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Underdrive Pulley?

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Do they make an underdrive pulley for the 6.0l truck motor? if so where can i get it? and will it work for a l92/l76 swap? thanks in advance.



yeah they make one, but from what I hear, they're no good for the money, as in very minimal power. You should spend your money on something that will get better gains, but if you really want it, here's a link.

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my friend has had zero problems with ASP pulley, for each his own though



underdrive pulleys slow down your accesories. if you are doing a blower look into an overdrive pulley, it will help you run a larger supercharger pulley to help with air intake temps. IMO

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i've used the asp underdrive for around 30,000 miles on my truck and have had no problems. I gained 1 tenth at the track with it, so if you buy it used it'll be worth it, new i would spend the money on something else. If you do it make sure to buy a new crank bolt as they are junk after you take them out.

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  • 4 months later...

I know its an older thread but I'm looking into doing a few mods here soon. I'm going to install some pacesetters lt's I have, install cat-back proable gmpp, tune not sure who yet. I'm debating on a cam.

Are the underdrive pulleys a waste of $? from What I'm reading it sounds like it. any other mods that will not break the bank?

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i will say this they will help the trucks less than the cars. i recently put an asp 25% ud on my ls1 camaro and i noticed a difference from sotp anyway. it revs faster for sure and i can spin my tired in 1st , 2nd and some of third gear. my car is a manual 6 speed with all bolt ons and stock internals. its putting near 350 rwhp .


on a truck being much heavier it will see less gains .


but rule of thumb for the ls1 cars is about 1 tenth at the track and 7 rwhp .


if your goal is bolt ons only it wont hurt you but dont expect anything significant. you may have some problems with your a/c being it will spin your clutch fan ( 03-04) a bit slower so youll need more airflow. it should be able to keep up with power demands but i did a higher amp alt at the same time since i have a 500 watt stereo in the camaro. i will get to 13.0 volts when the a/c is on and the e fans are on idling at 800 rpms.


for a heads and cam or cam only swap id probably do one just becasue youl lhave the crank pulley off.


i also got to make me a crank pulley install tool that kicks ass. all thread, some thick pipe and a few nuts and washers.

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