Jackcob, what records specifically are causing this rumble? That will give a clue. Like I said before, the Underground's rumblings are clearly audible on the British RCAs, throughout the recordings, and Classic's reissues are good enough to capture them (that's one of the reasons Carnegie Hall and Trinity Church in NYC are not favored recording sites, good as their acoustics might be, as the subways are clearly audible, and felt, in those places). Only other alternative I can figure is whether the records have any warps.
By the way, there's a story as to one of the London halls which was an excellent recording venue until an Oriental rug dealer went out of business--he stored his rugs under the main floor, and when they were liquidated their damping effect on the Underground was lost, making it impossible to record there without too much interference from the trains.