Haas TM1 won't drive a 1/2 inch tap

I occasionally run a Haas Tool Room mill. It is about 8 years old. We've had it for about 5 years.

In that time it has always had what I call a "rotational torque" problem. It will occasionally stall out when trying to drive a 1/2 or larger tap. It also stalls when trying to drill a hole around 5/8 inch or bigger. The "Load Meter" goes into the red and stops the mill. It will drill but it can't handle very much feed.

Any ideas if this is normal on this style mill and if not, what can I do to fix it.

Thanks for any info......JW