Deannostang

Very true on the increased longevity of your accessories. Less rpm's throughout their lifetime will definitely increase their overall life. On the subject of a new serpentine belt, unless you have very little miles on you car when you install your underdrive pulleys, I would definitely recommend also installing a new "Ford" belt. Why not? If your belt goes, the car stops. If you have any uneven wear at all on the original belt, you will just be tranferring over that uneven operation to your new pulleys. I don't think you would really like to do that. The standard size belt works just fine as the overall distance travelled by the belt is the same as the stock pulleys. DO NOT SCREW AROUND WITH AFTERMARKET BELTS! I can not stress this enough. With all the Ford products I had owned in the past, the useful life of my OEM belt was around 60,000 miles. Once, and I stress ONCE, I allowed a garage to install an aftermarket belt (NAPA). That belt lasted a grand total of 18,000 miles (junk!). Just a little difference, huh? Ford parts are generally very good. Their oil filters always score high as one of the best available on the market and can be used for extended oil changes, ie: synthetic oil. That is why they refer to their filters as "long life".

The bottom line is I suppose any given dealer can make some kind of stink if they want to regarding non-standard parts installed on your Mustang. Some may make a big deal of it and others may not say anything at all. They DO, however, constantly receive all kinds of tech bulletins regarding existing known problems with many aftermarket products so Ford mechanics can keep a watchful eye out for these particular situations. Not all aftermarket parts are created equal. My local dealer's tuner technician showed me on his laptop (kinda cool mechanics now have laptops on their benches) the official Ford bulletin regarding K&N type "oiled" filters. I had just puked up a couple of bad O2 sensors and he was explaining some of the known causes. Over oiled K&N's that allow leakage of the oil medium through the intake system is a known cause of massive sensor failure. It contaminates the MAF to the point where it definitely needs to be at the very least cleaned (wire sensors) or replaced altogether. It ALSO can contaminate your O2 sensors so they will cease to operate effectively. That is just one such bulletin. AND, that is why many dealer mechanics and service managers are gun shy of aftermarket products.

The hell with it all. Just put on the underdrive pulleys and enjoy! I do and so do thousands of Mustang owners across the country. They definitely work well.

josh_0351

Good scoop, Deanno! [sm=smiley20.gif]

badass04gt

Does the belt size change if you put underdrive pulleys on? If so does anyone know the size?

stanglover03

Thanks Deanno. I only have 22k miles on my car so I dont think I need to change the belt. But thanks for your input.

Deannostang

As mentioned above, same belt size for your underdrive pulleys. The total travelled distance is the same. The stock large pulleys are small on the underdrives and the stock small pulleys are large on the underdrives. Same overall circumference.

jishead

I have Steeda non-piggyback UDPs. Probably put like 10,000 miles on them so far. Love them. Have driven them in scorching St. Louis rush hour traffic bumper to bumper 2 hour round trip commute with no A/C, electrical, H20 probs. Have redlined them a number of times including dyno. No probs. Did replace the belt to accomodate size change. Highly recommend. I would say that any tiny damage created by the UDP would be compensated by the crank swinging less mass and drag but then you'll just drive your Stang harder and compensate and the bottom line is your engine will give up when it's time has come. I never did worry about my warranty since I bought this '02 used with 2,700 miles on it during late 2004. Not even sure what the warranty is!