My '96 E320 4-speed automatic seems to have more torque converter slippage than any of my older Benzes. Is this normal??

The symptoms are: Going up a hill, I press the accelerator down a bit; the RPM jumps up to 2000 and the vehicle speed slowly increases, while the tach stays at about 2100.

On my previous Benzes the RPM would not increase until the vehicle speed increased, indicating to me that the torque converter had essentially zero slippage at that point.

I'm puzzled. Is this a "feature" or a bug?