ELJEFFEDOR

ok so i am new here and i have a 1990 toyota 4runner with a 5spd and a 3.0 in it. Recently it has been making a sound almost like a spring being wound to tight when i am coasting in gear. not so much when i am in neutral. and now when starting out in first and second the same sound is there when accelerating not just when coasting. i am fairly mechanically inclined but am still new to toyota's. I'm normally a honda guy haha. But i took it to NV transmission exchange and took the mechanic with me for a ride to show him the noise and he said it is most likely the bearings in my transmission. i believe it is the original trans nothing has been done to the truck besides an after market intake and a flow master exhaust. there is 306689 miles on it and the trans and engine are still very strong. i'm losing my mind over this one I love my 4runner and i want to fix it any suggestions?