M1101/M1102 Trailers

It appears the .gov has been putting M1101 and M1102 trailers in auctions recently, and more and more are making their way into enthusiast hands.  Having purchased two myself from govliquidation.com, a M1101 and M1102, I’m putting down what I’ve learned so far.

What’s the difference between the M1101 and M1102?

Physically between the trailers there’s no difference. From what I’ve gathered, the bumpers on the tow vehicles, HMMWVs, were found too weak to tow the trailer at it’s maximum designed weight of 4200Lbs. So a different pintle/mount system came out for the HMMWVs came out, allowing the towing of M1102 units. Light HMMWVs were limited to tow the M1101, identical to the M1102, but weight limited to 3400Lbs.

M1102 and M1101 can be towed with heavy HMMWV M1097/M1114;
M1101 can be towed with light HMMWV M998/M1038.

In the non-military world, it should be no problem loading either to the maximum of 4200Lbs.

 

Modifying the electrical system.

The trailers are equipped with 24VDC lighting, “normal” as well as blackout. The system is wired as following:

Vehicle cable is routed directly to the terminal junction, located underneath the trailer.
In order to wire for 4 or 7 pin, simply remove the clamps holding the vehicle harness in place, and disconnect from the junction. I ended up cutting the connectors off of the harness and reusing them with a 4 pin harness. The wires are identified with a metal tag crimped on the wire by the terminal end, with the wire number stamped into it.

Pinout to 4-pin trailer plug is as follows:
Green wire = Right turn/stop light = 22-460 (Pin J)
Yellow wire = Left turn/stop light = 22-461 (Pin B)
Brown wire = Tail/marker/running lights = 21 (Pin E)
White wire = Ground, ground on existing ground stud.

Pinout to 7-pin trailer is as follows:
Pin 6, Green wire = Right turn/stop light = 22-460 (Pin J)
Pin 5, Yellow wire = Left turn/stop light = 22-461 (Pin B)
Pin 3, Brown wire = Tail/marker/running lights = 21 (Pin E)
Pin 1, White wire = Ground, ground on existing ground stud.

These 4 wires are the only ones necessary to operate the normal lighting system of the trailer. The rest of the wires can be ignored.

Lighting modification.

The tail light bulbs can be removed and the following bulbs can be installed, use bulb#1156 to replace original bulb 1683 and use bulb#67 to replace original #623.
The marker light bulbs can be exchanged as well, bulb type#96 seems to be the replacement. I have not confirmed this yet.

Later trailers use  multi-volt LED marker lights. Mine had some intermittent and weak ones, and I was able to find the following replacements:
Truck-lite 2″ LED, Yellow P/N#30250Y and Red P/N#30250R. Replacement modules run around $6, and I found them in stock at Ryder Fleet Products

Another option for the tail lights is the installation of a multi-volt Truck-lite LED unit, found here.

 MWO’s

There are 3 MWO’s that apply to these trailers: (MWO’s are like Service Bulletins or Recalls on cars).

MWO 9-2330-392-20-1 17 Aug 2001 modification is to provide a procedure for the installation of an upgrade for the original equipment surge brake actuator. It is replaced by an improved cast surge brake actuator with modified components.

MWO 9-2330-392-20-2 18 Mar 2003 modification is to provide a procedure for replacing the rivets used to secure the landing leg mounting bracket. Bolts and nuts will replace the rivets.

MWO 9-2330-392-35-1, Steel Draw Bar

The first two MWOs only needed for trailers built under contract number DAAE07-94-CR014, the original 1994 contract. The trailer’s contract number can be found on the trailer data tag.

I have yet to find or make PDFs with details of the MWOs, once I do I’ll post it here.
All I can say for now, is make sure, especially on the 94 contract trailers that the MWO’s are complied with. Compliance can be verified by looking at the MWO compliance tag, attached to the FWD side of the trailer.

Leveling the trailer.

The drawbar is quite high on the trailer, at 29.5″ much higher than most vehicle’s trailer hitch attachment.
It appears the HMMWV wheels can be exchanged with GM 8 bolt wheels, dropping the entire trailer down considerably using smaller tires.

Another option is a pintle riser on the tow vehicle. Not my personal favorite, as a trailer attachment that high up comes under a lot of lateral forces. Another downside of this is that some tow vehicles will be unable to open their tailgate with an extension that high.

Personally, I went with a lunette ring extension. I took the drawbar out, and had a 6″ U channel and filler plate welded in.

 

Other useful information:

The technical manual in PDF format. M1101 M1102 – 1995-10 – Maintenance & Parts List (TM 9-2330-392-14&P)

Interesting article on the problems the M1101/M1102s had, on US Senate level. M1101:M1102

 

M1102 pictures: