vibrating when braking, most likely bad/ warped brake rotors, if vibrating all the time when slowing down, possibly a transmission shift modulator? i know the older chev product had one and i believe they worked of of a vacume. but i am not too shure but it is worth asking a dodge dealership about if your tranny has one.

second issue. tire pressures are to be checked when cold ( not driven for a couple of hours) and temperature changes from day to day and before and after driving will make the temperature change a little bit like you have noticed.

 

It'll also shake at slow speeds while going up a hill, what might be the problem with that situation, the tranny?

 

is the level of the tranny fluid correct? when were your tires balanced last?