Dear jd620,

Hope you're well and stay so. I have never heard of - or seen - for a 940, a one-piece brake rotor and hub unit.

According to Volvo VADIS - a superseded dealer parts and service database - the one-part design (rotor and hub unit) ended with the 1987 model year, i.e., long before the 940 was produced.

For 740s produced in and after 1988 - at least for North American markets - the hub and the rotor are separate parts, i.e., they may be replaced independent of each other.

Your mechanic - perhaps unfamiliar with the 940 - seems to mistake a rotor corrosion-bonded to the hub, for a factory-supplied unit. I do not believe that Volvo ever sold a single hub-and-rotor unit for the 940. The reason: front rotors need to be changed periodically. Hubs can last for 200,000 miles, absent collision/road hazard damage.

I'd squirt PB Blaster, Kroil, or a similar penetrating oil, at the base of each of the studs, on which the wheel is mounted, where the studs protrude through the rotor's outer surface.

With time - and gentle tapping on the edge of the to-be-replaced rotor - the penetrating oil will permeate micro-channels in the corrosion. This will weaken the corrosion bond. The rotor will then come free from the hub.

The hub's face should then be cleaned of corrosion with a rotary wire brush, on an air-powered grinder. Once all corrosion has been removed from the hub, a thin, even coat of nickel anti-seize should be applied to the hub's face. That will keep the new rotor from bonding to the hub.

Hope this helps.

Yours faithfully,

Spook