Quite a few years ago I had a leak in the underseat gas tank, which soaked the carpet and seat belts and just generally made a terrible mess.  A rear-mounted gas tank is a nice upgrade.

The solution was to install the rear-mounted gas tank from a ‘78 and up CJ in the rear of my early CJ5 (now repeating the install on my CJ6).  I purchased the tank, skidplate and fuel sending unit from 4WD Hardware.

The new tank is 5 gallons bigger, the Jeep rides better, and in place of the old tank I can now carry a decent selection of tools, spare parts and supplies, a tow strap, and my lug wrench. While not as big of an issue with the CJ6, in a CJ5 this added space is invaluable.

The only downsides were :

- having to hack off a pretty new exhaust, since it ran right through where the tank needs to mount:

- and having to cut out the bracing for the original drawbar rear bumper:

I had this tank installed in my ‘66 CJ5, but found that with the body mounts all fresh on the CJ6 it changes the installation a bit.  Before I had to use some straps at the front of the skidplate to attach it to the frame.  Now, all I had to to was bend the top front portion of the skidplate back a bit and I can bolt it directly to the frame.

At the rear, the skidplate uses four bolts that go through the rear crossmember, but with the tank in there the middle two bolts are impossible to get to for tightening. The solution was to weld nuts on the top side of the rear crossmember for the skidplate bolts to thread into:

We now have the space, but all the underbody and inside frame rails need to get painted before the tank goes in.  I used Hammerite.  Before:

After:

Here’s the gas tank and skidplate after being painted with the hard to find Hammerite.  A bit shiny for my taste but I’m not going to fuss with it—maybe they will clean up easier.

Here’s the tank all prepped for install.  Note that the skid plate cradles the tank, and the tank is strapped down to the skidplate:

For fill hoses I went to a place that supplies pnuematic and hydralic parts, and ordered rubber hose that’s rated to carry gas.  It’s not the cheapest stuff in the world, but it won’t swell up like normal radiator hose.

Tip - remove the nuts from your shackle bolts, and hammer the bolts flat with the shackles...this will subtract one place where the tank will get hung up trying to install it.

Here’s the tank installed:

For a fill, I used a CJ7 setup and mounted it in the passenger side rear corner.  It just looked more natural there, and made the hose routing much easier as it’s a pretty straight shot down and into the tank:

Here’s a look at the exhaust routing to accommodate the rear tank.

A note on fuel gauges - I was never able to get the late gas tank to speak to the early gauge, but then again I could never get the original tank to speak to the early gauge.  It might have been a faulty gauge, I can’t say for sure.  At the time I had an electric fuel pump that would start to chatter when the fuel level was low - it functioned as an audible gauge…

The current setup - with SSDutch’s intermediate-era Speedo cluster - works fine.  It’s really strange to have a working gas gauge after 19 years of doing without.