Is this the same transmission for which you posted "3 speed trans noise"?
1st and second gear noise. Goes away when clutch is pushed in?
It only does it when I give it gas?
You need to start the symptom description again and be more specific. When and what does it sound like.
1. Engine running & transmission in neutral. Clutch in and clutch out. Rev engine and any associated noise.
2. Engine running & transmission in 1st/2nd. Truck is on the road. Clutch in and clutch out. Rev engine and any associated noise.
The bearings are usually reliable but can fail if no lubricant or contaminants (chip gear teeth or synchro bits) in the bearings.
If you are sure it's in the transmission then removing the side cover and having a look inside is needed.
http://chevy.oldcarmanualproject.com/booklets/55top13/index.htm
