Modern receiver hitch on an M37

[John Mc]

I've posted this on another forum, but thought I'd mention it here. I wanted to mount a receiver hitch on my M37. I did not want to replace the pintle hitch, since I like that look. I also did not want to hang it off the rear cross member of the truck, since the drop needed to get to a standard ball height makes a lever that would put quite a twisting force on the trucks rear cross member when towing heavy trailers. (I have 11.00R16 tires, so that lever would be even longer.) So I started searching for a receiver hitch which would mount to the frame of the M37, but which had minimal "drop", so as not to lose too much ground clearance. I regularly run my truck in the woods, driving through waterbars (basically, ditches across the trail installed for erosion control), so maintaining as much ground clearance as possible was my goal.

This turned out to be a longer search than I had imagined. The hitch manufacturers can't (or won't) search for a hitch based on the "drop". You have to tell the the year, make, and model of your vehicle, and they will tell to which hitches fit. Dropping in on local hitch installers was not much help either. They don't carry receivers in stock, they order them as needed for their customers, so browsing their inventory was not much help.

If you connect with the right tech support person at a hitch manufacturer, they can look up the drawings of a hitch and tell you the dimensions. The problem is that you have to tell them the model number of the hitch for which you want information.

I wanted the hitch's cross bar to sit under the truck's rear cross member, and as close to it vertically as I can. As it turns out, on my truck, you only need about 3/4" of drop from the top of the hitch's mounting flange (where it mounts to the truck's flange) to the top of the receiver hitch cross-bar in order to clear the "bulge" in the bottom of the truck's rear cross member - as near as I can tell, 3/4" drop will leave just about 1/8" gap between the hitch cross bar and the low point of the truck's rear cross member. (The pintle itself hangs down a bit lower, but with a hitch where the receiver tube mounts under the hitch's cross bar, this leaves plenty of clearance for the pintle.) Unfortunately, finding a hitch with that small a drop has proven to be very difficult.

The following posts detail the options I found.

[John Mc]

The option I found with the smallest amount of drop was a used hitch from a 2000 Jeep Cherokee: a Draw-Tite #75054. This has a drop of about 1.75", only about 1" more than required. It will bolt right up to the M37's frame with only a minor modifications: the outside of the mounting flange is a bit wider than the trucks frame, so you have to grind about 3/16" off the outside edge of the hitch's flanges for clearance where the rear leaf spring mounts to the frame. While the fit looked pretty good, I ended up not using this hitch, since it is only rated for 3500# GTW and 350# tongue weight (5000# GTW / 500# TW with weight distribution hitch). If that's enough for your towing needs, this is a pretty good fit with little wasted ground clearance and only some minor grinding to modify it from "off the shelf". 3500# was not enough for my needs, so I kept looking.

The second option is another hitch made for a Jeep Cherokee, the Curt #13084. It's rated for 5000# GTW / 500# TW (6000#/600# with WD hitch). I have not seen and measured this hitch myself, but it should bolt right up at least as easily as the Draw-Tite noted above (maybe easier, since it appears the flange is not as wide at the Draw-Tite unit - though I have not verified those dimensions). The drawback is that it appears to have slightly more drop than the Draw-Tite unit. If I am able to find out the amount of drop, I will edit this post with that info. I passed on this model as well. I could live with the 5000# GTW limit, but I wanted to minimize the loss of ground clearance. However, the option might work for someone who did not need the maximum ground clearance possible.

[John Mc]

Since I was not finding the hitch I wanted, I decided to order one and have it modified to fit the way I wanted.

I ordered a Draw-Tite 41536 receiver (it fits a 2001 Dodge Ram Truck, and I had heard that other hitches for this truck will bolt right on to an M37 just by drilling a few holes). It's rated for 6000# GTW / 600# TW (10,000#/1000" if used with a weight distribution hitch).

I brought the hitch to a local fabricator who did a bit of cutting and welding to move the cross bar forward about 2.5" and up about 2.5" to 3". He was careful to maintain the center-to center spacing between the left and right mounting holes on the hitch flanges. The rivets mounting the truck's rear cross member to the truck frame were drilled out. The hole was used for the rear-most mounting hole in the receiver hitch.

Here is what I ended up with:

Hitch Mod Rear copy.jpg (242.98 KiB) Viewed 1128 times

Hitch Mod3 copy.jpg (242.77 KiB) Viewed 1128 times

Hitch Mod Pintle detail copy.jpg (245.88 KiB) Viewed 1128 times

[Cal_Gary]

Hi John,
Mine had a receiver hitch installed, similar to yours, welded into the frame and was a bear to remove. I assume they added it after ripping out the rear cross member-another task still to be done but Bert hooked me up with a replacement some years ago.
Gary

[John Mc]

See drawing the fabricator made up of how he modified the hitch. Basically, he cut out the cross tube, leaving a bit of the sides connected to it as a square flange. Then cut out a similar square in the desired location and welded it back in.

I would suggest verifying the dimensions before actually cutting and welding, but it should be close as shown.

Drawtite 41536 hitch mods small.jpeg (249.07 KiB) Viewed 895 times

[John Mc]

If i were doing it over, I might avoid drilling out the rear cross member rivets, and just slide the whole hitch forward a bit on the frame and drill new holes. This leaves the rear cross member rivets alone, and makes the hitch fabrication easier: the way I did it, you had to match the width exactly to get the rivet holes to line up with the hitch (or slot the holes to allow some slop). If you go with all new holes, you can custom drill them to fit how your hitch actually ends up, and the frame is wide enough to allow for a bit of variation.