Help: Old tensioner vs. New tensioner

[jnaut]

I'm swapping out my old tensioner for the new Dayco model, and I noticed that the new idler pulley is considerably larger than the old one.

Simply put, what gives?

Should I be concerned I got the wrong one?

Experts, what say you?

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[ptsb5a]

Shouldn't be a problem at all. A slight change in the overall diameter of one single pulley shouldn't change the length that the belt has to cover all that much. It is the tensioner afterall, it just won't need as much tension to keep the belt snug.

 

[offrovering]

it will be fine, the tensioner is a self adjusting type

 

[jnaut]

Kay, thanks. The gap between the engine crank pulley and the idler pully is teeny weeny, now. Plus the gap in the tensioner where you measure for belt-stretch is changed significantly. But it is what it is. I've installed it and it all works fine.

 

[ShafferNY]

Just a guess. By making the pulley as large as possible, it allows the tensioner to spin the minimum number of rotations possible, thus extending the life of the bearing. Or it could simply be that the pulley fitted to the tension also fits many other applications, thus cutting down on production costs.

As said, don't worry about it. A lot of aftermarket parts aren't necessarily identical to their OEM counterparts.

 

[Auberon]

I'm with you. Considerably less revs with that difference in O.D. gone. Load might be a good deal more even and arc of contact will also be better (even though it isn't a driver) now as the PCD of each pulley is a lot closer. The whole thing should be more stable (I would think).
Auberon

 

[tjkj2002]

The one larger pulley on the aftermarket tensioner for the 3.7 is due to the fact there is 3 different belt lengths for the 3.7 in various vehicles,and it works on the 4.7's as well.

 

[Uncle Krusty]

When the bearing in the smooth pulley started whining, I decided to replace both it and the ribbed one as well. The problem I ran into was that while everyone listed and stocked the smooth pully, no one stocked (some did not even list) the ribbed one.

At the fourth place I stopped, after failing again to even list the ribbed pulley, one of the more experienced clerks took it and disappeared into the back. About 5 min later he reappeared with a match. He had gone back and started going though boxes until he found the right one.

I never found out what applications the new ribbed pulley was listed for, but like he said, many manufactures use the same ones.

It was all for nothing as three months later, the tensioner broke, an I ended up buing a new one - that of course - only came with new pulleys. At least now I have a couple "low mileage" spares.