GMC Repair: th 400 transmission, turbine shaft, clutch plate

Question
I have a 1989 chev k 1500 305 engine turbo 400 trans
It,s having a hard time going into reverse,a quick
shot on the gas will make it go in. Is there any thing I
can check or repair with out pulling the transmission.
It works good in all other gears, and reverse has tire burning power when it is in gear

Answer
Hi
Assuming you have good fluid and good fluid pressure, here is a list of items it could be:
Input Housing Assembly
3-4 Apply ring stuck in applied position
Forward clutch not releasing
Turbine shaft seals missing, cut or damaged  
Manual Valve Link
Disconnected
Valve Body Assembly
2-3 Shift valve stuck
Manual linkage not adjusted
Spacer plate and gaskets incorrect, mispositioned or damaged
Lo overrun valve stuck
Orificed cup plug restricted, missing or damaged  
Reverse Input Clutch Assembly
Clutch plate worn
Reverse input housing and drum assembly cracked at weld
Clutch plate retaining ring out of groove
Return spring assembly retaining ring out of groove
Seals cut or damaged
Restricted apply passage
Porosity in piston
Belleville plate installed incorrectly
Excessive clutch plate travel
Oversized housing  
Lo and Reverse Clutch
Clutch plates worn
Porosity in piston
Seals damaged
Return spring assembly retaining ring mispositioned
Restricted apply passage
Torque converter drainback.
Hope this helps.
Good Luck
Pawl