I've been spedning some time (and money) on my truck lately, and have got it running really smooth - but there is a noise if I accelerate hard, when it changes up gears. The noise sounds like the serpentine slips just at the point of the gear change. I replaced the belt with a new one, and checked the tensioner, and it seemed ok, and I just thought that maybe the old belt had gone hard or something...........it's no different with the new belt? It's doesn't seem to do it any other time, just if you accelerate more than half throttle. It's on a 2003 Expedition 5.4 (2v) 4x4

Has anyone had a similar problem??

 

Is the noise a squeek? I have a squeek after it shifts gear with WOT. Ive been told it could be the fan, but idk....

 

Yes, it's a squeek/squeel! only when shifting gear when I'm 3/4 throttle or more. I asked a mechanic to have a look today, and they said the belt is good and fitted properly - they said they thought that it would have been a siezed fan - but with the engine off they could spin it round freely = they did say it seemed to free??? and that they thought it should have some resistance and maybe should be oil filled and its leaked out???

 

Change the belt to a gatorback. My truck does the same thing I have a new autozone belt and as soon as I get around to it I'll get a gatorback.

 

Yea. At 3/4 throttle, the engine spins soo fast, that the fan cant really keep up, and when it shifts gear, the fan stays spinning that same 5000 RPM or so and it makes a squeek at it slows down..