How to convert your Factory Hitch/Boat Anchor to thru bumper hitch.

[Robkc]

Yes we all know that aftermarket bumpers are pretty well thought out and in general are an excellent option to gain ground clearance. Slee makes a great bumper and as a replacement for the factory hitch Slee provides a surface mount hitch or in newer models a rather lightweight receiver style hitch that is not recommended to be used for towing.

So after only 1 year of wheeling this setup it is readily apparent that even the Slee hitch options are not ideal. The Slee surface mount hitches act more like a plow hook and I can visualize how absurd the factory hitch would be to wheel with.

So I started digging in a couple days ago. My Idea is to recycle a factory hitch to thru the bumper stout enough to use for recovering other vehicles with tow strap or trailering anything my engine/brakes are up to the task of moving/stopping.

(Edit - This is not a simple one job. Please read entire thread, re-read it and then evaluate whether you have the Welding/Fabrication skills to perform a similar customization. )

My bumper was an early Slee model without the hole precut through the bumper for a receiver tube so I needed to cut a hole.

Welded up the old bolt holes in the bumper. Made some plugs for them first so hopefully not welded to the cross member as well.

Blot flanges were cut off an old factory FZJ80 hitch, inverted and switch sides so that they cradle the frame rails rather than hang down from them. One existing frame weld nut bolt hole is used for both Slee bumper brace and the reoriented hitch flange. Additional holes are drilled and tapped.

 

[Robkc]

Main cross tube was cut in middle after removing the lower tube block for receiver.

Overall length was estimated using a new tube section in the middle. The pieces are then tacked together in place on the frame. A hitch extension through the hole in bumper helps locate proper position of hitch pieces.

 

[Robkc]

A 1/4" 2x3 angle welded to the top, flat plate welded to bottom of new cross tube to provide rigidity.

A 1/4" 3x3 angle is welded to the hitch extention piece at the bumper face to provide chain attachment points and will bolt through bumper and cross member.

All gussied up and ready to be bolted on.

 

[Robkc]

New hole drilled through the inboard side of hitch and extension to bolt the two tube sections together.

Of course none of this should be attempted without the necessary welding skills to keep everything together. A great big THANK YOU to my buddy 2FPower for assisting me in this area!

Why 2 tubes and all this work? The Slee bumper slips over the original rear cross member. If I ever damage the frame beyond repair I wanted to be able to unbolt the hitch and bumper to move them to a new rig. With face bolts and through bolt removed the extension slips out of the new hitch location and Slee bumper. Then hitch and bumper unbolts as per normal.

Another photo of finished project.

 

[Parsnip]

Awesome!

Curious, did you ever consider a setup that would let you store your drawbar/ball inside the frame when not in use? Like maybe plugged in from the inside?

 

[Robkc]

Good suggestion. Almost enough space between hitch and rear cross member if using a zero drop but need to have at least a 6 inch drop for my current trailer and only way to mount it without losing ground clearance would be drop horizontal and retaining pin vertical. To have enough space it would have to be inboard of the hitch and require scrambling quite a way under vehicle to remove. Rather use that available space for something like a secondary fuel tank or through floor storage bin.

 

[Huis Clos]

Great idea! well thought out and executed.

 

[tlin]

From Pic #1, Post #4 - does that thru-bolt on the back side serve as the single mechanical fastener keeping the hitch tube itself from being pulled out under load? If that's true, is that enough for true DOT-equivalent load handling (simply meaning is this strong enough to suit all your towing needs)?

Just "typing out loud" as I stare at the design, not trying to sound critical. I've wanted to do something similar thru my stock bumper and replace the drop hitch I've got.

Thx in advance......and well done!

 

[Robkc]

From Pic #1, Post #4 - does that thru-bolt on the back side serve as the single mechanical fastener keeping the hitch tube itself from being pulled out under load? If that's true, is that enough for true DOT-equivalent load handling (simply meaning is this strong enough to suit all your towing needs)?

Just "typing out loud" as I stare at the design, not trying to sound critical. I've wanted to do something similar thru my stock bumper and replace the drop hitch I've got.

Thx in advance......and well done!

Thank you!

The short answer is No that through bolt is not the only mechanical fastener keeping the hitch extension tube attached to the modified hitch. In post #4 picture 3 there are two goldish circles centered on either side of receiver opening that are bolts.

I put a lot of thought into this design and I will explain my method of bolting the hitch extension tube tonight then add some better pictures when I get home from traveling.

DOT hitch pins are equivalent to the shoulder material of a grade 5 bolt. Hitch pins are generally a 5/8" thickness in class III hitches ( 3500 lbs to 7500 lbs) and 1/2" in grade I and II hitches ( < 3500 lbs). The pins are cross drilled for placing a keeper through it so it can not fall out. I utilized only grade 8 fine thread nuts and bolts throughout my project. The fine thread requires a little less shoulder material of the bolt removed and provides additional friction due to the increased number of threads per inch of bolt to nut contact. This is similar to why a fine splined axle in the FJ40 is so much stronger than the coarse splined.

The through bolt is a 1/2" x 3 1/2" with almost no slop in the bolt holes. There is a grade 8 nut welded to the inside of the extension tube to allow snugging that tube to the side of outer tube. This snugging is to prevent rattle like is common for upper end hitch mount style bike racks. This also prevents the extension tube from shifting around and smashing the bolt threads which is the main reason DOT hitch pins are a snug fit in the receiver holes. There also is a nut on the outside of the outer tube so essentially the bolt is double nutted and a lock washer under the bolt head to prevent it coming loose. I did use a fairly long bolt to ensure maximum amount of shoulder material extending through the tubes. I added a few washers under the bolt head to keep the bolt from bottoming out at the shoulder to the welded nut by 1 thread.

I think the average individual would say that the above method should be sufficient to keep the extension tube connected to the hitch under any load conditions that the hitch would be subjected to. Our stock 160 hp engines just can't handle much of a trailer when you also consider that I am running 315/75/16's with stock gearing, armored front and rear bumpers, Metal Tech sliders, custom skid plates, etc.... Now when you consider that I plan to also use this a point to attach a tow rope for pulling someone else's vehicle if I can not find a way to get turned around to use the 12000 lb Warn which that is mounted up front... Well if it breaks under these conditions on the trail I don't think a lawsuit due to DOT regulations would be much of a concern.

However, being an individual that most often says doing good enough is just not the same as applying the theory of overkill I added some grade 8 bolts that are installed in a means that sandwiches lots of metal together at the bumper face. There are two 3/8" bolts going through the 1/4" 3x3 angle iron that is fully welded at all contact surfaces vertically and horizontally to the hitch ball side of the extension tube. These bolts go through the 1"4 angle iron, the 3/16" Slee bumper, the 1/8" rear frame cross member and a 3/16" backing plate that is welded to the inside of the rear cross member for the factory bumper mount surface hitches that are utilized in other parts of the world. I did weld new nuts to the back side of these combined 1/2" thick plates after removing the factory welded nuts for the 4 bolts that were too close to the through the bumper tube. Lock washers and blue thread lock was also utilized to prevent these bolts from loosening.

Wow, what a novel huh?

One last point. There is an awful lot of paperwork involved in getting any custom parts certified as DOT approved. My hitch design documentation here is provided purely for informational purposes and off road use only. No certifications are expressed or implied and anyone who attempts to make something similar does so at their own risk.

For comparison purposes here is what the Slee thru the bumper receiver tube components consist of.
http://www.sleeoffroad.com/installation/reciever_80_sof1059_v1.1.pdf

 

[Robkc]

Pic of the bolt on inboard end of tubes.

Pic of the face bolts.

 

[tlin]

Thx for the extra pics and info. Novel? Not really.....great detail supporting the thought and consideration you've put into this. Given my laundry-list of "to do" items, this one is simply being saved for later (being the only example of something I'd possibly like to do against my stock bumper so thank you again for posting/sharing - you've really hit the mark here IMHO).

Well done!

 

[cspangler]

Good write up. Great pics. Thx for the inspiration- planning something similar for my 80.

 

[Mud crawler]

Very good idea I'm going to consider making something similar for mine

 

[canman]

Very nice work, but if I had the coin, I would just bolt one of these on.

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