I have a 08 H3 Alpha,18,000 kms,that started to make a weird vibration sound at idle,when in gear, forward or reverse,and the engine is at running temp.It never makes this sound when cold,and only when idleing.It sounds like its comming from the front,somewhere,but I can not pin point it.When its making the vibration sound and I put the truck in neutral,the sound goes right away.Its not a very loud vibration sound,its just bugging me that I cant find whats causing it.Any info will be greatly appreciated !

 

Might check the shields underneath the truck. If they get bent slightly or loose they start to vibrate and rattle some. If you have UCP check it also.

 

Pretty sure you have the same issue I had with my '08 Alpha. Took it in to the dealer, and they said there was a bulletin on this. They used nylon tie straps to cinch the heater hoses together (nothing but the best 'high tech' for us). Apparently at a certain rpm, it sets up a resonance vibration in the hoses, that echos through the firewall. This worked fine for about 5 months, then it started again. I determined that the heat from the heater hose, softened the tie straps, they stretched, and the problem was back. I took a 3" piece of foam, water pipe insulation (sold at Home Depot, ect. for your house pipes), wrapped around 1 water hose just forward of the oil fill cap, then used a couple of heavy duty nylon tie straps to cinch the 2 hoses together. I use another tie strap to cinch the hoses, just forward of the firewall. Problem gone

 

Thanks for the info.I will look at the heater hoses and zip em up.I will check the heat shields also.At least now I know where to look.Thanks...