Harmonic noise under load
Hi, My first post so i hope I get it right!!
I have a Jeep Grand Cherokee 2006 CRD with approximately 145,000 km travelled. About 60,000 km of that has been towing a caravan. Have noticed lately that there is a humming noise coming and going like a harmonic around 2200 RPM when under load going up a hill and especially when dropping back to 4th gear under load. As soon as the accelerator pressure is eased off the noise goes away. I have done a complete oil change including engine, front diff, transmission, transfer case and rear diff. Appears to be only normal play in the drive shafts and CV joints. Mounts for engine, transmission etc all seem to be ok. Just can't tell from inside where the noise is coming from. Have searched the threads and have found similar issues but doesn't appear to be any definite answers. Any further suggestions will be greatly appreciated.