25 gallon to 34 gallon gas tank swap, can it be done?

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RichardSwinger

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Hello everyone! So I just picked up a 1998 K2500 Sierra, extended cab, short bed, L29/454 engine. Unfortunately, it came stock with the 25 gallon gas tank. The 454 is thirsty and I'm trying to extend the driving range and add some more weight in the back. I know the easiest thing to do would be to add one of those toolbox style fuel cells in the bed and that would give me like +40 more gallons, but I really don't want to sacrifice the bed space. I know that with the longer 34 gallon tank I won't be able to keep the spare tire mounted under the bed and I'm ok with that. So the real question is... Can this 34 gallon tank swap be done? Has anyone successfully done this? Has anyone added an under bed fuel cell that didn't break the bank? Thank you for your time!

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454cid

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I would thinkthe 34 gallon tank would interferes with the axle in a short box truck. I would assume that's the whole reason why short boxes got the smaller tank to begin with. I would look at the possibility of using one of the rear mounted tanks. SUV's had one, and I beleive some C&C trucks had a rear auxilery tank. You may be able to fabricate mounts where the spare would normally go.
 

Nad_Yvalhosert

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The 34 gallon fuel tank on a pickup is located in the exact same place as the 25. Since you have a 143" wheel base, you should be able to direct swap it in. The fuel filler neck is in the same place, just verifiy the placement of the front tank strap as the front of the tank will extend under the extended cab.
The spare tire is behind the axle, the fuel tank is in front. Only the Suburban uses a rear tank in a 2500 series
 

stutaeng

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Yeah, you need the extended wheel base (long bed) to get that 34 gallon tank.

I know I'm the minority and everyone just loves the short beds, but this is another reason why I like the long beds. This is actually a bonus. The main reason is you can't match an 8' bed for hauling. If you are working the truck, 8' bed is great. Have you seen those dually mega crew cabs with 6.5' or whatever beds on the newer trucks? Body builder skipped leg work, LOL. Man, those beasts are grossly out is scale!

Don't get me started on the CC 1500 5.5' beds. A coworker got one and added added one of those "tough" bed covers. With a toolbox the guy has the size of of a frigging trunk! Had to get a trailer to haul a fridge, lol .
 
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HotWheelsBurban

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Yes I always get entertained by watching the people who buy the ginormous TVs at Wally world and then try to get it in their vehicles. Saw a guy I used to work with put a 65" one in a late model Camaro. Took him some finagling, and he had to ditch the box and fold the back seat down. But he did get it inside. On the other hand, my cousin's 15 ccsb has a toolbox, and when he helped us move a couple years ago, the mattresses had to be really strapped down because they hung half out the back.....and I had a metal shelf unit (one of the lightweight ones that comes flat packed and you assemble them) on top too. We got across Houston, but not super fast. If he really had to haul much stuff, he'd probably get a u haul. The last time we moved, it was 3 trips up South Main and back, Burb fully loaded like I was going to a swap meet.....
 

RichardSwinger

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Ok, so... That's two people says it won't work, one guy says it's mounted in the same spot, and EVERYONE agrees that the in bed aux tank is a bad idea [emoji1787]. The more people I ask about the aux tank the more reasons against it seem to pop up, the only real pro to that aux tank would be the ease of install.

I crawled under there yesterday to do the first post build oil change and there is a surprising amount of stuff shoehorned under there. My dad knows the early flat tappet style big blocks very well and told me about this super duper FOOT LONG oil filter he used in his 427 powered dump truck and still uses in his 454 powered franken truck, but I saw that the front drive shaft is directly under the standard oil filter mount location. There is what looks like a factory installed 90° adapter for the oil filter so the filter sits horizontally vice vertically. BUT that's all on the front end of the truck and the back end seems to have a lot more room to play with underneath...

It's kind of hard to get a good picture of what kind of room there is when I'm laying flat on my back. I'm hoping to get it on a lift once I find a reputable mechanic shop local to me to help me give it a once over. I'm really hoping to find someone who has 1): tried this and been successful, or 2): tried this and knows for a fact that it won't work. Going by the pictures on Summit it does look like there is a difference in the shape of the 25 vs 34 gallon tanks at the front part of the tank, but as far as the length difference goes I think it's barely a foot longer. In studying the pictures it looks like the sherman brand 34 gallon tank is the closest in shape...
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stutaeng

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BTW, your truck is kinda rare as far as I know. ECSB 2500 8 lug. Everything else similar got the long bed in that configuration. I think one member here has one, a white one IIRC.

14 BFF with hydroboost is pretty stout. Is yours 3.73 or 4.10?

Hopefully you can add more fuel capacity.
 
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