possible turbo going out?
 

My parents have a 2002 GMC 3500 with the duramax. At highway speeds theres a rather high pitched whine that changes with how much your pressing on the throttle. It doesn't seem to make any boost till it hits about 2000rpm either but I can't confirm that as there isn't a boost gauge yet. The oil pressure seems unusually high as well around 70-75psi when cold. It does have 249k miles on it.

Re: possible turbo going out?
 

Any power loss? Check your charge air cooler pipes for a leak. Also are there any trouble codes? Nothing abnormal about the oil pressure.

Re: possible turbo going out?
 

I had a similar issue on a a work truck some years back, the whine/whiles i was experiencing was from a rip/hole in one of the rubber elbows on the turbo pipes. check that. never know right?

Re: possible turbo going out?
 

Also, check for an exhaust leak before the turbo. Exhaust leaks sound a whole lot different when they are before the turbo.

Re: possible turbo going out?
 

I'll take a look at the turbo piping when I get a chance.

How would you check for an exhaust leak on the turbo?

Re: possible turbo going out?
 

Physically look at the manifolds and up pipes.

Re: possible turbo going out?
 

You will see trails of soot anywhere you have exhaust leaks on the manifolds or up pipes. You may have to pressurize the intake side to check for boost leaks. Use a regulator and start around 5psi or so and go up. If it's relatively stock, going to 20psi is probably sufficient.