On or around Thu, 31 Jul 2003 05:33:50 +0100, "Mike" enlightened us thusly:
I recall when they first changed the London routemasters to a transmission that would work fully-auto, though still with the old AEC low-speed engines, you could tell the old drivers from the new ones - new ones banged it in D and put their toe down, whereupon it changed up with a great lurch, especially from 1st to 2nd, probably because the AEC had a raft of torque available at the lower engine speed once it'd changed gear. The old drivers still treated it like a pre-selector and over-rode it, then backed off the power to let it change. 'course, the surviving routemasters have now been fitted with modern iveco engines, which are better no doubt in most respects, except for the lack of the characteristic "boggler-boggler-boggler" idling sound, which some of us thought was a pity.
mind you, to get back slightly more on to topic, the RR-ZF auto, if you treat it in "D-and-forget" mode manages some surprisingly uneven changes on occasion, and it's possible to persuade it to behave better.