trans shifts hard in 1 and 2 gears

Is the check engine light on? Are there any codes stored? That would be the first place to start.

//2000CAYukon

check engine light is not on any more
ran low on fluid once got trans serviced

the check engine light is not on how do you check for stored codes

Some Autozones will loan out a code reader. Since you have a 96, you need an OBD-II code reader to see if any codes are stored.

//2000CAYukon

Thanks Much I'll Try Autozone