I have been planning to do the full 4" exhaust upgrade...that is until I got my pacbrake working properly, now i wanna keep it. Right now I have just straight 3".

I can get a 4" adaptor and place right under the cowl area, and run my 4" back. Will it help anything, or sound better than the straight 3"?

Just dont wanna waste the time for no benefit.

Thanks

 

Is the pacbrake mounted to the turbo? If so than yes running 4in from there back will help with egt's if you start pushing more fuel. The stock 3in is crushed pretty good where it goes around the t-case and over the axle. It will start being quite restrictive.

 

The pac brake has a cast 45 deg adaptor bolted to the exhaust housing, and it turns down in front of the cowl, so more than likely, ill let the 3"exhaust pipe keep going, and then once it turns to head towards the rear, ill weld in my 4", run it back and out in front of the axle. Im running 3" now out under the bed, but i would like a deeper sound rather than makining an attempt to blow the rear window out(exhaust exits right below the back window)

 

When I started my 4in, its still not finished, I have my 4in starting at the end of the downpipe, right when it turns towards the rear, and I just made it turn down before the rear tire. It sounded awsome!!! However around town it was fine empty on the highway wasn't too bad but when I hooked up to the trailer towing down the highway was a terrible drone it was bad with the windows up but with them down aaaahhhhh!!! Needless to say the next week I finished it and put it out back over the axle with a turn down. Now I don't have any drone but still sounds nice outside.

It did sound baddass with it dumping out in front of the rear tire though!!! Sounded like a big bad semi!!

 

It will have a deeper sound. It does sound better than the 3 inch straight to me.

 

I got some good benefits when I changed to a 4 inch system (3 inch downpipe, then 4 inch).
I gained 3 psi boost, got noticably quicker spoolup, and much faster cooldown. Plus the sound is great, even with the muffler in there.
Go for it.
Jay

 

has anyone worked with 4" flex pipe like the big trucks use? like to go over the rear end?

 

May I suggest that you save yourself time and money get the parts from diesel performance. I did and had it running in four to five hours. It comes with or without a muffler and exhausts behind the rear wheels. I even added a 5 inch stainless tip and hangers all for about $300.00. The kit starts behind the bottom elbow of the down pipe and clears the frame, my transfercase and tranny. It pretty much follows the stock location but lower. In fact the kit went in without jacking up the truck which is a big plus in my book.

 

Yep I did. Super easy to install, especially around the t-case. Only problem is I used the cheap stuff instead of the expensive stainless steel kind. It rusted out after 2 winters. Unforunatly the stainless steel stuff is about 2/3 the price of a pre-made kit so its not really worth the effort.