240 DL sedan 1989 160K miles B230F automatic

I've had the car for almost a year. I've done everything on it wrt maintanance zero-mileaging and care...

I always drive the cr with a light foot. I have never had any problem with drivability or idling or engine/tranny issues. It's really been great, and continues to be so.

Last night I decided to try pushing the pedal near the floor. Strangley I realized that the engine would not hold high RPM without upshifting. No matter how hard I push on the gas, it would not go beyon 3500 RPM without upshifting. It continues to pull well, good torque, good power. Sounds healthy.

Why is this? Is there a vaccum that is responsible for holding the gear in place? I don't know anything about auto tranny gear changing...

My comparison is to my B234F 16v in my 940 GLE, which revs easily. I know not to compare the B230F with the B234F in that respect, but I see no reason why I can't push the 240 to at least 5000 RPM before shifting.

Note it idles very nicely. It seems to rev up high at neutral, but I still feel some minor resistance... not sure.

Advice?

Thanks,
Greg Mustang
Montreal-Ottawa
Canada