Class 700 rough running.

[AM9]

Travelled from Farringdon to St Albans yesterday on 16:01 Three Bridges to Bedford service (9R42) which was diagrammed for 700113. Travelled in the rear car until shortly after Radlett then walked forward to car 9. On entering car 11 and then passing through car 10 there was a quite severe rumble at times sounding like a bad wheel flat but most of the time resembling an undercarriage diesel engine rumble. I've never heard that before on a 700 in many journeys at 100mph on the MML. Does anybody here know of issues with this unit?

 

[Magdalia]

On entering car 11 and then passing through car 10 there was a quite severe rumble at times

The pantograph is above car 11, and at the car 10 end. It makes a lot of noise when going through a neutral section. Are you sure it wasn't that?

 

[AM9]

The pantograph is above car 11, and at the car 10 end. It makes a lot of noise when going through a neutral section. Are you sure it wasn't that?

No this was continuous from about Harper Lane to just after Napsbury feeder point where the speed was rapidly reduced (it was clawing back a delay occuring south of London Bridge). I have done the walk forward from the declassified 1st class in car 12 to about car 8/7'ish many times to alight near the P4 exit, but have never heard such a noise before. Cars 10 and 9 are both motor cars so it seemed strange that such a low noise would emanate from below the floor but it definitely was from that direction, bear in mind that I walked directly under the car 12/11/10 gangways so had the sound emanated from above the roof that would be easy to detect. For all the reservations that some here have about the class 700s, despite the units' heavy and demanding service lifer, sub-floor issues don't seem to feature.
Maybe somebody here who has access to unit running issues might know something.