I have a 2010 GL350 with 165k miles. My GL was with clicking sound for about a year when accelerating especially in the morning. The clicking sound has now escalated to sounds of something slipping coming from around the left front wheel if I hit the pedal a little harder. I brounght it to indy a year ago they checked the front wheels, steering column and brakes said nothing wrong. The CEL also came on last month I suspected is the Oxy Sensor which I replaced one of them a few years back. The engine oil keep showing low after about 3 tank of diesel but I don't see any drip in my garage, I have to refill a quart each time. I am using the new mercedes brand 5W-30 listed as 229.52, they discontinued the mobil 1 229.51, maybe it related to my enginine oil problem? My GL had engine seal replaced three times due to leaking, costs $4k from indy each time. Now I use the GL mainly to haul materials for my house remodeling, I don't see it will last for another year... but I really want to keep it longer. Any thought?

 

It's a cost-benefit equation. Are you willing to put the money into the vehicle? It's 9 years old with 165k miles. How long do you want it to last, and how much money are you willing to put into it?

Regarding the clicking - does it change with vehicle speed? Does it ever go away, or is it always audible? Please describe it in more detail.

 

The clicks only occur when I accelerate especially with a little uphill slope. As soon as my GL get up to 20 mph, it runs pretty smooth and no clicks. BTW I took delivery of my GL350 in Oct 2009, so I 've been driving it for about 10 years now. I am a heavy footer so never easy on my GL, that's probably one of the reasons

 

Sounds like the chain inside the transfer case is slipping. The chain can be replaced it’s a straight forward job

 

That's what it sounds like to me as well. You ought to have it properly diagnosed and rectified before it manifests itself into something worse, like a cracked transfer case or "sudden lunging followed by a class action lawsuit...."

 

Thank you guys! I now think it's most likely the chain in my transfer case is slipping. It doesn't look like it's an easy DIY. So far I was able to replace air filters, fuel filters, oil change and all other regular maintenance stuffs but this job seems like another level of difficulty...