i've been looking for an underdrive pulley and i believe i've found one. http://www.jdsperformance.com/index....item&inmake=96
what i'd like to know is if anybody else has tried them and what their recommendations are.
is there a better brand or has anybody found a complete set for an '02 3.9.
also, were the gains noticable?

 

well i hear they work very well helps your fuel mileage also i've been thinking of getting one for my truck for quite some time i'm just worried about the alternator slowing because of my sterio the headlights already dim when the bass hits and at 25% reduction i'm afraid its going to get much worse

 

we have UDs on amandas truck, and i believe that they are 25%...it DOES significantly affect the charging system...especially running twin electric fans and the MSD igntion.

 

its not a complete set but summit racing has the same thing for around $50.00+shipping and its rated at -%25 also. beats paying over $250 for one. buy it and tell me if its worth getting one.

 

i have the summit under drive, 400w amp running a pair of 10" subs and a 600w amp running 4 other speakers. i admit i don't have the bass cranked up all the way (it sounds good at about 25% listening to rock) but the lights don't dim, ever. the only "problem" i have is at a stop light idling with the blower on full blast and the stereo maxed; the voltage drops to about 12v instead of 14 and i think it might do that without the under drive (hey someone check that). still theres no noticeable side affects. i gained 2MPG on the freeway, it made a noticeable difference in power and the A/C system blows ice cubes instead of blizzards now. best 50 bucks i spent on the truck yet. remember you need a different belt too

 

Is that the one from summit racing that you have. It looks like they have 2 different mfg. for around $50. One has a crank pulley only and one has a crank and alt. pulley. Ohh and I thought blizzard were cold as well... Are you saying that the blower is at a slower speed now or???

 

Does the alternator pulley correct the 25% loss? If the single crank pulley is 50, why would one pay 200 more for the alternator one if not?

 

no because the A/C pump is turning at a slower speed the air doesnt come out as cold, the blower is unaffected. my point though was that i thought it was too cold to begin with, even on its lowest setting i would freeze on long trips and now its just right. i can still crank it up and freeze too, i guess it just feels more adjustable.

and yea i think when you get the pulley set it compensates the loss on the individual pumps, personally i dont see the need for it

 

i've been thinking about it for a while and for $50 its not a huge deal for the beneifits it gives. but how do find the new size belt. won't the tentioner take care of the extra slack?? i thought it would but mabey not, and how can i explain this to my wife that i need this part when we are trying to buy a house??? and finally, why when i ask my wife if she wants to race, she says race what??? she drives a ford focus zx5, auto.
after you get it set up post a "how to" because i've always been hesitant to mess with the belts.... thanks..

 

do what i did. "honey this is going to make the gas mileage on the truck a lot better" and the underdrive instructions came with the belt size i needed in the instructions. obviously it may be different for different years or size motors. the whole thing took like 20 min to install requiring only a socket set and a 6" extension.