Is the idler pulley necessary on a 4.0?

Did you seriously notch 80% of the frame away so that the drag link end would clear with your fancy billet pitman arm?

 

Maybe... yes.
It’s very sturdy though.
Had to cut and flip the pitman arm to keep it low enough so it wouldn’t hit my leafs.
Has 3/8 bar welded inside the frame and plated on both sides.

 

OK, looks a lot stronger than your previous pic.

 

Looks very nice to me !

 

Think about the direction all that stuff turns then consider how much power it takes to turn the compressor on a nice warm day. The belt turns the entire mess no belt your are dead in the woods. 3.1416 you figure out how much surface you'll miss. If it ain't broke don't fix it.

 

Maybe a mechanical engineer can weigh in but belt friction is a function of angle of contact along with coefficient of friction.



To me this looks like a fairly significant reduction in tension, 20° (~0.35 radian) maybe? It would be on both the crank pulley and A/C, it's possible the idler is for either or both to get sufficient tension.

 

I’ve remove my ac due to malfonction, then removed this pulley, but if you run your ac dont remove it

 

I would approach this in two ways, the first is what you've already considered: delete the pulley. As was said this will provide much less contact area on the A/C pulley, but will that actually cause belt slip? Without more numbers it would be hard to say. Toyota ran the numbers though and thought they needed more coverage. That said, why did they think they needed more coverage? In many cases Toyota has a higher factor of safety and/or life expectancy than most of the modifications people do to their trucks. There's a reasonable chance it will work fine but for not as long.

For this, I'd do it experimentally: get a shorter belt, remove the pulley and see if you get belt slip when the A/C is on in various conditions (hot, cold, wet, dry). If not, run it for a while and do the same thing. The friction coefficient will drop as the belt wears.

My second method would be to do the opposite, and that is make a bracket that moves the idler pulley higher. You may or may not need a smaller pulley (which would mean increased bearing speed/wear), but it would provide extra wrap around both the crankshaft and the compressor pulley. This would be my prefered method, especially if you can do it without reducing the size of the pulley bearing.

Jeff