I have a rust free low millage '84 Vanden Plas, but the windshield wiper transmission cable snapped. It appears the dash has to be pulled to replace it. Does anyone have any suggestions as for the best way to fix this issue?

 

not really, you can

a) remove the motor, by disconnecting it from the mounting clamp and wiring plugs, then pulling the cable and motor away from the car,

b) if the cable is broken (I doubt it), just remove the dash Cap, (top of dash) and you can remove the two wiper boxes and tubing system. (first remove the wipers, then the dash cap).

I suggest you take a video or clear pictures of how everything is mounted before removing anything, there are a series of tubing sections between the wiper boxes and they have to go back in the proper order.

mechanically, it's a very simple system and very lame and ineffective too. All Jags since the 1950's use the same cable system.

a typical symptom is that the cable is slipping inside the box shaft gear, and the remedy is to tighten the two nuts holding the box cover, they might be loose.