Thread: added UD pulley's, need to change anything?
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Old Wed, June 17th, 2009, 01:00 AM
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Jackpine Jackpine is offline
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Quote:
Originally Posted by Sburn View Post
So, you're suggesting I might hook a fish scale up to the fan with the engine stopped and measure the drag as torque, right? That could be good to know. Not sure about 2008+, but my 2007 does have some drag when stopped, so whatever scheme the clutch is, it's not perfect.
I thought you said the change was in the 2008 MY. My 2005 certainly has viscous drag when I attempt to spin it by hand with the engine stopped. I haven't actually tried this, but as I understand it, the drag should be greater if the engine is hot. (I'll have to give it a try). In my engine, the fan ALWAYS turns, but, it is supposed to turn faster (closer to engine speed) with the engine hot. (I know you know this, I'm just adding it for anybody who may not understand how a viscous clutch works).

I doubt you could measure it with a fish scale though on a stopped engine. You'd need to catch the fan to a scale mounted on a rafter or something and measure the force on the stalled fan with the engine running. Then, you could calculate the torque/hp loss from this force and the distance you had the "hook" from the hub. It's not something I'd like to try, since it sounds a bit dangerous.

But, if there is NO resistance in the 2008+ line, then that is a whole different clutch! And, you should be able to compare the relative resistances in different MY trucks by feel.

- Jack