Well OK... and thanks a Lot...
I'm was afraid, I'm going mad allready...
Yes, there never was a problem with the Routing... just the Pulley makes no sence...
In Germany, we are only a few Rangers, so everyone makes the best he can.
But I'm surprises, that in America with soo much Rangers nobody asked about that part and why the Replacement is grooved...
Well... YOU can go to NAPA or Rockauto, lay the old Pulley on the Table and say: "Give me a new one, please"...
Here shipping with USPS is the triple Value of that Pulley...
I was at my Parts-Store yesterday, and he'll look for me, if he can get a smooth wheel.
Yes, we discussed here, too, if the grooves could be for cooling or silence.
But I'm afraid, when I'm wrong, and the Belt rips, I wan't get help from ADAC (That's Drivers-Service Club, I think like AAA in the US).
OK, we got it... maybe someone knows the original Motorcraft Replacement No. of that wheel ? I think Motorcraft YS-180 looks fine... Gates 38012 looks also, like it could work...
If anyone replaced this Idler with a smooth one, or knows, why a grooved Pulley is listed and sold today, maybe we get a little wiser...
I wrote to Ford.com... maybe they know about this. Unfortunally it's not easy to call them... can't get 0800 Numbers in the US.
But I very lucky

not to be alone with this question.
Thanks for your help...
Tom