My transmission is slipping

I put transmission does not drive I ment just slips when it tries into shift into drive.

Not worried bout the transmission I have a used one I need to get it started

This is my question maybe it didn't show up. I have a 2000 chevy with the 4.3. I recently bought. The transmission does not have drive and had been setting up for a year. When I purchased it I started it up and it ran smooth. When I went down the street testing it out it had what felt like a miss or dead spot in the accelerator. I was gonna just drive it home with 1&2. I drove it around 15 miles and the dead spot started getting worse. Until it eventually died it the I then started it back up and made it about a half mile with it spitting and sputtering before it died again. The check engine light had came on while I was driving I had it towed and the tow truck driver left it switched on and it reset the computer apparetly. It will start and run rough a few seconds then die. I checked the filter its clean I did a fuel pressure test its at 65 when switched on and 55 while spinning over. I took the upper intake off and checked the spider injector to see if its spraying fuel. And it is.I put it all back together and it still wont start. I then bi passed the fuel pump relay and it still not starting. I also checked the spark by using a spark plug and got good spark. I also unplugged the mass flow sensor to see if it would start with out it still nothing the same thing as before maybe worse

It will but it doesn't stay running it does bout the same with or with out cleaner being sprayed in it I might get a few more seconds out of it before it dies. I will try unbolting the exhaust. It never smelt like rotten eggs or smelt like it was getting hot. Just acts like its out of gas but I had just put $30 in it

K