I am a new owner trying to figure out my full towing capacity on my 8ft bed 2500 with standard cummins engine tradesman
any help would be great as I am planning on a 5th wheel rv
Maximum tow means little. You'll likely never be able to get there with a fifth wheel or any RV without going over payload/axle ratings because all the weight is static. You can't adjust it to get your hitch weight under payload/axle ratings.
I see in your profile you say your trailer has a GVWR of 14,500, and you claim it only has 2088 lb pin weight. Is that the advertised pin weight according to the manufacturer? If so it's likely wrong and based off the dry weight. Fully loaded it's probably closer to 20% of your GVWR on your trailer, or 2900 lbs. With the CTD your payload is likely similar to mine, around 2200, maybe as high as 2500 if you're bare-bones. Even with the lightest hitch and the camper empty you're already close to your payload and that's before you put any gear and people in the truck. You might still be under your axle weight ratings, which is going to be your saving grace, but you're STILL running that truck at close to its max rated capacities. It's not going to be an enjoyable pull.
Will the truck do it? Sure, it will, but it's probably going to squat quite a bit. Mine squats about 2" when I hook up to my FIL's fifth wheel to bring it to their place when he's got too much going on. It's an 11k GVWR (I think it's been a minute since I looked) trailer and has right around a 2k pin weight. My truck does it just fine, but I know I'm over on ratings and drive accordingly. Will your truck blow up? No, the CTD is up to the task, as are your brakes. It's your springs and suspension that are suspect, and it's going to be a squishy ride since you've got coils and a 4-link rear end, not leaf springs.
Personally? With a camper that large, I'd have stuck with a 6.4 gasser if a 2500, or stepped up to a 3500 to get the leaf springs for stability. Don't get me wrong, I love my 2500 but my next truck is going to be a 3500 or an F350 because in a few years we plan on upgrading from our TT to a fifth wheel and I know my wife, she's going to want one with some room for us and the dogs, not a tiny 'couples camper.'