High pitch sound when towing

[TK42one]

Does anyone know what this sound could be. If you turn it up you can hear a “whine” when pressing gas. Did not do this until towing. 3800# trailer so well within the capacity.

https://391dave.smugmug.com/Grenadier/i-DcSsHnm

 

[Tom D]

Probably turbo whistle. Have you got the RAI?

 

[TK42one]

I do, it sounds like it’s more behind me though

 

[TK42one]

It will be interesting to see if it’s there when I unhook tonight.

 

[Tom D]

When towing you get higher boost pressure at lower revs because the engine is working harder, you’ll hear more whistle at lower revs because the engine is quieter.

 

[Greasemonkey]

I've had a similar noise coming from the front of the transmission for more or less the first couple of weeks. It sounds like a faulty bearing. At first it only occurred when I was driving up a steep hill. Now it also occurs sporadically on flat roads. As soon as the automatic transmission shifts up into 6th gear the noise disappears. It also varies in volume. Sometimes it's very quiet in the background, sometimes it's very loud. I've tried everything but can't locate it. A camera underneath the vehicle didn't produce any results either. The dealer keeps putting me off. Unfortunately there isn't a hill in the dealership area steep enough to cause the noise