Lens autofocus work using liveview / not viewfinder. Tried two different cameras (EFS 18-55mm Lens)

[ingallspw]

I have an issue with Auto Focusing on my EFS 18-55mm Lens.  It will autofocus using the LCD liveView screen but not the optical viewfinder.  I'll try not to blab so...

• Mechanically works perfectly (No odd noises, broken gears, etc)
• Tried two different camera bodies - Same result
• Reset all settings in cameras
• Updated firmware
• Cleaned lense, mirror, electrical contacts, etc.
• Image looks crystal clear using manual focus
• Again, autofocus works using view finder
• Other lenses work as expected on both camera bodies
• Image stabilizer on / off has no effect
• Cussing, crying, and other forms of a bad attitude have no effect either.

Any suggestions, ideas, fixes would be most appreciated!!!

[ingallspw]

The bank is not very big so I just went and purchased an identical used lens.

Plus here is the fun part!!

After disassembling the lens and noticing the aperture was screwed up more than Channel 4 in a thunderstorm, I tried to put all the little fins back in place but one is warped and bent so just as an experiment, i just took out all the fins and put it all back together.

I was not sure what would happen but at this point... lets go for it right!?  Anyway, to my surprise, the lens works pretty well!  The autofocus works again and the communication error is gone.  I don't quite get the same depth of field but for now, its a decent emergency backup lens!  I've tried just searching to see if anyone was selling just the aperature's "little black thingy's" (leafs, blades, fins, shutters, or what ever they are called) but so far no luck. 

Thank you to all who replied and for all your suggestions!

[ebiggs1]

"I don't quite get the same depth of field ..."

That's because the lens calibration is off.