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Under Drive Pulley Guides

Pros and Cons of Getting an Under Drive Pulley

The under drive pulley is probably one of the cheapest and most popular add-ons that you could get for your vehicle today. This particular component has been around since the 1950s and is commonly installed in high-performance hot rods back then. When it comes to upgrades, an under drive pulley will provide one of the best returns for your money because of the amount of performance and horsepower that you'll gain for very little cash spent. Let's check into the pros and cons of getting an under drive pulley and see if it's worth installing one in your ride.


What draws people to getting an under drive pulley is the relative ease of adding horsepower to their vehicles. As much as 15 horsepower can be easily gained from a good under drive pulley kit, depending on the number of accessories your serpentine belt is powering under the hood. You'll also be able to decrease the wear and tear on your serpentine belts. Since the belt makes contact with the pulley guides less frequently as a result of reduced rotation, you'll probably be able to extend the belt's service life way past the manufacturer's specifications. Finally, components such as your bushings, bearings, and other related parts will have an extended service life as well. Because of the decreased clutch rotation, even parts like the AC unit, water pump, and alternator will last longer.


Unfortunately, there are several things that you'll need to look out for when getting an under drive pulley for your vehicle. For instance, your car's battery could drain faster, which can result in underperforming spark plugs, dim headlights, and more. This will become more apparent when you're vehicle is idling in traffic, and since all your pulleys will be running at their lowest RPMs, your alternator might not spin fast enough to power all of your accessories. The same problem can occur with your vehicle's cooling system, particularly with the water pump pulley. At slower speeds, the water pump might not be able to push coolant into the engine fast enough, which could result in overheating.

Weigh it out

For most vehicles, under drive pulleys should not cause any issues at all since most auto manufacturers provide a certain buffer for your vehicle's stock accessories. This means that your car's stock alternator, water pump, and other components that are connected to a belt, should be able to perform just as well with an under drive pulley. Problems should only arise if your ride is using some high-powered components like racing-grade spark plugs or high-powered aftermarket stereo equipment, which will seriously tax your vehicle's alternator.

For most people, they won't find any downside to installing under drive pulleys on their vehicles. With prices ranging from $100 to $250, you can easily find one that'll suit your vehicle and budget and reap the benefits of added power and performance with a simple pulley swap.

Upgrading to an Under Drive Pulley

Most of the components under your car's hood are powered by a series of pulleys, and these are connected to a belt that is driven by your engine's crankshaft. When you alter the size of your pulleys, you could free up some hidden horsepower from your engine, with very little modification to your ride. Let us show you how to install an under drive pulley, one of the most popular aftermarket upgrades on the market today.

Difficulty level: Moderate

What you'll need

  • Floor jack
  • Jack stands
  • Socket set and ratchet
  • Gear puller
  • Under drive pulley

Step 1: Open your vehicle's hood and locate the serpentine belt near the front or side of your car's engine.

Step 2: On older vehicles, you might need to remove certain parts like the air intake hose in order to access your car's serpentine belt. Refer to your car's manual on how to do so.

Step 3: Loosen the bolt on your serpentine belt tensioner to release the tension on your belt so you could take it out easily. Take a note on how it routes over the pulleys so you could reinstall it properly later on.

Step 4: Remove the bolts that hold the stock pulleys in your engine. Depending on the type of pulleys in your car, you may be able to remove them by hand after loosening their bolts or you may need to use a gear puller to take them out.

Step 5: Install the under drive pulley by securing it to the appropriate mounting holes and tightening its bolts according to specification.

Step 6: Reinstall the serpentine belt and tighten the belt tensioner.

Step 7: Make sure that you reinstall any components that you took out before hand.

Step 8: Start your engine and check your pulleys and belt to make sure that they are not rubbing against other parts inside your engine.

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