I have a 2003, see signature, and am now wanting to change the exhaust and let it breathe a bit better. I have searched and read a bunch of threads on changing mufflers, doing turbo-back systems and so on. I need help with the terminology more than anything I think. I know the system from the turbo is 3.5" to the muffler, then 4" from muffler back. I have my pyro probe installed post turbo in the cast elbow.

Is the stock cast elbow on my 2003 3.5" or 4"?

What is needed to go 4" all the way back? Do I need to change the cast elbow right after the turbo? Would a 4" downpipe from a 04 or newer model fit on my existing elbow?

I want to go to a straight thru muffler design, and I know the input of the muffler is offset from the output. I've heard talk of a "S" pipe, is this to eliminate the offset?

I know I've asked a lot of questions, any advice is always welcome. I'm hoping this is something I can do in the driveway. From everything I've read it sounds like it should be.

Thanks

 

Your stock elbow is probably 3.5" although they were some instances where people found they had a 4" unit. I removed my stock elbow and bought a Banks 4" downpipe and made my own exhaust with a Magnaflow muffler. I was able to cut the small amount of 3.5" pipe off the stock tailpipe and fit the muffler right onto it. YES, the inlet of the tailpipe is 3.5" and flares out to 4" and your muffler is 3.5" on both ends.
You could probably find a cast elbow off an 05 or newer truck and run it. They are 4" on both ends.

 

Today I went to my local dodge dealer and spent 1/2 hour getting the part numbers and prices. Most of the time was spent educating the parts guy on what a exhaust elbow and down pipe was . Anyway for a 03/04 you need a 04.5 and up exhaust elbow and down pipe with two clamps. Then go to a freightliner truck parts dealer or equal and ask for a nelson 51",4"/in/out muffler. The straight thru nelson is not offset (like stock) so now you need to deal with matching the downpipe to the muffler inlet and buy two clamps for the muffler. After pricing the whole hassle I think it is better to get the turbo back 4" stainless system (many choices). Then again I'm thinking of trying to find some used 4" elbows and downpipes that guys have changed out to stainless at the local diesel performance shops? Maybe I good save big dollars and save getting into trouble with the wife