Weird ticking noise, not type writer tick.
 

I have yet to find any other problems like this one, I have asked on the Duramax forum and I haven't got a good answer yet. I'm hearing a weird tick while the truck is under load, it started out between 2000 and 2500 rpm and the tick would match rpm kinda like an exhaust leak on one cylinder. It seams to be getting worse because it now does it under less load and it even will tick or pop once at start up. I originally thought it might be the fan hitting something because how much the engine twists thus I wasted 2 hrs and $150 on a drivers side motor mount thinking I had broke one and all diag of the motor mount it looked to be broken, but I have since moved away from that theory. I pulled the wheel liners today and checked the exhaust manifolds to see if I had an exhaust leak and nothing looks out of the ordinary and I would think an exhaust leak would be more consistent . As I said above it will make the noise once at start up and it sounds like a high pressure spurt of air almost like compression leak but I don't know where that would be coming from. The truck runs fine and like I said in the title its not the type writer tick I know what that is. I'm stumped at this point and I feel like its gonna have to break so I can figure out what it is and hope it isn't something expensive.

2009 LMM 250,000 miles, straight pipe, hp tuners tune with DPF delete pulled from old efi live tune.

Mine started off with a tick like you mentioned above and progressed the same, it was the copper washer between injector and head. Look for soot around the injector holes. I have a lly but its an idea.

Will do, thanks for the reply.

Dead on, nice call. I didn't see a lot of soot around it, but I had a buddy on mine help check it and we could both feel it blowing past the injector on the number 2 cylinder. At least this one will be easy to pull and replace the o-rings and copper gasket.

Thanks for the help.

Glad it worked out for you. Install tip, pull the fender liner out and take the tire off, it makes for much easier access then trying to bend over the top of the fender and reach down.