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Unread 03-23-2009, 05:25 PM   #1
lupinsea
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Stock Gas Tank Modification: Free Ground Clearance*

* Requires 1" body lift



.

Jeep Gas Skid Modification



CONTENTS

1) Vehicle Setup
2) Peformance Review
3) Modification Write-up



1) VEHICLE SETUP

A 1" body lift needs to be install prior to this modification



2) PERFORMANCE REVIEW

The stock HD skid plates found on some TJ Jeeps provide sufficient strength for general trail riding with the thicker steel, full coverage on 5 sides, and reinforcing ribbing. But it hangs down a fair amount (Fig 1). By utilizing the gap created between the chassis and body created with the installation of a 1" body lift, the stock gas tank and skid can be tucked up for increased ground clearance for essentially free. This improves the departure angle and reduces the number of times the tail end scrapes coming off a ledge or over a rock.


Fig 1. Stock gas tank skid plate hangs a bit low vs. after the mod




3) MODIFICATION WRITE-UP

Preparation:

The fist step is to make sure there is very little fuel in the fuel tank. At 6 lb. per gallon the gas adds up quick and it's a dynamic load that shifts around as you try and get the fuel tank out. So it is best to do this right before you have to refuel your Jeep.

Next, depressurize the fuel system by removing the fuel pump relay (Fig 2) and crank over the engine for a few seconds. Replace the relay and disconnect the ground from the battery for safety. Jack up the rear end and set on jack stand, remove driver's side tire for better access to tank connections (Fig 3 and 6).



Fig 2. Removing the fuel pump relay from the PDC for fuel system depresurization



Fig 3. Set rear axle on jacks stand, remove driver's side tire for better access to tank


Disconnecting Fuel Tank:
Remove 8 screws securing filler cap bezel to body and filler tube. Replace gas cap to keep dirt out of filler tube (Fig 4). Reach into fender cavity and snip zip tie holding axle breather tube to filler tube (Fig 5).



Fig 4. Remove 8 screws holding fuel bezel to body and tank filler tube.



Fig 5. Cut zip tie holding vent hose to fuel filler tubes.


Disconnect wiring harness, fuel line, and evap line from gas tank (Fig 6). Wiring harness plug - slide red clip down, then squeeze button on chassis-side of the connector and unplug. Fuel line - squeeze ears together and gently work fuel line connector apart. Evap line - simply twist off the rubber hose.



Fig 6. Make necessary disconnections to fuel, wiring harness, and evap lines.


Tank Removal:
Support gas tank/skid with a floor jack. Remove the 7 skid plate nuts (3 front, 4 rear). Gently and slowly lower gas tank/skid. It may help to tilt tank to the passenger side to slip out the fuel filler tubes on the driver's side. Unbolt the straps and lift the plastic fuel tank from steel skid plate. Clean out any dirt that accumulated in the skid.



[ continued ]

.

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Unread 03-23-2009, 05:25 PM   #2
lupinsea
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.


Modifying Skid Plate:
Cut mounting flanges off steel skid plate (Fig 7). Allow for sufficient overlap of metal when planning the cuts, typically, right at the main tank level is good but preserve the strap mount slots on the front.



Fig 7. Cut the three mounting flanges from the main skid plate body.


Grind off paint from area to be welded. Over lap the mounting flanges 1" lower on the skid plate and clamp into place (Fig 8). Stich weld back together (Fig 9). Alternatively, you can clamp, drill, and bolt these pieces together. Bend the front of the skid plate between the mounting flanges inward slightly for a hair more track bar clearance (Fig 10).

If the straps need to be lengthened, cut and weld in a piece of thin steel or elongate the front strap slots. Clean up all welds and hit with some spray paint.



Fig 8. Re-align flanges 1" lower and clamp into place.



Fig 9. Stitch weld (or bolt) the flanges back onto the skid plate body.



Fig 10. Trim excess steel and bend for greater track bar clearance.


Reinstall Skid Plate:
Reinstall gas tank and modified skid plate in the reverse order of removal. Having an assistant helps a great deal. For those with a rotated pinion the clearance to the track bar will be tight but can be improved with the techniques here. The rear shock is also tight for shocks with a rigid dust shield.




Welding Alternatives:
There are two alternatives to welding the skid flanges back on:

1. Do a bolted connection with the overlapping pieces. Clamp the pieces with a 1" overlap and then drill the bolt holes.

or

2. Trim off the stock flanges closer to the factory bends and then re-bend your own, new flanges with the remaining steel. Drill new bolt holes in the same locations on the new flanges.



.
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Unread 03-23-2009, 05:31 PM   #3
tufrthnails
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Sweet Write-up man. I will have to look into this. I don't know how many times I have dropped into a deep hole and been sitting on the tank skid.
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Unread 03-23-2009, 05:37 PM   #4
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Nice write up! One question though? If you have to buy a 1" body lift (unless you already support this in your Jeep) how is the 1" clearance free? lol, just giving you a hard time.Nice illustrations!
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Unread 03-23-2009, 06:36 PM   #5
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One thing I saw on a 4x4 show was, if you pull the tank for any reason - flip over the straps and bend them the other way. There is a folded "lip" which can rub a hole through the tank over time. By putting the exposed edge "up" - its away from the tank.
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Unread 03-23-2009, 08:15 PM   #6
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Thank you, best writeup I've seen.
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Unread 03-23-2009, 08:50 PM   #7
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Quote:
Originally Posted by tjthorson View Post
One thing I saw on a 4x4 show was, if you pull the tank for any reason - flip over the straps and bend them the other way. There is a folded "lip" which can rub a hole through the tank over time. By putting the exposed edge "up" - its away from the tank.
you sure you did not see that from Jeff@rokmen in their install video?
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Unread 03-23-2009, 09:55 PM   #8
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i cant believe ive never heard of this, great right up!
so i found a new use of a 3in BL gains 3inces of gas tank clearance, im gunna order another 3in bl tonight











joking of course
great write up
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Unread 03-24-2009, 12:35 AM   #9
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Excellent write up, I love seeing stuff like this the average person can do without spending $$$.
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Unread 03-24-2009, 01:47 AM   #10
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Quote:
Originally Posted by TJSport01 View Post
i cant believe ive never heard of this, great right up!
so i found a new use of a 3in BL gains 3inces of gas tank clearance, im gunna order another 3in bl tonight


joking of course
great write up

lol, there's a crossmember in the way of much more than a inch.. I put a thread on jp about 2years ago on raising the stock tank skid.
you could put it in there at an angle tho... lol. check out the may09 issue to make it stronger.

nice job OP...
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Unread 03-24-2009, 09:52 AM   #11
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Quote:
Originally Posted by Tumelin View Post
Excellent write up, I love seeing stuff like this the average person can do without spending $$$.
While I agree this a good mod for many, the "average" person doesn't have access to a welder and doesn't know how to use one.

And yes, this was an excellent write up. Thank you, Jay.
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Unread 03-24-2009, 10:01 AM   #12
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The average person however probably knows someone who does own a welder and knows how to use it!
Great write up, I will be doing this soon as my filter on my fuel pump is clogging up anyways
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Unread 03-24-2009, 11:32 AM   #13
lupinsea
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Thanks everyone.

A few points for clarity:

Credit and Thanks
I was first tipped off to this by Mr.Blaine in one of his many posts. Did some searching and found a few other stock gas tanks skid modification write-ups out there. Thanks to Mr.Blaine for tipping me off and for the other pioneers and their write-ups. I tried to take a lot of photos and fill in where some of the other posts were a bit weaker or didn't include some info.

Limit on Raising
There is a limit to how far you can lift the gas tank before you hit the cross member the shocks are mounted to. There's also the issue of the driver's side shock clearance to watch. I figure 1" is a good, safe amount of raising. Beyond that I "think" you could make it work but it might take a lot more effort (relocate shock mounts, etc.). A simple cut and weld of the stock skid seemed straight forward.

Alternative Methods
There are also two alternatives to the cut-and-weld approach. Both pretty much follow the above write-up. One involves cutting and overlapping the flanges, then bolting them back together (instead of welding).

The second method has the flanges cut off RIGHT at the bend. Then the author marked a line 1" below the cut and bent the verticle mounting "leg" 90 deg to form a new mounting flange. The folding usually involved clamping some 1"x1"x36" long angle iron to the skid and hammering the bend in. Bolt holes were then transfered and drilled.

Neither of these alternatives requires a welder and both can be performed with either an angle grinder / sawzall / jig saw and a power drill.

Flipping the Straps
When I took the straps off I didn't see any areas where they were rubbing. The straps are actually securred pretty tight so there's not much movement. Besides, I didnt' see any folds or lips along the straps where it would rub. Besides, part 2 - there are these plastic triangular ramp-like-things riveted to the top of the straps, my guess as a factory spacer or something. So you can't simply flip the straps over.

"Free"
Ha, ok GOLENJEEPTJ, you have me on that point, sort of. "If" you already have a 1" body lift installed, then you can get an extra 1" of clearance free. I think for most of us the 1" body lift is installed for other reasons (tire clearance, belly-up skid clearance, etc.). So it is usually already "there".
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Unread 03-24-2009, 11:54 AM   #14
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I've always wanted to try to cut that cross member off and move it up to gain more clearance for the gas tank.

On a body lifted TJ, you could just remove the body lift pucks there and move the cross member up however tall the body lift is.

Added this to the FAQ, nice write-up Jay.
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Unread 03-24-2009, 01:04 PM   #15
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Quote:
Originally Posted by Border Dave View Post
While I agree this a good mod for many, the "average" person doesn't have access to a welder and doesn't know how to use one.

And yes, this was an excellent write up. Thank you, Jay.

The writeup clearly gives an option to welding. Imo, the average person would absolutely have access to a drill and beable to use the alternate method. If they aren't comfortable doing that then they have no business trying to raise their gas tank by modifying the skid.

"Grind off paint from area to be welded. Over lap the mounting flanges 1" lower on the skid plate and clam into place (Fig 11). Stich weld back together (Fig 12). Alternatively, you can clamp, drill, and bolt these pieces together. Bend the front of the skid plate between the mounting flanges inward slightly for a hair more track bar clearance (Fig 13)."
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