I am finishing up a front end rebuild on my 99 F150 and I have a question.

How can you tell what bolt pattern you should have on your Idler arm? I know there are two patterns, but how can I figure out which mine is without measuring it. There has to be a reason for the difference.

My truck is a '99 F150, Regular cab, Short bed, 4.6L, 4X4.

I don't have a garage of my own or I would just crawl back under and measure it up but, it's 10 degrees outside. Any help would be appreciated!

 

Thanks for all the responses! Oh wait...

Anyway, I went to yet another dealer on my lunch break and seem to have gotten the most definitive answer I will get.

It is essentially random. The tech I spoke with told me that he has done several dozen idler arm replacements on the PN96 F-150's and he has only ever seen one with the longer bolt pattern. Beyond that he didn't see any noticable difference in configuration between that one truck, and many others he had done.

In conclusion... who the hell knows? I got the shorter pattern and it fit.

Take it easy!