i have a 87 IROC with a 700R4. i am getting a whinning sound coming from the tranny, as i rev the motor it starts to get louder and it shifts kinda funny. while driving as it shifts into 2nd gear, it shifts, the rpms come up, and them it engages into gear. it does go into every gear though and the fluid level is fine.

 

Sounds like what my first tranny was doing. Most likely its your torque converter slipping. Check the fluid, see if it looks darker than normal, like its been burnt. This is a good sign of a slipping convertor. My tranny lasted for 5000 miles after the TC started slipping, but I would still be prepared for it to go out.