90 tbird cruise control weak..

had the problem since I got the car, some 35,000 miles ago.. the cruise control works, but when confronted with even a mild uphill grade, I get to watch the (digital) speedo gradually drop..
if the hill is big enough, it will get to 10mph under the set point and give up and shut down.. I need to tear the dash apart to replace the heater core anyway, so while I'm at it, just exactly where should I be looking?
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not under the dash.. unless there's a vacuum leak under there. Esp the dump valve at the brake pedal assy
Get a vac gauge and pump, hook it to servo vac port and see if it will hold somewhat of a vacuum.
Call a scrapper and get the price of a used servo ... there should be plenty of them
There's a time to "throw parts" at a problem and I would inspect all the lines for kinks and leaks, and if I found none, i'd just replace it.
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well every vac line not going into the firewall has been recently replaced, and I have a cable from the throttle and a vac line(which looks fine for the whole 3 inches I can see)disappearing into the backside of the fender well, so I'm assuming the servo is under the dash?
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No... it's in the fender, behind the wheel. Take off wheel, take off inner splash. Not hard
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servo located in fender well,not in dash.
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