I own a 2006 cadillac srx awd, with a v6. It is making a strange rattling sound at accelleration and decelleration. It has gone from this to doing it 90% of the time. Any ideas. I took it to a cadillac mechanic to look at and he said to change the oil to non-synthetic to see if this helps. Other than that he did not find anything he could fix or diagnose.

 

I recently bought a used 2006 srx with the v6 awd. It ran awesome for the first 4000 miles but has recently started making a strange rattling or gear grinding sound when I accelerate or when decellerating. My mechanic said he couldn't find anything wrong. He did witness the sound and siad to change the oil to non-synthetic once and see what happens. Any input would be greatly appreciated. My mechanic is from a leading cadillac dealersip in town with a very good reputation, so I kinda trust him, would just love some input.