Finally the correct accessory belt

[dieselwezel]

For the longest time i couldn't get a correct accessory belt.
I owned this truck for over 10 years and had this truck not driven most of that time so now i wanted to replace this aswell.
Turns out that the belt tensioner has a grooved and smooth pulley and i thought this was correct but it and the bracket belongs to 2000, 7.3
Not sure why this was changed but atleast i know now what belt to ask for.

[madpogue]

Semi-common upgrade for the OBS; there's a TSB about it. The two-pulley tensioner replaces both the original tensioner and the grooved idler next to it. So the number of pulleys is the same.

[Baileysbees]

What would be the up-grade if it still has the same amount of pulleys?

[dieselwezel]

it does have one more extra pulley,alot of hassle to go thru because the brackets dont interchange with each tensioner. thought there had to be a reason for the mod that i am not getting.

[Patrick Feeley]

Originally there were problems with the single-pulley tensioners failing. They went to the dual-pulley tensioner to help solve that problem. On an OBS, the mount needed yo be modified for the dual-pulley tensioner. I'll see if I can find the copy of the TSB. Cheers!

[madpogue]

If you wind up the two tensioners, it's easier to see why. The early tensioner only swings the one pulley, of course, so the force on it is offset from the pivot point. Over time, the spring (or maybe it's the tensioner body itself) wears in such a way that as it unwinds and tensions the belt, it's angled wrt the other pulleys. The SD tensioner has the pivot point between the two pulleys, so the force on the spring is equal betwen the two pulleys, and the pivoting action tends to remain in a straight line.

Here's what I mean about the OE tensioner as it wears. See how the angle changes as I wind/unwind it?

tensioner - YouTube

tensioner - YouTube

[dieselwezel]

that makes alot of sense,i imagine theres alot of stress on the drivebelts with the 7.3 and like you say with the extra pulley it kinda divides the load out. For a TSB i dont know why any of the ford dealerships or napa couldnt take notice. asked many times if the truck was an ambulance package which i knew it wasnt,and even then that belt was way too long.

[Baileysbees]

So how may OBS have done this mod/upgrade with better results than stock? As one might see in a post I had a problem with my pulleys over the weekend. So at this point I am think of all of my choices!