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Prep for Aftermarket Bumper - Rear Frame Repair

6K views 32 replies 6 participants last post by  MudMagnetYJ 
#1 ·
This thread will follow my project of reinforcing my frame to install an aftermarket bumper.

Over Thanksgiving, I will be dropping the fuel tank and putting on the welding mask. I'd like a bumper to protect my fuel tank, provide better recovery than my current tow hook, carry a bike rack on the trailer hitch, and give my YJ a better overall offroad look.

My rear frame is pretty bad, and the passenger side is rusted to sh!t. The current crossmember is bent, rusted, and warped. It looks like someone carved a pumpkin face into it (picture). Rather than spending $180 on a new crossmember and still not having any frame to work with, I spent $25 on a 4 ft sheet of 3 in flatbar, 3/16 in thick (the sticker is shown in the pics below), and $10 on a 4 ft section of 1 1/2 in angle, 1/8 thick.

YJ frames are notorious for rusting, and are 1/8 in thick. Based on the way it's rusting, it's cheap foreign steel. You can see a welding seam (picture) where somebody successfully patched up the leaf spring mount, but the bottom is completely cut out and is covered by some sort of sheet metal held on by rivets.

I plan on really fixing the frame by lifting the body off, sand blasting the frame, welding it all up, and putting some sort of primer and POR15 or other paint on it, but for now I just want a bumper.
 

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#2 ·
For all intents and purposes, I am a high school senior with intermediate mechanical knowledge.

Here is the plan for Thanksgiving break:
Day 1 - drop fuel tank, evacuate and plug fuel lines.
Day 2 - cut out 12 in section from each side of frame crossmember, sand fuel tank skid plate, weld skid plate, paint skid plate.
Day 3 - weld angle iron to patch bottom of frame, weld bracket into place on crossmember, reinforce bracket by welding in angle iron onto each side, paint.
Day 4 - replace fuel tank and add in tow hooks (until I order the bumper).

Any tips, advice, questions, special photo requests, or anything else are welcome. I will try to document as much as possible of this.

Provided photos are the template I made for the crossmember out of cardboard, the markings on the steel I plan to cut, and a PDF I made of all of my measurements, the PDF I plan to send to the welder who is making my bumper.

I'll cut the steel within the week.
 

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#3 ·
I used the auto-rust repair parts on both sides of my frame in the rear, and for the rear cross member, I used a piece of C-channel that was 1X3X1/4" thick.

I built a rear rock crawler style bumper out of 3/16" plate steel. Now I have bullet proof rear protection. I also added a rear hitch section that bolts on with 6 grade 9 bolts, so I can unbolt it to go wheeling and bolt it back up to tow the trailer.
 
#5 ·
I found the auto-rust section, but it's $170. That's what I plan on using when I patch up the frame really well, if I don't find a brand new frame or decent used frame.
 
#4 ·
Here are image files of the scanned PDFs. The previous post has the PDF file of the annotated template with the measurements.
 

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#6 ·
Here is the Auto Rust section I found. It's part #ART-42R from Morris 4x4.
 
#7 ·
I will keep a spreadsheet of all of the parts I use, and calculate the total cost to me. That way, all of you can get an idea of how much your project might be, and can find all of the parts and materials I use in case you would like them for your own projects.

Here is the template on the crossmember, and how the bumper will bolt onto it. I'm thinking about welding the nuts onto the bracket, at least on the inner portion that isn't accessible by a wrench. I fanangled my hand back in the crossmember to remove the bolts and it wasn't very fun.
 

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#8 ·
All of the holes in my rear bumper and cross member area have blind nuts that are welded into the backside(even the bolts for the skid). Makes things a lot simpler when you want to take it apart.

I used all 3/8" grade9-military bolts and nuts on my bumper build. I get my bolts from www.mcmaster.com. Only place I have ever found for military grade hardware.

The reason that I went with the 1/4" thick C-channel was because the flat plate that you have is mild steel and it will bend and twist, whereas the C-channel has greater strength. That rear cross member is where the rear body mounts hook to. I wanted something that was going to be there for strength.
 
#9 ·
I've seen you posting on a lot of other forums, and your Jeep is a little more heavy duty than mine, so even grade 8 is a little overkill for me. I'll bookmark that site though, I still plan on doing a lot more. In the end, I hope to have a 5.7L Chevy or Cummins diesel, but you know how that is. Engine and transmission upgrade won't do me any good with a bad frame and a Dana 35 rear, so I'll have to have Dana 60s or at least a Ford 8.8 rear.

I'm only taking out a one foot section, and bracing it into the frame, so I don't think the metal will bend. If I was replacing that whole crossmember, I'd use that c-channel steel.
 
#10 ·
Do what you want with the steel plate vs channel vs autorust sleeves but a few things you should definitely do:

- Perform the 20 gallon mod to your gas tank while you have it out. Look it up, it's easy, free, takes about 2 minutes, and adds 5 gallons of fuel capacity to the tank.

- Double check the crossmember in FRONT of the fuel tank skid. Look for rot at the ends where it's welded to the frame rails. Just replaced mine...

- When you put the fuel tank back in, rotate the band clamps on the fuel filler hose and the breather hose so you can get at them with a long screwdriver while everything is mounted. That way, next time you have to drop the tank, you can cut those hoses loose before the tank comes out. Makes life a lot easier the second time.

Good luck.
 
#11 ·
I've looked up that fuel tank mod, but fuel spills out whenever I refuel, and the gauge takes a while to drop after ready full. This made me think that it's already been done, but I still only get about 15 gallons. I understand that you trim the vent hose, but could the long vent hose be the reason that fuel is spilling out? I have managed to fill it up to 20 gallons once before, and that was on a trip to Rush Offroad.
 
#12 ·
Not sure why fuel is spilling.
Seems like it could be due to the breather already being trimmed, and trimmed a little too short.
While you have the tank out, pull the breather hose and see what's up.
If it's been cut, it may be too short, leading to spillage.
If it hasn't, might as well trim it for the extra capacity.
 
#22 ·
The hose has not been trimmed, so I trimmed it to the length of the tube with about half an inch excess on it. I really don't know why fuel spilled out, maybe the breather hose had so much suction on it that it just spit fuel out. It is a very small hose, so it could easily carry the fuel up with a capillary action type thing in the time it took the fuel pump to shut off.

Now that I think of it, the filler neck was just hanging there unattached to the body, but I secured it. Maybe the fuel I was putting in actually went through the breather hose. That almost makes sense because the fuel would then have to reach the fill hose to cause the vapor lock.

I guess I'll find out when I finish up and refuel. I don't really mind as long as I get 20 gallons. Then add the gerry cans on either side and I have 30 gallons. I see a deep woods trip in my future.
 
#13 ·
Would anyone be interested in having a virtual copy of the template? I have access to a 3D printer at school so I may print out a template just as a reference for welding. I can figure out a way to get it up on here and the TJ forum.

My friend and I are also considering making more brackets and selling them, because most people have access to an angle grinder and drill press, but can't get the same precision as we can with the mill. We can make 4 from a $25 piece of flat bar, but there is a lot of labor in this and the full crossmember is $180. There is of course some fabrication involved in my method, but it's cheaper and you gain the experience.

Anybody interested in getting something made, or getting the virtual copy, let me know and I'll hook you up.
 
#14 ·
You have to love people who identify a need, come up with a solution, and try to spread the knowledge.

Just keep in mind you are competing with things like this, and this, and this (my favorite), which all have the benefit of loads of field testing, R&D, refinement, customer feedback, etc.

Then again it's a hunk of steel, not a suspension system. Can't be too hard to get right. Let's see some finished product!
 
#15 ·
Here is the result of the mill, it turned out beautifully. It took forever, but these are great cuts. The tow hooks will remain on there until the bumper is ready, so we bored out the holes on the hooks just a bit. The grade 8 nuts will be welded on soon, I'll post while I'm going through the rest of the project in a few weekends.
 

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#16 ·
I think you are doing a great thing. Even if this project doesn't turn out to be a money maker you are gaining valuable experience. I admire your ambition. America is the best country on earth.

Since you have access to a mill, why don't you start with a wider plate and cover the carved pumpkins mouth. Trim away the excess to match the shape of the crossmember. Perhaps that will prevent moisture from entering the recent repair and contribute to the repairs longevity.

On my Jeep the blind nuts are in the aftermarket bumper. If I had blind nuts on my X-member I would be unable to mount the bumper.

Wishing you the best, keep up the great work. L.M.
 
#17 ·
The crossmember is 3 inches wide and I believe that the curve is about an extra inch. I was considering cutting steel as 4 inches wide but I found this flat bar and it's significantly cheaper than buying flat stock.

I've found a welder a few miles from my house that makes bumpers (keeping the money not only in America, but locally), and I've made sure that my method will fit his bumpers. I also believe that it will fit Smittybilt bumpers, or any bumper that bolts to the frame with no blind nuts. That's a good point though because it would require a much longer bolt to go through two blind nuts.
 
#18 ·
First day welding ever (aside from two other times where I just put the wire on the metal and pulled the feed trigger), and I think it turned out really well. Lots of spatter, but there was some slag that came off with some chipping and brushing, which is a good sign. The earlier welds were terrible, but once I turned up the wire feed, I started to get a glimpse of the "stacked dime" look. Blind nuts are on, and I managed not to weld the bolt onto the nut, so it's good enough for me. It's not pretty, but I'm not very pretty either.

This was with a cheaper welder, and for the welds that really need to hold, I'll be using a nicer welder at a hotter setting with thicker wire.

Bumper order is placed. Ordered from a local welder with a tow rated trailer hitch, permanent D-rings, and Hi-Lift Jack lifting locations. Below is a bumper he has made in the past, which is the one I am getting plus the jack location.
 

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#19 ·
The first day went well. The fuel tank is out, and all of the lines are dried out and plugged up.

Here's what I did to remove the tank:
Disconnect the battery.
Evacuate the fuel rail by pushing the core of the valve by the engine valve cover, like bleeding air from your tires.
Place a jack under the skid plate, and take off the four nuts on the front and three in the rear.
Remove the filler hoses from the tank.
Lower the tank a little. Look for a hose connected to one of the vent tubes on the tank. A single line goes into a tee and splits into two. One (shown below) is short and has to be disconnected before dropping***. The other should be long enough to lower most of the way.
Before dropping the tank the rest of the way, disconnect the wiring plug. It's about a foot and a half of wire that should still be on the tank.
Lower the tank and disconnect the two lines going to the fuel pump and sending unit, be sure to mark which is which. I tied a string around one line and the tube on the pump it went to.
Fuel tank straps can be left on until this point. Mine were already disconnected so that made the job a little harder.
Run compressed air through the lines, and catch the fuel that spills out. Then plug them up, and I gave it overnight for the vapors to vent out.

I then hosed off the skid plate and rubber pad, and washed off the top of the fuel tank. I planned on buffing out the skid plate, but it's made up of some horrible combination of mud, rust, road grime, and metal (we all know this), so I decided just to weld it back together and use it for now until I get some fuel tank armor.

Today I'll be doing the cutting and tack welds to get it ready to take to a pro welder. I've determined to bolt the angle iron being used as a brace to the frame, and have a good welder take care of welding it to the bracket.

All has gone very well so far, especially when you compare the scale of this project to the scale of other projects I've had extreme difficulty with.


***I had a vapor leak prior to doing this, and I think it's because somebody has dropped this tank before and only connected the longer hose to a vent, because it's easier. I hope this solves it.
 

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#20 ·
I'm just impressed with how on-schedule you are! I make plans all the time, but then life gets in the way.

For example, I have front leaf springs sitting in the garage. The rear leaf springs are on the Jeep, but the fronts are just sitting in the garage. They've been there for almost a year!

Good job, and keep us posted, you're doing great!
 
#21 ·
I've modified my schedule a bit, but I think it's still going to take the same amount of time.

Today I cut up the passenger frame and welded that in. That's a little more work, considering I had to fix the actual frame. I welded two pieces of angle together, and welded it into the frame. That part looks great, and I have no doubts about its strength.

The angle bracing the bracket to the frame is iffy. The angle is on the bracket very well, and I have no doubts about it. I'll make some more passes and maybe add extra metal to make it more sturdy. I wanted to bolt it, but it's a bad angle and all of the heavy work I've done has been with a mill, so I've gotten lazy with using a hand drill.

Still need to look at the top gap in the crossmember, but it's not a part that needs to be incredibly strong.

So now, I'm doing one side a day instead of cutting and marking one day, then welding the other day.
 

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#23 · (Edited)
The frame I thought was the "good side" turned out to be the worst. When I was prying out the old metal, the frame warped and twisted and about a pint of crud fell out. So I put the fuel tank back in, and went up to a friend of my dad's who is a welder, and he taught me how to use his professional Miller MIG welder.

After I had given up for the day on the frame, I decided to weld two screws together for my exhaust hanger that has been missing. Whatever works.

We plated the bottom gap, then welded in a square piece of steel I had made. That fixed the frame.

Then I did what I have been doing, and welded the plate onto it with some angle bracing it to the frame.

P.S. For some reason my photos seem to be in the wrong orientation. The files themselves are portrait, but they came out landscape.
 

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#24 · (Edited)
Learning to weld went really well, and the temporary tow hooks have been tested. They held up perfectly. The driver side will be ground down and painted within the next day.

Bumper should be here in a week.
 

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#25 ·
Finally! The finished product! The bumper feels very sturdy, and is well-built. I got a hitch receiver, D rings, and a Hi-Lift jack lifting location to make the jack safer. I used white Rust-Oleum paint/primer, then used flat black Rust-Oleum automotive paint. It lined up nearly perfectly, but I can tell that I warped the passenger side bracket when I welded it. I put all four bolts in on one side, then jacked up the other until it fit.

If anyone is in south-central Ohio and wants the name of the welder, PM me. He took a few days longer than expected, but the product is amazing and worth the wait, especially for the price. It's 1/4 inch steel I believe.

Here are the photos. I don't plan on towing anything more than a bike rack or utility trailer, so the ball is just there to deter tailgaters or to take out the ball and use as a recovery point for other vehicles. This same ball hitch was in my dad's old Tahoe and totalled a kid's Mustang who was following too closely (not a scratch on the Chevy), so I hope it will add some protection.
 

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#26 ·
Congratulations!! With that kind of motivation and dedication I am sure you will go far in life.
Stay away from drugs, booze and gambling and you are a sure case for success.
A quiet word of advice, the EZ lift jack is not ideal for lifting the Jeep for things like changing tires. It is not very stable. You are better off using the factory jack and a couple blocks of wood. The EZ Lift is for getting you unstuck or getting a corner up far enough to shove some rocks under a tractionless tire.
Wishing you all the best, L.M.
 
#27 ·
Thanks for the kind words, I've learned more in 6 months of owning a Jeep than most people care to learn in their entire lives. I'm just always open to trying something, and everything *knock on wood* so far has gone well except a brake job in the first week of owning it.
 
#32 ·
Part II: the Sequel is coming soon to theaters near you...
 
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