Suburban A/C noise/viberation problems ?

Question

GMC Suburban 1990 454 auto.
viberation and noise ONLY when A/C is on

i found that the compressor brackets and front bracket (triangular with 3 or 2 wheels!) not in proper shape and cracked so i changed them along with (the belt tensioner) and of course the belt itself
i replaced the small supporting bracket behind the steering wheel (oil tank/box) too
the noise almost disappeared but i still could feel it when the car is stoped (braking when the gear is on Drive)
visualy all the pulleys seems to be on line

unfortunately no mechanic could determine whats exactly wrong one suggested that the steering wheel pump, tank and lining is not working properly and need to be replaced but i was not convinced bcuz he wasnt sure and it was alittle bit expensive to replace for a guess!
(please excuse my poor language and mauve knowledge of the parts names)
what, else, could i do to get rid of this noise ?

Answer 1

Looks like to me, given the age of the vehicle, that the compressor is failing... if memory servers, they use a V- inline piston type compressor on those so that is where I believe your problems are.
Plan on replacing:
compressor
Expansion tank
Orifice tube
which will effectively convert you to R134a, if it hasn't already been done.