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© 1997 Brian F. Schreurs
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The underdrive kit from Auto Specialties (part #825928 for aluminum black) comes with three pulleys: alternator, water pump, and crank. The pulleys look sharp in satin black, and they come in steel or aluminum. Ours are aluminum to save weight (not a lot of weight -- we weighed them and came away with about a two pound savings). It claims the job can be done in 30 minutes, but warns that an impact wrench is necessary for the alt pulley. After having a look for ourselves, we agreed, and planned the job so that we could take the alternator to a shop.

The original pulleys are on the top; the new ones are on the bottom. (L) Water Pump; (R) Crankshaft.

We stupidly spent some time playing with the Paradise Garage Charger when we should have been working on the visiting Mustang. By the time we got to work, we had an untouched car, two guys who had never pulled a Mustang alternator before, and 60 minutes to get to a shop 20 minutes away. This is not a good way to start.

First, unplug the battery. This is an extremely important step, and if you forget, you will be reminded in the next step. We remembered.

Now unplug the alternator. The two little wires are just clipped on. Use a skinny flathead screwdriver to pry them off. The third, big fat wire, is bolted down. The rubber boot is just that -- a boot. Pull it forward to reveal a nut holding a terminal onto a stud. We have no idea what size that nut is, except that it's metric. There's no room for a socket wrench so you have to use a crescent wrench -- only, we don't have any metric crescent wrenches. Who woulda thought we'd need metric on a 5.0 Mustang! So stock up. To get the nut off, we used a needlenose vise-grip. Pull the wire harness clear of the work area.

The Alternator Is In...

There are three bolts holding the alternator in place. It is also resting on a cradle, so you need not worry about dropping it onto anything expensive. Wrench away.

We started with the one in the back. We found, with a little finagling, that a 1/4-in. drive socket wrench could fit back there. The bolt is 10 millimeters (yes, we have metric sockets).

The top front bolt comes out easily enough, and of course there is plenty of room for the socket wrench of your choice. You'll need a 13mm socket.

The bottom front bolt threw us for a loop. There's enough room to get a 3/8-in. drive wrench down there long enough to get it loosened. You'll need a 15mm socket. It won't take long, however, for you to find that the upper radiator hose interferes with this incredibly long bolt. We switched from a socket wrench to a pair of pliers -- grab and twist, grab and twist. Remember, we're racing against the clock here! It threads for a little while, then enticingly pulls free about an inch, but then it encounters more threads (the alt's other bracket). Grab and twist. Near the end, it helps to have someone bend the upper hose out of the way of the bolt.

...The Alternator Is Out.

With all the bolts out, grab and go, right? Wrong! The tensioner doesn't mess around! Even with no bolts holding it down, the alternator cannot escape until the tensioner lets go of the belt.

Very important step! Note that the instructions in the Haynes manual, and the pulley's instructions, are dead wrong here. When you're trying to release the tensioner, there are two things you need to know. First, the keyway to release the tensioner is to the left of the tensioner pulley. It is not in the center of the pulley! Second, the tensioner keyway accepts a 3/8-in. drive ratchet, NOT a 1/2-in. ratchet per the instructions. All you have to do is insert the ratchet (not a socket -- the ratchet itself) into the keyway and push down. Ta-da, no tension! But, as soon as you remove that serpentine belt, the tensioner's gonna keep your ratchet, so be ready to use your other ratchets for the rest of the job.

Now, if you is us, you have 15 minutes to get to a garage 20 minutes away. But, if you wuz us, you'd also know a shortcut or two and you'd just barely make it. Don't forget the alternator and the new alternator pulley, or your trip is wasted.

The guys who did it for us were Jim, Jay, and Doug at Goodyear Auto Service Center on the Green Bag Road in Morgantown, W.Va. Thanks guys! (No, it doesn't take three mechanics to swap alternator pulleys -- they were just all enthusiastic about the job.) It took them less than a minute.

Back at Paradise Garage, we were faced with the next pulley: the water pump. The water pump pulley is that funny-looking one (it looks like an inside-out pulley) just above the crank. With no tension on the belt, it was free to spin, spin, spin. It's hard to apply force to a spinning pulley.

The pulley is held on by four bolts (1/2 inch -- standard at last!). The first three came off easily: put a 1/2 inch box wrench on one of the bolts, then turn the pump until the wrench bangs up against something -- now you've got something to apply force against. Use a ratchet wrench to remove the other three. But you can't do that with the fourth one.

It's a little hard to tell, but the point of this picture is that the belt doesn't need to be removed. It just sorta flops in its natural pattern.

After much experimentation, here's how we did it. Put a 1/2 inch socket on the last bolt. Now slide a sturdy screwdriver between the socket and the center of the pulley. This creates a fulcrum from which one person holds the pulley steady while the other one gives the ratchet wrench a good yank (the bare steel of the socket will spin nicely against the bare steel of the screwdriver). It's awkward, but it works.

With the water pump pulley out of the way, it's easy to get to the crank pulley. There are four bolts holding this one on, too, and they're also 1/2 inch. The engine provides the counterbalance to your wrenching, so the bolts come right off.

Installation is reverse of removal.

Don't you hate that? So do we. Here we go. The reinstall marathon.

Install the new crank pulley. Make sure you put the correct side in (hold the old against the new, make sure the center plate is in approximately the same place). Torque it down using the same pattern you would on a four-lug wheel.

Install the new water pump pulley, but don't worry about torquing it down yet. Loop the serpentine belt around it in the correct place. What, you weren't paying attention to that? Shame on you. Lucky for you, there's a diagram. Stare confusedly at the engine, leaning on your elbows in front of the latch striker. Now lift your right elbow. There's your diagram.

Put the alternator back in its cradle, bolt it up, and attach the wires. Note that the front lower bolt is as much of a nuisance to get in as it is to get out -- have someone hold the hose back again. Loop the belt around the pulley.

Make sure the belt is squarely positioned over all the pulleys, then get down in there and lift on the tensioner. Reclaim your ratchet.

Double-check the belts.

Torque down the water pump pulley, now that the belt tension is holding it in place.

Torque down every bolt you touched today, one more time. You don't want anything falling off.

Reattach the battery and give the car a quick test-drive! Then check everything again, and if it all checks okay, give the car a thorough shakedown drive, followed by one last check.

All buttoned up. Heck, it even looks stock (hint to those of you in visual-inspection emissions states).

So, did it help performance? The owner of the Mustang claims it feels a little better, but that may be psychological as much as anything. Still, every little bit counts, and this is one more step on the road to serious horsepower. Next stop: headers!

There is a couple of things you should be aware of when installing underdrive pulleys. First and foremost, your alternator will have a harder time keeping up with electrical demand. Megastereos may cause problems, although Ford's own Mach stereo was not affected. You may notice a slight waver in the voltmeter when you're running a lot of accessories, but don't worry about it. Your car won't crap out. Although you may find yourself buying batteries more often than a stock car would.

Also, reduced water pump speed may result in higher engine temperatures in hot climates. It's winter here, so we aren't too worried for now, but a low-temp thermostat is in the works for this spring. Never go lower than 180 degrees, however. The 160 degree thermostats on the market will cause your car to run in warm-up mode constantly, which hurts performance and damages expensive parts.

Hey, with power comes responsibility. But here at Paradise Garage, we'll take that any day.

Things we might have done differently. Had we planned this escapade a little better, there is one change we would have made. Instead of diving straight into the alternator, we should have loosened the water pump pulley first. Why? Because the darn thing is really, really hard to get off without any tension; with the belt still on, the whole engine holds the pulley in place. So make your life easier than ours was. Leave extra time to loosen the water pump pulley first, then go back and take off the alternator.

Also, if we had more time, we would have gone to Sears and bought some Craftsman metric wrenches. Using a vise-grip is a sure way to destroy a nut. We also probably would have bought one of those neato Robo-Grip thingies. The lesson, again, is to plan ahead.