# 2006 GTO Pulleys



## Tuefelhunden (Jan 5, 2012)

I have a '06 GTO, I'm looking at changing the balancer pulley and the alternator pulley. I notice when checking out parts that there is an overdrive and underdrive pulley. The questions I have is what is the difference between the overdrive and underdrive? Do I or should I replace both/one/none?


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## 87GN06GTO07IRL (Aug 10, 2009)

Underdrive will be smaller, lighter, free up power, and spin slower. Overdrive will do the opposite.


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## Tuefelhunden (Jan 5, 2012)

Sorry if I'm repeating myself. There is a lot I don't know and I'm trying to learn. There is an underdrive balancer pulley, overdrive alternator pulley and an underdrive alternator pulley. So do I only want to replace the two underdrive pulleys?


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## HP11 (Apr 11, 2009)

If I'm understanding this correctly, and you're trying to get back to stock, you'd have to change all three.


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## Tuefelhunden (Jan 5, 2012)

No, stock is what I'm trying to get away from. I'm going for performance.


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## HP11 (Apr 11, 2009)

You'll get argument on both sides of this but, IMO, underdrive/overdrive pulleys don't do much for performance.


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## pocketmaster (Feb 26, 2010)

HP11 said:


> You'll get argument on both sides of this but, IMO, underdrive/overdrive pulleys don't do much for performance.


I have heard the same thing. What little gain you get, if any, is not noticeable.


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## 87GN06GTO07IRL (Aug 10, 2009)

Grab a lightwieght underdrive balancer and be done. ati makes great ones. Taking rotating weight off the crank is always a good thing. Less stress on the bearings too.


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## billyjack2 (Oct 21, 2011)

A underdrive pulley will increase performance.... to what extent I am not sure. You are, however, reducing rotating inertia through gearing and reducing losses in pumps. Another affect is that you will not be overspeeding the stock accessories as they are designed to work at low rpm with very limited exposure to high rpm.


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## jpalamar (Jul 22, 2008)

If your taking the OEM ones off for a service, I'd upgrade them. I wouldn't waste my time or money on doing this as a stand alone mod though.


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## HP11 (Apr 11, 2009)

Your advice probably won't reach the OP. He hasn't been back since Jan. 9 like so many of them seem to do. Maybe the answers up to then were sufficient.....


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