What causes delay in gear shift

My friend bought a 1988 e28 520 automatic and he is complaining the car's gear shift is hesitated. Everytime he put the gas, the gear is shifted from 1st to 2nd @ around 2500RPM. I tested his car and I feel that when I put the gas, I have to release the gas to let the gear upshifted. A couple things I suggested him are check the spark plug, replaced tranny oil and change engine oil. Any recommendation?

Originally Posted by VitaminXX

My friend bought a 1988 e28 520 automatic and he is complaining the car's gear shift is hesitated. Everytime he put the gas, the gear is shifted from 1st to 2nd @ around 2500RPM. I tested his car and I feel that when I put the gas, I have to release the gas to let the gear upshifted. A couple things I suggested him are check the spark plug, replaced tranny oil and change engine oil. Any recommendation?

Without getting complicated and expensive the only other things I would recommend are to make sure the engine is running well, and change the trans fluid and filter. I always use only synthetic trans fluid.