FLT CREW OF P180 DIVERT TO AN ENRTE ARPT DUE TO RECURRING ROLL TRIM PROBS AND STIFF MANUAL ROLL INPUTS.

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WE HAD LEVELED OFF AT FL330; ENRTE FROM LAX TO JAC AND WERE NE OF LAS; CLRED DIRECT TO MLF. THROUGHOUT THE CLB; WE HAD BEEN EXPERIENCING EXCESSIVE AUTOPLT TRIM ROLL COMMANDS. PERIODICALLY; I WOULD DISENGAGE THE AUTOPLT; TRIM MANUALLY; RE-ENGAGE THE AUTOPLT AND THINGS WOULD BE FINE FOR SEVERAL MINS. LOTS OF WIND SHIFTS ON CLB AND I THOUGHT PERHAPS THIS WAS BEHIND THE ROLL TRIM. FOR SEVERAL MINS AFTER LEVELOFF; THE AUTOPLT SEEMED TO BE FUNCTIONING FINE. THEN; ONCE AGAIN; EXCESSIVE ROLL TRIM BEGAN AND THEN THE ACFT STARTED AN UNCOMMANDED TURN TO THE L (W). I LET IT GO FOR A MOMENT TO SEE IF IT WOULD CONNECT AND THEN IT WENT THE OTHER WAY (E) -- UP TO 45 DEGS OFF TO BEGIN. I DISCONNECTED THE AUTOPLT; RETRIMMED BUT THE YOKE WOULD BARELY MOVE -- ENOUGH TO MAINTAIN CTL; BUT DEFINITELY NOT 'NORMAL.' I ENGAGED AUTOPLT WHICH I DISCUSSED THE ISSUE WITH MY COPLT. GIVEN THE WX AT DEST AND OUR PLANS FOR THE DAY (XCOUNTRY TO TEB EVENTUALLY WITH MINIMUM WX THE WHOLE WAY); WE ELECTED TO DIVERT. WE REQUESTED LAS AND CTR VECTORED US. ON DSCNT; HAND FLEW AND CTLS SEEMED NORMAL ONCE AT LOWER ALTS.