Ram 2500 Diesel

Please go to this website and check the specs for your particulate vehicle.
https://www.ramtrucks.com/towing-guide.html
You won’t be lacking power as the 6.7 can handle your trailer.
It’s nice everyone is offering advice, suggestions, and opinions, but why not ask the people that designed and built the truck.
Go to the website.

stapler101 wrote:
I have a 2018 Ram 2500, diesel, short bed, "standard" rear end.
I am considering a 42 ft 5th wheel trailer with an empty weight of 12K.
Will my truck handle it on cross country trips with hills and mountains?

As long as you are not concerned about being over the manufactures 10K GVWR. Hopefully you have a trim level with 18" or 20" rims and tires. Tradesmen without chrome package have 17" rims and tires as a standard.

Then to comply with Texas registration you will have to pay the higher fee for vehicles 10,001-18,000.

We towed a 16K 39'4" 5th wheel with a combined weight of 24,500 pounds. We were loaded heavy for full timing. Our 5th wheel had a 2435 dry pin weight, yours is 400+/- lighter, so you should be able to stay under the manufacturers 6500 RGAWR. Our truck was 8900 pounds ready to tow. Factory pucks, Demco 6099 picture frame and B&W manual slider. I would not worry about air bags until you test the load on the truck ready to travel. I towed at 60-62 MPH in 5th gear, my truck with not shift to 6th in tow haul until over 65 MPH, however I locked out 6th anyway, mainly for down hill reasons.

If the trailer is loaded heavy and extend trip weight in the truck you will be around 11K on the truck. I was 11,740 pounds on our 2015 3500 4X4 CC SB Laramie with Aisin tranny. Again the truck was loaded pretty heavy for full timing with tools, EU2000i, gas, two sets of golf clubs, on and on.

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Texas registration:
ALL VEHICLES
6,001 lbs. – 10,000 lbs. = $54.00
The annual registration fee for a vehicle with a gross vehicle weight of 6,001 lbs. – 10,000 lbs. is $54.00, plus applicable fees and local county
fees.
Note: The gross vehicle weight of a truck is determined by adding the empty weight of the vehicle and the heaviest load that will be carried by
the vehicle (carrying capacity) during the registration year.
WEIGHT BASED REGISTRATION FEES
Vehicles 10,001 lbs. or more will pay the following registration fee*, plus applicable and local county fees
10,001-18,000 lbs. $110.00

BTW I was licensed to 12K in the State of Washington.

wanderingaimlessly wrote:
Yeah , it's sad, but the coil suspension makes that light riding truck, have very little payload after you allow for the diesels weight.

Sorry my friend, but that is 100% BS.

The 2380# payload is typical for the 2500 crew cab diesel class and has zero to do with the rear springs, and everything to do with the 10k weight limit for class 2 trucks (that is until GM changed the rules sort of, but that's another topic).

All that means is your truck weighs 10,000 - 2380 = 7620# empty as it sits.

The coil spring rear suspension gives a better ride, empty or loaded, but does not reduce the available payload. Trains engines ride on coil springs, and I think they're pretty heavy.

Yeah , it's sad, but the coil suspension makes that light riding truck, have very little payload after you allow for the diesels weight.

the trailer I am looking at is a Wildcat 384mb with a hitch weight of 2080 and dry weight of 12443,
I did not know about the door sticker until your post.
My door stickers shows 2380.

I looked at that same truck hard for a smaller 5th wheel and decided no.
A handful of the 2500's have good capability but most of the Rams are very low on payload capacity, and a 12000 empty will be a 13500 at best loaded unit meaning your pin weight will be north of 3200 lbs, add for the hitch another 200, and then any others travelling with you and most Rams are overloaded.
Tow cap will show as ok,
Payload will probably not.
Some may say different, and to actually pull it you will have plenty of power, but your suspension and frame will be technically overloaded in most cases. Check your door pillar sticker and you should be able to find your numbers, your old window sticker if you saved it should tell you as well.