new M656 owner second impressions

[sangamon]

I'm still impressed with the nice ride. Yes, really. Compared to my Mog, the M656 ride is excellent.

The M656 will not go up my hill (probably 30-40 degrees) in 4wd. The tires just spin on the slick grass. However, in 8wd, no problem, up we go. We're in the rainy season right now (September-July), so I'll see if I can find a dry day to try 4wd again.

I'm going to look for a hard top, which is part of the arctic weather kit. It's interesting that the truck is designed to drive in 65 degree below zero weather with the kit.

I have the "Organizational Maintenance Manual" TM 9-2320-230-20, which came with the truck. I also bought the "Direct and General Support Maintenance Manual" TM 90-2320-230-34 and "Organizational Repair Parts and Special Tools List" TM 9-2320-230-20P. The manuals are excellent. If computer software manuals were that good, my job would be much easier. It's also nice to read a manual that hasn't been "corrected" into oblivion by Microsoft Word's spelling and grammar checkers.

I've never owned a military vehicle before, and I'm impressed with the apparent ease of maintenance and repair (although I haven't actually DONE any, yet). The repairs look like many of them are easy replacements of what the computer biz calls FRUs (field replaceable units). I suppose that it makes sense that you need to be able to repair quickly, when the bad guys are coming over the hill, shooting at you.

More later, but so far, so good.

 

[dk8019]

Very impressive truck, still very jealous here!

Enjoy it, and keep us posted on how it does.

 

[Stalwart]

There just isn't enough weight over those rear axles to get traction. I bet if you put 4-5 tons in the back it would go right up in 4wd. It is really weight biased to the front, especially with that big hurkin' winch and steel bumper up there.

I bet Bjorn's 757 wouldn't tackle wet grass without extra weight or 8wd.

 

[jhigh]

I am happy to see the truck found a good home. I only road i it once but it was fun. Still close enough I might get to see it again one day.

 

[cranetruck]

Sangamon, there is a fairly safe bet that you'll not find a hard top for your baby for a long time, you are lucky to have the original vinyl soft top. I made my own top after a year long search and finding only the frame for it.
Many parts were specifically designed for this vehicle alone, including engine, transmission, tires and all the little parts and they are hard to find (less than 500 were ever delivered to the Army).


If you don't know the history, it will make interesting research, they were all used with the Pershing 1A program and ended up in Germany, except for a few at the Ft Sill Pershing battalion. They were not required to swim and the cargo version was used without the bed sides, so having a complete M656 is even more rare.

If you happen to spot a tire or two, let me know, they are very special.

 

[cranetruck]

Sangamon, some pointers about driving on hard dry surfaces....

The bogies are coupled without a differential, so you should think about removing the drive shafts circled in the image below, before driving on hard pavement, especially the front, since the front wheels turn on different circles and at different speeds when turning.

The drive shafts are mounted with self locking "place bolts", which are expensive so don't lose them. This particular fastener is typical for the hardware used on these trucks, so get used to it. Cost must not have been an object at the time. When reinstalling, keep surfaces as clean as possible and torque to spec.

 

[Stalwart]

I'm not so sure I agree about removing the driveshafts. Unless you intend to haul 10 ton loads, tire slippage should take care of the problem. I have 8 vehicles that have no differential between axles and they survive by tire slippage alone. The drivetrain in the 656 is much more robust than that in my vehicles. Severely mismatched tire circumferences should be avoided though. I wouldn't want to run a new tire on one axle and a worn out one on the next. I'd recommend replacing all tires at once and occasionally make circumference measurements and rotate accordingly like I do on my Stalwarts.

 

[m-35tom]

the michelin 14.5R20 is almost an exact tire replacement. when i last checked soft tops were still available and in extremely good like new condition still in sealed bags. in 8 wheel drive they will go anywhere a tracked vehicle will.

 

[Stalwart]

They are about 3" smaller than the 395's he's running now, he'll loose some of his 60 mph cruising ability. His truck turns 2500 rpm @ 60 MPH. I never liked pushing that engine past 2500 rpm, the transmission shifts (@ full throttle) at about 2450-2500.

 

[cranetruck]

the michelin 14.5R20 is almost an exact tire replacement.....

There are some differences, the original 16-20 (16/70-20) are bias ply, not radial, for one thing. The Michelins are heavier and not as wide, they don't mount as easily on the 12-inch wheels (which is wider than recommended).
The originals are made to operate at lower pressure (30 psi highway and as low as 10 psi continuously off road, including on side slopes, where radials need higher pressure to survive).

The 16-20 low pressure, low profile tires were designed for this series of vehicles alone and I think it's worth the wait to find to correct tire. IMHO, it also shows respect for the designers/builders of the vehicles.

The 16-20 tires may very well have been some of the finest bias ply tires made. I'm saying that, because it's dang hard to find any information on tire design when it comes to actual engineering and rubber composition. I checked with a recapping company that used to recap tires (900-20 and 1100-20 NDCCs) for the military and at one time they mentioned that an extra ingredient was added to the compound as specified by the military...he couldn't tell me what it was..
Image shows the 16-20s on my xm757, as made by Goodyear at their Danville VA plant. The Michelins just don't look right either.

Edit: Added image of LF tire, which is a BF Goodrich recapped with date code REOR "5080". See how much fun it is to work with originals, codes, dates and lots of unknowns.

 

[m-35tom]

i don't doubt you bjorn, but the 16-20 tires that came on my m-757 with 1969 date codes were EXACTLY the same width and heigth of the michelin 14.5R20 and were easy to mount.

 

[cranetruck]

I don't believe that the army would have neglected the tires to a point that they were 20 or 30 years old before replacing them.
The "69" on the side wall is not the date, at the time the date code was a 3-digit number and the decade was not shown. Example in image below.

 

[m-35tom]

well the army didn't own it for a long time... when i bought it, it had been sitting in a yard for 18 years. it looked like the 1800 miles showing might have been accurate. still, the tires make the 1000 mile trip home

 

[roscoe]

Is this the same vehical or type as the xm410 e1? I was just watching a very good video on a Gama goat website with testing of military vehical mobility. The xm410 e1 looked very simiar to your 656. Very impressive truck on the video.

I just saw the 656 on the 2nd part of the video. Must be the big brother to the xm410 e1. Looks like a really cool truck.

 

[m-35tom]

no, that was a 2 1/2 ton truck not a 5 ton

 

[boomer]

I'm still impressed with the nice ride. Yes, really. Compared to my Mog, the M656 ride is excellent.

No comparison. The 656, is a Prime Mover!

 

[duncan]

I was going to ask the same thing about the differences between the 656 and the 757, but I think I figured it, One is amphib hauler and the other is a mover with 5th wheel, yes? Either way, I love seeing 8-wheeler trucks, theres something amazingly cool about all of them.

More pictures! It's a shame I'm in Europe, wouldve loved to drive by and do a side by side of the USA and USSR heavy haulers. Maybe one day if I get to fulfill my dreams of traveling up to alaska with my 813.

Keep them going!

 

[cranetruck]

Duncan, some images that will give you an idea of the differences. The weight distribution empty or loaded, is almost identical for both variants. The 757 doesn't swim, but will ford 4 ft of water without any preparations other than pressurizing the axle housings, brake drums and engine and drive train.

 

[duncan]

Now you've confused me. Which of those 8-wheeler trucks was the amphibious one then, if any? And are these two trucks from the same company (ford?), same chassis, engine, drivetrain? Or just two amazingly identical rare models?

 

[cranetruck]

M656 with bed sides up and w/cargo cover. The bed sides are sealed with pressurized air for swimming.
All built by Ford and less than 500 delivered to the army in 1969. About 1/3 were xm757 truck tractors.