hey guys got some questions about the engine fans you guys are running down south?? warmer climate than us canadians one truck we have is a 2005 putz 36m z the fan cycles like constantly on warm days like on off on off drives me nuts its so noisy when your pumping. now the 2007 alliance 37m RF it can be 35 c out humid and pumping hard and the fan never comes on. now from what ive noticed with this truck is standing beside the truck you can feel the fan blowing air off the motor. mean while the putz you look at the fan and its turning slowly when its not engaged mean while the alliance turns fast enough to make a good wind when its not engaged also. so am i looking at two diffrent fan clutches as far by looking at both they are horton air driven fan clutches but why does the one have more friction when its not engaged 

there are upgrades to a quieter fan , i'll get part #s

mack# 2 speed 40mh447m

horton # 999 947

fan blade # 2mh466m

main tensioner 87gb45c

main belt 88gb458pggg

have your truck vin # available just in case , most mack dealers will not know about this.

The clutch fan that was in our 2006 Mack Putz was so loud it violated the noise ordinaces and noise standards. Putz sent us a newer updated one for free that was quieter but still fairly loud.

Mack has an upgraded hub assembly it's called a 2 stage fan hub, it still has the horton air shifted clutch but also has a housing that runs off EDDY Current to have drag to turn the fan. A black colored fan is also a lot quieter than the pale colored fan. Horton part number 999947 drive master fan drive. I have them in my pumps and they are awesome.