kenworth w900l suddenly really noisy

I'd start with checking the exhaust system for holes or leaks. Black soot on the exhaust and nearby components will indicate a leak. Could also have a broken muffler.

 

Sounds to me like a flex pipe came loose or broke. Is the noise coming from the stacks or under the cab.

That drastic of a change I would have already been under the truck and I am no mechanic. A break in the exhaust is an out of service.

 

^^^^

Exhaust manifold gasket ?

Yes you need to check exhaust system with a flashlight and look for leaks. You'll see black soot anywhere there's a leak....

 

A break in the exhaust system is not out of service, although it is a violation. According to the CVSA out of service handbook, the only time exhaust is out of service is when there is a leak forward or underneath cab or sleeping compartment, for vehicles other than diesel powered and when the placement of exhaust is touching combustibles.

 

And where exactly do you think the flex pipe is located?

 

It will be under the cab on the drivers side.

 

I'm thinking, that with a Jake brake it's a diesel, so the "other than diesel" that I quoted doesn't apply. Seeing as I was inspected and not put out of service for a hole in the elbow to the stack, that it only applies to engines other than diesel.

 

More then likely when you had your trans and clutch done they had all your exuast off under the truck . Probley just a clamp forgot to tighten up . I'd get under there with it on high idle and feel around I'm sure it wouldn't be to hard to find