Belt slipping after mgw install

[mig4236]

Just installed the mgw shifter on my 07 shelby and for some reason now my belt,(I think its the belt) screeches loud when I shift fast. Never did it before.When I shift slow and normal its fine. Replaced the belt a month ago with a GATES K100840 84.625. Can it be my tensioner or the belt?
Here is the mods

2.3 FRPP TVS with 2.6
90mm idler
Ford Racing 65MM Throttle body
JLT 127mm CAI
Dyno 648

 

[BROK3N-SVT]

Mine makes the noise too but I don't think it's the belt. I think I read somewhere that when you come out of boost after a hard pull, the bypass valve opens up and the air that blows through makes the noise. Not sure how true it is, but it would make sense. My belt is very tight and I doubt it's slipping.

 

[Stri8ed]

This is a guess and I could be completely wrong, but now that you are able to shift harder at a higher RPM, maybe the force at which it engages is enough cause a chirp when the tension comes back on the belt, after a high RPM shift. My belt chirped on my blown 2010 in between hard shifts when it reengaged.

 

[mig4236]

Mine makes the noise too but I don't think it's the belt. I think I read somewhere that when you come out of boost after a hard pull, the bypass valve opens up and the air that blows through makes the noise. Not sure how true it is, but it would make sense. My belt is very tight and I doubt it's slipping.

I had a friend check it out while having the hood opened and verified that it is the belt that slips when i shift fast. So dont think its the boost issue. I dont have to be boosting to make that noise.

 

[mig4236]

This is a guess and I could be completely wrong, but now that you are able to shift harder at a higher RPM, maybe the force at which it engages is enough cause a chirp when the tension comes back on the belt, after a high RPM shift. My belt chirped on my blown 2010 in between hard shifts when it reengaged.

I thought so too but even at low rpm's it screeches. No boosting. Just shifting fast.

 

[stkjock]

stock tensioner?

how many miles on the car?

 

[mig4236]

stock tensioner?

how many miles on the car?

Yea stock tensioner and has around 26k miles

 

[Ninjak]

That may be it. I have aftermarket tensioner...zero slip on a 2.4 pulley.

 

[stkjock]

Yea stock tensioner and has around 26k miles

it's possible that the spring in the unit is no longer strong enough. IIRC it can be replaced, but certainly, if you are going to up the boost and shorten the belt, an upgrade would be beneficial IMO.

 

[19COBRA93]

Definitely sounds like belt slip. Possibly run a slightly shorter belt, or add an aux idler. I ran a 15% lower/2.70" upper combo on my 2.9L with a stock tensioner, and once I added the aux idler I had zero belt slip issues.

 

[rlhay2]

I had a friend check it out while having the hood opened and verified that it is the belt that slips when i shift fast.

How did you manage this? Was this on a dyno? If not a dyno, how?

 

[mig4236]

How did you manage this? Was this on a dyno? If not a dyno, how?

No dyno. I just have to drive a little like 2-5 mph then shift real fast for the noise to occur while he's standing next to the car. He told me that the belt stops or slips when I shifted.

 

[gr850]

I had a friend check it out while having the hood opened and verified that it is the belt that slips when i shift fast. So dont think its the boost issue. I dont have to be boosting to make that noise.

Your friend is in better shape than mine.