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Quick Drive Belt Riding to one side

J
Jan 21, 2016
49
9
8
Dillon, CO
Does your QD belt ride to one side of the gears like in the picture below? Ever since I did some tunnel repairs the belt seems to ride towards the inside edge. It isn't touching the brake rotor yet but its pretty much riding on the inside flange of the lower pulley. Its the original belt (2013 with 700 miles), and it probably has 250 miles with the belt riding like that. I just installed a turbo on the sled and I'm having night terrors that the belt is going to break on me.
 

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A

ak

Well-known member
Dec 7, 2007
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723
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Does your QD belt ride to one side of the gears like in the picture below? Ever since I did some tunnel repairs the belt seems to ride towards the inside edge. It isn't touching the brake rotor yet but its pretty much riding on the inside flange of the lower pulley. Its the original belt (2013 with 700 miles), and it probably has 250 miles with the belt riding like that. I just installed a turbo on the sled and I'm having night terrors that the belt is going to break on me.

Mine don't but I would be checking your jack shaft bearing for any wear are something could be bent.
 

diamonddave

Chilly’s Mentor
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Apr 5, 2006
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Wokeville, WA.
Yeah something looks wrong with that picture. I'd start micing stuff and double checking washers, thicknesses of everything.
 
J
Jan 21, 2016
49
9
8
Dillon, CO
Yeah something looks wrong with that picture. I'd start micing stuff and double checking washers, thicknesses of everything.

Yeah it seems off to me too. I ended up buckling the tunnel by the foot well the year before last. I fixed it by beating the tunnel straight and installing CrMo braces from Van Amburg. I'm wondering if the jackshaft is slightly higher on the right hand side making the belt walk down to the low side. I don't think there are any spacers in the setup if I remember correctly. I was really hoping someone would chime in a say "mine is like that too" lol. I guess I'll look it over one more time and if I can't figure it out I'll run it till it breaks.
 

LoudHandle

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Apr 21, 2011
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Valdez, AK
If either bearing was bad on the right side the belt would be running to the outside. I suspect the tunnel damage was to the left side foot well? And while it may be visually close to straight, the dents have shortened the center to center distance on that side. Any belt drive is far more sensitive to any misalignment than a chain setup (primarily due to the width of the belt, but also because of zero stretch / flex).

You can run it that way. Just know that it's not right, and both performance and life will suffer. As well as extra heat generation from the belt being forced into the flange and having to always slide axially as it rotates around the sprockets.
 
J
Jan 21, 2016
49
9
8
Dillon, CO
If either bearing was bad on the right side the belt would be running to the outside. I suspect the tunnel damage was to the left side foot well? And while it may be visually close to straight, the dents have shortened the center to center distance on that side. Any belt drive is far more sensitive to any misalignment than a chain setup (primarily due to the width of the belt, but also because of zero stretch / flex).

You can run it that way. Just know that it's not right, and both performance and life will suffer. As well as extra heat generation from the belt being forced into the flange and having to always slide axially as it rotates around the sprockets.

You are correct it was the LH side. I would agree with you on the dents but I replaced the tunnel reinforcement overlay with a steel one. The bearing carriers for the jack shaft and the drive shaft both mount to the steel plate that is riveted to the thin side plate of the tunnel. So unless the steel yielded to the aluminium when I riveted them down, or the plate cutout is slightly off, the center distance should be spot on. I'm wondering if the drive shaft axis isn't perpendicular to the tunnel on one side or the other. I'm scratching my head how to measure that.
 
G

geo

Well-known member
Dec 1, 2007
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Kamloops B.C.
Easy to do with machined pulley's (quality straight edge off top pulley, 4 measurements off bottom pulley, move other end of track shaft to square up). Hard to do with stock pulleys. Even being out a few thou. with center to center on the shaft ends on either side will have the belt walking.
As Loudhandle said, the width and rigidity of the belt requires tighter tolerance.

There are some things to check. I did some long winded posts in '13 '14 and '15 describing as best I could in words if you want some reading.
First thing is if the QD plate was glued on square to the tunnel (see if the jack shaft shoulder and plate have clearance before torquing on the top pully, push in on the top and see how much it flexes until touching, shimming if needed).
The other is the parallel shafts you are thinking about. You can adjust this by moving the opposite side of the track shaft (loosen the 3 bolts and jiggle around is sometimes enough, sometimes requires a bit of carving on the tunnel holes, once centered a couple of well placed rivets will be your final alignment spec for future work).

First thing is to find out is if the belt walks over to the other side of the pulley when run in reverse (to eliminate a funny worn belt possibility). If that is the case then you can fix with the above.
You can also use this as a-long-way-around alignment checking tool if needed.
 
Last edited:
J
Jan 21, 2016
49
9
8
Dillon, CO
Easy to do with machined pulley's (quality straight edge off top pulley, 4 measurements off bottom pulley, move other end of track shaft to square up). Hard to do with stock pulleys. Even being out a few thou. with center to center on the shaft ends on either side will have the belt walking.
As Loudhandle said, the width and rigidity of the belt requires tighter tolerance.

There are some things to check. I did some long winded posts in '13 '14 and '15 describing as best I could in words if you want some reading.
First thing is if the QD plate was glued on square to the tunnel (see if the jack shaft shoulder and plate have clearance before torquing on the top pully, push in on the top and see how much it flexes until touching, shimming if needed).
The other is the parallel shafts you are thinking about. You can adjust this by moving the opposite side of the track shaft (loosen the 3 bolts and jiggle around is sometimes enough, sometimes requires a bit of carving on the tunnel holes, once centered a couple of well placed rivets will be your final alignment spec for future work).

First thing is to find out is if the belt walks over to the other side of the pulley when run in reverse (to eliminate a funny worn belt possibility). If that is the case then you can fix with the above.
You can also use this as a-long-way-around alignment checking tool if needed.

Thanks Geo! That gives me an idea of some things to check. I did remove and re-bond the QD bearing plate on the sled. I will check it to make sure its straight on the tunnel. Maybe if I'm lucky I can just adjust the jack shaft at the clutch side and get things back in line running true. I didn't really consider the belt drive when I tore into the tunnel to repair it. I'm sure they use some pretty accurate jigs at the factory when they assemble these things. I guess worst case I could convert to a chain case, but that seems like a lot of work too.
 
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