MCL1981 wrote: How do the old clunkers deal with gaps?
Not very well.
The low voltage systems operate similarly to all the other cars. The HVAC systems (as in the 4000s) are all DC drive motors which operate much quieter so people usually don't notice them slowing down through gaps.
The biggest flaw (IMO) with the 1000 cars was the choice of hydraulic friction brakes. Each car needs to be on third rail at all times to keep the hydraulic power unit running. If a car is gapped for more than just a few minutes, hydraulic pressure will drop below a safe threshold resulting a full emergency brake application. The BIE condition will disable the train until power is restored.
With air brakes, this isn't a big deal as air can be shared between cars to make up for a gapped or even failed air compressor. Not so with hydraulic brakes.