How do you replace the alternator belt on a 2001 gmc Yukon 5.3 liter engine with 130amp alternator?

Go buy a Haynes Auto Repair manual for your car.

So far as I know there is a serpentine belt on this car, no alternator belt per se'.

Go buy a Haynes Auto Repair manual for your car. It's all in there.

First, disconnect the negative battery cable. Next, hook up your charger - since your alternator's bad, your battery is undercharged.

pull the rubber boot on the back of the alternator, remove the brass hex nut, and remove the wire. Replace the nut on the shaft. Then, pull the multiple wire plug from the 11:30 position (just left of the top of the alternator) -- there's a plastic clip on the back which must be pulled toward the back of the vehicle.

Next, use a breaker bar with 15mm socket or a long 15mm end wrench to turn the hex head on the tensioner pulley (It's on the passenger side at the front of the motor, fairly high) toward the driver side about a quarter turn or so, to release tension on the belt so you can slip the belt off the front. Carefully release tension on the 15mm wrench.

Remove the long bolts from the bottom front of the alternator. Use a long strong screwdriver to pry the alternator up from the cradle, one side at a time.

Set aside the old alternator, and put the new one in the cradle. replace the 2 bottom mounting bolts and tighten pretty good but don't break the casting. replace the 2 wires. Using the 15mm wrench, again release tension on the belt tensioner, and while holding it in place, put the belt on the new alternator pulley. Carefully release tension. Use a bright light to be sure the serpentine belt is properly seated in all the pulleys (crankshaft, water pump, PS pump, alternator, and tensioner. remove all tools from under the hood.

Using your voltmeter or multitester, check that you have at least 12.4 v DC from the battery. replace the negative battery cable. start it and check the voltmeter for 14 volts. Return the old alternator to store for credit. You're done, but check the bolts in a week, just to be sure.