i put a summit underdrive damper pulley on my 06 trx and it helped the high end, but i drive it like i stole it. if you spend a lot of time in the low end of the power band u wont notice it as much. u can also tell the engine revs smoother with the pulley because its also a damper . have a legit mechanic put it on with the right tools. this is my third underdrive pulley i have installed on my cars, s10, stratus rt, and now my hemi, and i could tell the difference each time. also unless your running a high output stereo or are sitting in los angeles traffic for 4 hours stop and go u wont notice less charge. u will notice your ac is alittle less cool. my most honest answer .

 

I don't have any knowledge of underdrive pulleys on a Hemi. However, I spend a lot of time on a 300M forum and a lot of those guys put 'em on their 300Ms. Nobody complains about the AC or alternator output. I know at least one guy who dyno'd before and after the underdrive pulley, and he really did see a HP and torque increase.

 

some of you worry way to much about the pulley I put underdrive pulley's on my GT mustang and never noticed a problem at all with A/C alternator or even battery and I was also running a 2000watt sound system without ever having a problem and it gave a nice pull in the top end and I plan on adding a set to the hemi

 

so the pully only effects the top end eh? ... no use of me putting on my dodge lol..