F150 makes a high pitched squeal on deceleration

[GVS]

I have a 2006 F150 with 170 hours and when I slow down quickly from a normal cruise speed and come off plane the motor makes a high pitched squeal for a 2-3 seconds. It does not make the noise if I gradually slow down, only when I slow down quickly. It sounds similar to a bad alternator bearing on a car (which is a constant sound) or even a squealing belt on a car. There is no noise at idle or upon acceleration to a planning speed, so I don't think it is the balancer, but I could be wrong. I have read some posts about a shaft bushing problem, but it seems if that were the problem, it would be a constant noise. Any ideas? Thanks

 

[deepsea21]

Just guessing but squeals have been attributed to low gear case oil. Is is fully filled?