I have a 2012 Denali 2500HD that I have to get back to being emissions compliant, I live in AZ. I've already installed all the egr valves and coolers, so now working on the cat and DPF, spent a couple of hours today trying to get the cat in but not having any luck, I jacked up the transmission and removed the crossmember but still no luck, just wondering if anyone has the install procedure for this??
LML catalytic converter installation procedure
- Thread starter r_olsen
- Start date
Should go with the trans cross member out and the heat shield/exhaust hanger removed from the trans. Keep wrestling it 
Yes u need to jack up the trans as far as you can and you can also heave it towards the driver's side a pinch
I believe that it would never fit from the back unless there was no axle at all.
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That's what I'm saying. The cat is the short piece with the injector in it. Why would taking out the rear shock help? Lol
Yep.
Op, to reinstall the front pipe with the regular cat, you will need to do what I said in post # 7. Then, if installing the dpf/doc still attached to the tailpipe, you have to bring it in from the passenger side in front of the axle. Snake it up and over the axle. That part is pretty difficult. One of those jobs where you have to hold your mouth just right and it goes in. Will help to jack up on the hitch if the truck is on the ground. Or if on a lift, it's already at full extension
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Op, to reinstall the front pipe with the regular cat, you will need to do what I said in post # 7. Then, if installing the dpf/doc still attached to the tailpipe, you have to bring it in from the passenger side in front of the axle. Snake it up and over the axle. That part is pretty difficult. One of those jobs where you have to hold your mouth just right and it goes in. Will help to jack up on the hitch if the truck is on the ground. Or if on a lift, it's already at full extension
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Thanks for all the help, but no luck today, spent a couple of hours scratching my head and wrestling with this thing, I can get in but only with the bend at the front, where it attaches to the downpipe, either facing down or to the side but cannot get it to rotate around so its facing up. The hangup appears to be at the crossmember that is just behind the transmission crossmember, which I removed, does one side of this other crossmember need to be let down?
It works, I think we dropped another small bracket and took my entire exhaust out in one piece...
I'm saying do it that was because I did it, it definitely works and is definitely hands down the easiest way, the whole shebang
There is no way. You will never fit the elbow that connects to downpipe past the torsion bar mount. Even at that the cat won't fit also.
Your right. I just went back and looked at my old pictures. We took the dpf and tail pipe out in 1 piece and doc separately. I remember jacking up the trans now.
Thanks for everyones input, I got the cat installed today, it does just take a lot wiggling it just right, I did jack the truck up at a slight angle from just under the passenger side rear door that seem to help, but like others have said you just need to wrestle it in.