Trans shift problems
 

My boss has a 99 5.9 2wd with the 46re, anyways he replaced the the filter and fluid with 4 qts of ATF+4 and now it will not move in any gear. The truck has around 190k on the odometer and a unknown service history with the trans. He got if for $500 and was trying to fix it up , any ideas guys why it wouldnt be shifting at all before the pan drop and filter and fluid change it was slipping slightly from 1st to 2nd. Any help would be appreciated and he is my boss so I would like to impress him lol so help me out!

he should have had the bands adjusted, and i would check the fluid level

+1 shrps

4 quarts sounds like he didn't put enough fluid back in it. It takes about 6-8 quarts for a trans filter/fluid change.

To check the fluid level properly the truck has to be up to full operational temperature and the engine running in Neutral. Now there is a cold fluid mark on the dip stick but that will only get you close.

First you start the engine, shift between each gear holding 2 seconds between each selection (this get the air out of the passage ways), all the way down then all the way back up, then shift to Neutral and set the E-brake. With engine running and in Neutral check the fluid level and add accordingly. make sure you do NOT overfill the transmission! Get it close at cold then check it after it is hot.

it drove fine then nothing any gear

Is the linkage actually shifting the transmission?