1998 gmc3500hd duel fuel tank

[Bradley995]

I got a 1998 gmc 3500 hd it’s a 6.5 diesel I was wondering how the duel fuel tank works does the second tank fill into the first tank once it reaches a certain level

[a5150nut]

Doesn't sound like a factory option. Going to have to start tracking fuel lines. Is there a switch on the dash to go between tanks?

Oh and Welcome to TDP

[joed]

A 1998 3500hd sounds like the pseudo 1.5 ton truck they made for a few years. Weren't those originally cab and chassis? I think cab and chassis trucks had a factory dual tank option and work as you described-one tank automatically fills the other. So no switch.

[a5150nut]

A 1998 3500hd sounds like the pseudo 1.5 ton truck they made for a few years. Weren't those originally cab and chassis? I think cab and chassis trucks had a factory dual tank option and work as you described-one tank automatically fills the other. So no switch.

Wouldn't that have the 19 1/2 in rims if it is?

[DmaxMaverick]

Wouldn't that have the 19 1/2 in rims if it is?

The 3500HD up to around 2002 was a medium duty truck, with a 15,000+ GVW. 19.5" medium duty wheels were standard. They were cab/chassis, and none were fitted with a bed at the factory. The modern 3500HD is a phat 1-ton.

I don't know what year the fuel tank arrangement was changed, but the 1998 should have the aux. tank fill the main tank. Before that, the individual tanks were selected with a switch in the cab that controlled the selector valve.