I have a 1997 GMC Sierra 4wd. I recently had the transmission replaced. Now sometimes usually when it is cold I'll put in gear and sometimes I have to wait 3 or 4 seconds before it will go into gear. I give it gas and it is like it is in neutral. Is there any vacuum associated with the transmission. Also sometimes when I take off it will slip out of gear, and feel like I'm neutral and go back into gear again. This is becoming annoying. Can you guys help me out. Also I have no engine codes.

I have a 1997 GMC Sierra 4wd. I recently had the transmission replaced. Now sometimes usually when it is cold I'll put in gear and sometimes I have to wait 3 or 4 seconds before it will go into gear. I give it gas and it is like it is in neutral. Is there any vacuum associated with the transmission. Also sometimes when I take off it will slip out of gear, and feel like I'm neutral and go back into gear again. This is becoming annoying. Can you guys help me out. Also I have no engine codes.

It is possible that the fwd accumulator is leaking either at the pin or seal. See http://www.transmissionspecialty.com/parts/parts/77754-01K.htm

Of course, the clutches could also be burned.

//2000CAYukon

Sound like the fluid could be low also

Check for burnt fluid on the dip stick, which will indicate clutch wear.