So, my old F150 had a 36 gallon tank from the factory, I was really surprised that the Ram 3500 only had a 32 gallon tank. In recent experience of towing with this truck, 9-11 mpg is what it seems I should expect.

That gives me a range of about 200 miles before I want to fill up – I generally won’t tow past 1/2 a tank and get nervous at 1/4 tank remaining. Last thing I want to do is get stuck in the middle of no-where looking for diesel.

Currently, our trailer is a bumper-dragger, but who knows, in the future we may have a 5th wheel – and this truck came with the “puck” system in the bed for a 5th wheel or gooseneck system.

There’s a few tanks out there designed for these types of trucks. I wanted an aluminum tank as I’ve read too many horror stories about rust in the tanks causing problems with the fuel systems of the trucks (or just simply clogging the expensive fuel filters).

After reading for weeks on end about the pro’s and con’s of all the manufacturers out there, I settled on the RDS 72773 tank/toolbox combination. While it’s not quite a full size chest toolbox for the truck, it’s enough to store some tools, straps and other miscellaneous things that I don’t wanna store in the interior of my truck.

RDS makes a TON of tanks with great reviews. They even make a special “diesel install kit” for each variation of Heavy Duty/Super Duty truck to make sure that everything works as intended. Note: these are gravity fed tanks, they are perfectly legal (within the USA) for DIESEL ONLY. DO NOT attempt to use a gravity fed tank with a gasoline powered vehicle. In my research, the best option for gasoline powered trucks is a product by Transfer Flow; they are DOT legal.

Once my tank and install kit arrived, I was impressed with how well built the RDS kits are. This tank is built to hold 45 gallons, however you only get to use 95% of it’s capacity – I was anticipating this and figured I’d fill it up to 40-42 gallons, which is exactly what I was looking for. I don’t plan on driving 700 miles a day when towing, however it’s nice to not have to worry about filling up with the trailer attached. We’ll be able to drive wherever we are attempting to go, un-hitch and fill up both tanks comfortably.

To install, you will need to drill 3 holes in the truck bed. 2 bolts hold the tank down, and a 3/4″ hole for the fuel hose. I ended up cutting a section of old air-tool hose and wrapping that around the fuel hose as it went through the hole in the truck bed, to protect the fuel hose from abrasion and subsequent leaks.

I had a buddy help with welding the fuel neck; I have no illusions that I’m a master welder after my short stint into the welding world. He’s been doing it along time and I’m constantly amazed at the work he does.

Note: the RDS install kit does NOT require welding. I decided to go this route versus using the included splice pipe because, well, I thought this was a better solution for what I wanted. I have ZERO doubts that the kit they build (and include) would have been more than sufficient. I just wanted to do things my way.

After everything was done, I added 40 gallons of diesel to the tank, stopping in 10 gallon increments. I did this so that I could mark the gauge on the tank at 0, 10, 20, 30 and 40 gallon gradients. I figure in the future, it would be nice to have an idea of exactly how much fuel is in the tank – I wasn’t sure how accurate the fuel gauge would be. Turns out 0, 20 and 40 were spot-on. 10 and 30 were a hair off. However, now I know exactly where it is!

I’m really happy with this tank/toolbox combination. Frankly, I probably would have been happy with tanks from any of the big manufacturers (RDS, ATA, KSH, TransferFlow), but this was the best size and had the best price point for what I wanted in a tank.

For those that are wondering, this tank will work with a lot of the 5th wheel systems that interface to the Ram 3500 5th wheel prep “puck” system. My truck is a ’14 Ram 3500 MegaCab. Larger, non-tapered tanks would block access to the pucks.