As far as cutting the tab off the bellhousing, thats typical with headers on the 4l80....most 2500s with the 4l80 the exhaust runs under the front of the trans and the pipes run over to the passenger side and have hangers that slide into the mount onthe passenger side of the trans.. Then both cats are behind the crossmember, then the pipes go under the rear crossmember

 

Hmmm. I have not tried running the pipes under the rear cross member yet. Over seemed to fit pretty decent but ground clearance is not an issue so I will see how that lays out as well. As far as mounting it to the side of the trans, I was kinda headed that way with making something work out of the heat shield I removed.

 

Header wrap would probably be a good idea as would a heat shield on the passenger side of the transmission.... Look for one from an 09 express van.... Its just a shied the exhaust bracket is on the extension housing bolts....

 

I will check that out. I am gonna take the saw to the factory hanger/heat shield tomorrow and see how it sits in there now that I was able to space the pipes out quite a bit where as before the factory heat shield wasn't even an option. Also, thanks alot for the suggestions man, I really appreciate it.

 

Are you done already... I want to know how it sounds and if there is much drone... I'm ready to buy full exhaust for my 25hd crew LB .. 3" lift also. Where did you end up with tail pipes.....

 

Nope, not done yet. I am hoping to button it all up tonight or tomorrow afternoon. I hung the muffler on the factory muffler hangers, so it is dumped about a foot or more in front of the rear axle.

 

Thank you for install pics on the 4L80E. We weren't sure if it would work on that trany or not.

Sean

 

I Got it all in and clamped up this evening. I am super happy with how it turned out! I have a few tweaks to make where it is touching the cross members, but overall getting it to fit was not bad with using a bit of extra pipe and mild persuasion from a few hand tools.

 

Cool.. Was the 2" extension at the driver side collector the only extra pipe you used. How is the cab drone. I'm running air bags and don't need the added heat ... May have to go full dual to the rear. Have to cut cats in here to so that adds at least 12" more. Which pipe is touching cross member?

 

Sean, did you have any of these issues on your in your installs.