Hopefully someone else has run into this problem.

I've got a Cat F30 (5CB serial number) with low power to the drive wheels. The current limit is at 90 and 160 amps and causing low drive power. I cannot adjust the C/L any higher. The transistors are within tolerances and I even tried replacing them to see if it would make any difference. A rebuilt logic unit also don't show any difference. I used a Handyman to test all of the large diodes. High speed works fine when the 1A contact pulls in so I assume that the drive motors are ok.

Any suggestions on what could be wrong? Capacitor? Or driver board?