Is the fluid clean or dirty? If dirty flush jt out and replace. Also do you have a heavy bumper or big tires that add pressure to the pump? Sorry an on my phone and can't see your signature. They make a replacement fitting for your power steering pump that will make your wheel spin easier with bigger tires or a bumper. Not sure of the GM part number at the moment but it can be replaced.
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2008 GMC 2500HD LMM SLT CC SB 4x4 Z71
Buckstop front bumper, WARN M12000 winch, PIAA 520 ATP driving / PIAA 510 fog, Westin Platinum Series nerf bars, Pace Edwards Bedlocker tonneau cover, Cognito UCA leveling kit and HD Idler Pivot Assembly, Cognito Pitman and Idler steering braces, Bilstein 5100's, LT285/70R17 BFG AT KO tires, 17 x 9 XD Series Crank Wheels, 15% Tint Driver/Passenger windows, GM Tow Mirrors, DDM Tuning HID lights 6000K 35W