BDGR's XM757 Rebuild Thread

[BDGR]

This is very optimistic of me, but I'm am going to try to keep a build/restoration thread going for the XM757 that I'm going to ATTEMPT to restore. Don't count your chickens. This will take a while.

Early this month, I stumbled across a vague facebook ad for "military trucks" in Fort Worth, immediately knew they were of the 656 family, and jumped on them. I regretted not saving a local M656 so I took the chance to fix that. The seller as a wood product company. The seller said they were the tractor versions, that the camo one ran at some point, but didn't know on the white one and were basically bare frame trucks. They got them from the neighboring county itself about 11~ years ago and planned to use them to pull logs out of the woods if they had to do that themselves. They never had to so the trucks just sat that entire time. Finally they were scrapping everything in the field they were stored in but refused to let them be destroyed so up for sale they went. The 2 conditions I was told was they had to go to the same home and they would not just be parted out. Basically one of them had to be put back on the road. Done deal, let's go.

I don't really want to talk about the H311 that was getting them home. Just...No.

Now they are stored at the local museum I volunteer at owned by fellow member TMOMW. I am crawling on them when I have the time and can stand the heat trying to assess things and make notes. Real work isn't going to start until temps drop. They are both XM757s tractors with winches from early 69. They are both missing their fifth wheels, rear decks, soft top frames, winches, bumpers, pintles, lights, and second fuel tanks. Since I have no bumpers, I have no bumper numbers. The camo one has the white trucks windshield. Lots of wiring and air lines have been cut. They need cleaned up to get some more info.

For now, I do enough info to make a plan with. I was told by the seller that the day before I showed up to pay and get the titles, one of their mechanics supposedly got the camo truck to start. They never figured out which one so I couldn't talk to the mechanic but they were adamant. Fuzzytoaster said he looked at them and said the white one's engine was DOA but the camo one has hope. That fits my insane scheme to restore the camo one as original as possible and then resto-mod the white into a truck I could drive without being afraid of breaking irreplaceable parts. I plan to start with the camo one and will be the focus of this thread. The white one will only be parts as a last resort unless I plan to replace said part anyways, but on the back burner for a few years.

The 3 goals for this winter work season aren't too big. 1st is document the entire vehicle with pictures to refer back to later. 2nd is pull and label the wiring harness out of the white one to send off with TM pages to get a new one made for the camo one. 3rd is to sand and repaint the camo one with its current camo scheme. The goal isn't to make it show quality, just nicer to work with rather than paint flakes EVERYWHERE. It's a stretch goal. I still have a few tasks for the museum that need to get done this winter.

I am going to try to keep as much as possible in this thread so if anyone ever tries this again, it's all in one place.

Thanks to Fuzzytoaster for the TM PDFs.

 

[BDGR]

It is FINALLY cool enough in CenTex to get some work done and we made some progress!

But that doesn't mean I haven't been busy on it. I have poured through the TMs noting PDF page numbers, printing and sorting entire folders and binders worth, filling notebooks, to get ready for work temps. After getting feedback from some coworkers and TMOMW, I got the electrical condensed to a 25 page color coded packet of essentials to work with out on the truck and to hand to any friend helping. I also made a full Electrical TM. My OCD was very happy but my office assistant helped keep me sane through the process.

This weekend, we pulled and labeled the Rear Harness that goes from the Toeboard (cab floor bulkhead I guess) to the fuel tanks and back to the tail. A lot of it was cut off and missing including everything on the passenger side. Some of what was left was barely hanging on. The only remaining tail light section was cut and dangling on it's own. We labeled everything we could noting where and how for when we unravel it as a guide for the new harness. It took about 5 hours to pull and there is at least one harness clamp I refuse to put back in. There is a clamp attached to the very front bottom of the cab between the frame rails blocked by the steering on the outside and metal hoses and the engine on the inside. It is the only cab mounted clamp besides the floor board connector which makes me wonder how or when in the clamp is even installed. Whatevs, I lived.

The next step was to lay it out, compare with the documents, and make a shopping list. My electrician friend is making the brave choice to teach me wiring so we will see how this goes. What's the worst that could happen? ...please don't answer that. 14 gauge wire, various connectors, loom, heat shrink, and some crimpers. He suspects the Toeboard connector is soldered together and not crimped? I need to look closer and go through the electrical section of the forums. I should be able to start remaking the harness within a few weeks. Hopefully. From there, one subassembly at a time.

One weird thing we came across was Wire 78. Wire 78 is for the Fuel Return Solenoid Valve and also the Right Hand Fuel Pump with Wire 79 being the Ground for both. With every diagram we look at, the return solenoid would only work when the right tank is selected. I will have to scan printed copies of the other diagrams later as the PDF isn't cooperating. Basic questions being when is a fuel return line used and why would it only be wired to one tank's pump? I have a diagram somewhere showing a line coming off the solenoid valve splitting to both tanks.

Plenty of lessons were learned. Take better before photos and a lot more of them and the same with photos after things are labeled. Overlap photos. Go overboard with notes because if I say I'll understand it later, I won't. Basically document better, both for my sake, and to share info if ever needed.

 

[G744]

Those multipin connectors are by Bendix.

Easy enuf to restore, unscrew the retaining back shell and weasel the rubber back along the wires. Be sure to salvage the wire markers for later.

If it is stuck, a squirt of DOT 3 will help things along.

If the wires will be cut, do so and pull them thru the rubber grommet.

Unsolder the wire stubs, and clean up the receptacle for later.

Most likely it is the same series as that found on headlight switches, bulkhead connectors, trailer recepts. That being said, it the grommet is rotten, you can source new ones in cutoff connectors.

As far as wire goes, I'd use type 1015 # 14 black stranded other than the rubber milspec stuff. I got a 1000' spool from Southwire to under $200 shipped.

As far as something to help loosen things up, Superzilla is the best I've ever used.

I had a XM656 some 30 years ago, unbelievable off-road ability. The military sometimes referred to them as "Mama Goats".

Traded it off for some AN/PVS-5 night vision goggles.

 

[Ajax MD]

I love the unusual, the esoteric and the historic. I'm glad you're taking on this project.
I've seen some weird, experimental stuff on this forum and it's awesome.

 

[BDGR]

Making very slow progress cleaning small parts while waiting on wiring parts. Bulk order of wire last paycheck. Bulk order of "Packard connectors" this check. Crimps and crimpers and misc next check. So on and so forth. Patience is a virtue I am told.

In the mean time, I have pulled the dog house off the white truck to clean up and 'restore'. I also pulled a small bracket off the back while I was at it. It's for the trailer electrical and air connectors. It was mounted under the rear cross member bolted through the angled supports. Judging by the damage and obviously sheered bolts, It was ripped off by the corner. On the camo truck, it was missing entirely and bolt holes were slagged so that will be "fun" later.

Since it is a simple flat piece, bent at 45s twice, with gussets on the ends, I will get a local welding shop make a few replacements for my two. I'm going to have to have several parts made like that over time like the windshield frame, bumpers, bumperettes and what not. The simple parts. If another 656/757 owner needs something, let me know so I can get enough made when the time comes to order the work. Otherwise I might stash a spare or two just in case.

 

[BDGR]

After 8 months of waiting, I finally got the title in for the white truck and still working on the camo trucks title. So I haven't died or given up yet. A M35A3 has also been bought for the Frankenstein path since the white trucks motor is for sure toast. I've been playing with that truck when the heat allows but since the trucks are parked in tall grass, the museum owner has halted all work until the rainy/cold season to prevent a grass fire.

Then everything changed. Long story short, I was contacted by a gentleman from the site that needed to rehome his M656 and obviously I couldn't say no. Two weeks and a large (but very fair) credit card charge to a local tow company later, its safely delivered and plans change again. I don't have a hoarding problem or anything. I can quit anytime.

HUGE THANKS to member jegjr for your generosity and kindness. My timeline for having a truck back on the road has shortened from many years to hopefully a year (hopefully. plans of mice and men).

The new truck is in better shape and is a better start than my 757s. It parked itself from where I got it. Fuel and air lines are all present unlike the 757s so if anything needs replaced, I at least of something to trace and use as a guide for bending new lines. The cab is in better shape and has a complete factory hard top. Some stuff needs replaced of course but it's a better starting point. Getting the first title was a huge delay because I don't want to put money in something not allowed on the road and then things snowballed, but hey, the delay worked out.

 

[G744]

I remember when these were in service.

The local units called the Gama Goat a "Baby Goat", the 656-767 were "Mama Goats".