Serpentine belt

[BugZapr]

04 SRT 10- noticed frayed belt - installed new one ( 7 rib belt ) - in 2 days the outboard 2 ribs blew off. Noticed the tensioner was out of alignment- put on new one- same problem. Put old belt and tensioner back on.
Car works fine on 5 rib belt. The 5 belt ribs sit on the inboard 5 ribs of all but the tensioner , where the 5 belt ribs sit in the outboard 5 ribs. This is a serious alignment issue ( about 1/4 inch ! ) - even when replacing with factory parts. I’d like to run the proper spec belt. Dodge has been completely unhelpful in resolving this issue. Anyone else experience this and have a solution ?

 

[MoparMap]

That's pretty bizarre. Have you done anything to the car? I've had my belt on and off more times than I can count while dealing with my power steering and have never had an issue. Modern serpentines rarely seem to have issues. Sounds like something isn't where it's supposed to be though. Have you checked your crank pulley? I know the 03s and early 04s had an issue with the bolt losing tension and backing out, maybe the pulley has moved forward slightly if that's the case? They are still pressed on, so it would be tough, but not impossible. Just one thing to check that comes to mind.

 

[BugZapr]

The vehicle is stock.
All the other pulleys (including the crank)
are in perfect alignment with each other.
It’s the tensioner that doesn’t align.
I even purchased a new one and installed it but it’s exactly the same- out about 1/4 inch.
I’d expect that all the blocks are cast the same ? and the tensioner mounting brackets are cast the same ? ……so they should fit!
But on my car they do not.

 

[MoparMap]

The only thing I can think of with that is the tensioner has a nub that sticks out that is supposed to sit in a notch on the front cover to keep it from rotating. I would assume that would be easy to tell if it wasn't sitting right though as it would probably not just be offset but probably even crooked. I'm not sure how you would tighten the nut on the back of the tensioner either since I think that nub is an anti-rotation feature for that reason as well. On the picture is looks like it's fairly well seated, but that's right at the edge of the shot, so harder to tell. I might have a spare one that I stripped some threads on I could try to measure, plus I have my engine in pieces at the moment, so could measure the one on it pretty easy for reference as well.

 

[BugZapr]

The anti rotation nub fits properly into the
Block ( both the factory one and the new one ). In fact - I have included a diagram which illustrates that the tensioner actually sits too close to the block relative to the other pulleys.