Volvo Repair: Brake shudder on 850R wagon, steering wheel, stong

Question
I own a 1996 850r wagon done around 140,000kms.
On slowing to a stop the car has a stong shudder which isn't present if you brake to a sudden stop.
although the shudder can't be felt through the steering wheel it's impossible to tell where the shudder comes from ( front,back or both ? ).
No amount of changing tyres brakes,disc's etc has made any difference.
I'm stumped and so is the mechanic !! any suggestions, please.....

Answer
the only thing I can think of like this is a loud ressonating type vibration on this type of braking.which happens if you are using volvo pads that are a later pad found on a S70 model which do fit this model and is OK to use however if you use this pad you need to install the shims which are a half cut shim and not a full shim.there is a bulletin on this.