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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.

Note - the detail on this page is all I have. I don’t have part numbers, measurements, or knowledge of the current gas tank offerings for additional options. Please contact your Jeep parts supplier for additional input. 

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:

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.

Comments are closed, but you can read the comments other people left.

1. Gilles on July 03, 2004

   Hi!
   My underseat tank is rudted and i have an old but good cj-7 tank in my garage. I want to put the tank rear like you did. But i don’t like the fact that i have to cut out that brace. My fear is that the general stability of the frame gets worse in off-road. What do you think?

2. Michael Boyink (Author) on July 04, 2004

   Hi Giles -

   I think that bracing served to strengthen the rear of the Jeep - for using the drawbar bumper and 3-point hitch setup.

   Newer Jeeps with the rear gas tank didn’t have that bracing, so I think you’re fine.

3. Clarence on July 26, 2004

   Hi, I just bought a ‘67 CJ5 and I want to do this mod to it ASAP. Mainly for interior room and aftermartket seat install. My question is: Do you have any pics of the re-routed exhaust? If so, could you please post them or email a few to me?
   Thanks, Clarence

4. Michael Boyink (Author) on July 26, 2004

   http://www.boyink.com/supersizedutch_comments/12_0_9_0_C/

5. Michael Boyink (Author) on July 28, 2004

   Just remembered I also have this pic of the exhaust after removing it:

   http://www.boyink.com/Jeep/Images/IMG_3945.jpg

6. Jim cj-6 owner on July 29, 2005

   Hi guys did this rear tank addition years ago. Got lucky looking around my dads yard.(He owns a trucking company)I had to remove the cross bracing and make up my own brackets,with a little bit of grinding on the inside of the frame it went in pretty nice. I kept the old tank under the seat and used a cross over switch from a 80’s ford p/u. Everything works great. Only I don’t have a skid plate but that hasen’t been a problem yet

7. Greg Smith (gscj5) on September 30, 2005

   Hey Mike you said something about using straps on the skidplate to hold it to the frame…was that the CJ5? If so will that be a modification that needs to be done for a CJ5?

8. Michael Boyink (Author) on September 30, 2005

   I used the straps on the CJ5, but not because a CJ5 is different from a CJ6 in this spot - the back ends of the Jeeps are identical.

   I had to use the straps on the CJ5 because the body was sagging so bad, the tank didn’t fit up into the frame rails as far as it should - the tank top would hit the body bottom, which didn’t let the front of the skidplate reach the frame crossmember.

   If your Jeep body isn’t sagging that much you won’t need the straps.  On the CJ6 I had just replaced all the body mounts, and the body is just plain in better shape, so no straps needed.

9. Greg Smith (gscj5) on September 30, 2005

   One more question…why did you decide to go with 78 and up tank and skid plate instead of 70-77?

10. Michael Boyink (Author) on September 30, 2005

    Can’t remember, exactly…:D

    I think it was to do with the filling hose size (IIRC the earlier ones were much larger), and that I had found a junkyard filler neck and mount for the ‘78 and up.

11. dan on February 13, 2006

    so where did you run your new exhaust after mounting the rear tank.  looking at the dimnesions, the tank takes up most or all of the room under there, where did you tuck the exhaust?

12. dan on February 13, 2006

    yeah, im an idiot, didn’t read the previous Q and A on the exhaust.  sorry and thanks!  looking forward to doing this on my 58 cj6 project

13. Michael Boyink (Author) on February 13, 2006

    Hey Dan - the link in the comments was to the dual exhaust I had on my 5.  That’s one approach.  Up under the last -picture on this page is a link to the single exhaust routing on the 6, which I’m happier with.

14. steve aka zed on June 19, 2006

    sent you an email. but forgot to ask another question. 

    i was looking at the new new rear bumper and what appears to be a horizontal brace.

    can you describe it more? how well does it tow?

    btw, everytime i see a picture of large dutch it looks better and better. nice work!
    thanks

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