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1985 GM M1008 - GI Gyp: Part 1

1985 Gm M1008
John Cappa | Writer
Posted October 21, 2013

Getting gypped and moving forward with our M1008

Sometimes you just don’t get what you expect—nothing more true could be said about our latest project. We had been looking for a running and driving M1008 CUCV for several months. We stopped by Boyce Equipment in Ogden, Utah, scanned Craigslist and eBay and were beat out several times on bids that we put in at Government Liquidation. Eventually, an M1008 showed up online locally. It wasn’t exactly a bargain, but we decided to pull the trigger since we figured it already had a lot of the heavy-duty hard parts we wanted. This particular M1008 truck is an ’85. So, what is an M1008 military truck? It’s basically a mid-’80s 1¼-ton GM strippy pickup with a 6.2L diesel, TH400 transmission, NP208 transfer case, kingpin Dana 60 front axle, and a 14-bolt rear axle. Yeah, it doesn’t make much power since it’s a non-turbo engine, but it’s got a lot of desirable drivetrain parts underneath. The M1008 trucks also have 4.56 axle gears and a Detroit Locker in the rear right from the factory. This makes them perfect candidates for off-road project trucks with bigger tires. As an added surprise this truck had A/C, although it wasn’t blowing any cold air.

A quick test drive revealed what we thought was a minor shifting issue. The rest of the truck looked pretty solid aside from a hacked-out and rusty passenger-side rocker area. The truck also had the usual dented bed (sometimes they have a dented door, too), no doubt caused by some wacky military forklift operator who seems to have hit every M1008 ever discharged.

Anyway, we loaded our new-to-us truck on the trailer and brought it home, and it sat for a few weeks. We knew it had some oddball stuff on it, but we had no idea just how oddball the truck really was. We found the typical minor broken parts and hack repairs, such as a duct tape wing window, missing tailgate, and so on. Most of this stuff is easy to fix. One of the locking hubs wouldn’t unlock and the other wouldn’t lock at all. So we pulled ’em apart. It turned out that one hub was missing the slide gear and the other was assembled incorrectly, so it needs new locking hubs. We dove further into the axles and found that the rearend did not have the Detroit Locker that (nearly) all M1008 trucks come with. To our surprise, our truck doesn’t have 4.56 gears, either; it has 3.73s front and rear. It’s a little more freeway-friendly, although that’s not something we really care about because the 4.56 gears would be a better match for the tires we have planned. Oh well, we’ll just have to add a gear swap and lockers to the build list now.

Here is a sneak peek of our tires. We could have easily lifted the truck and cut the rear wheelwells to fit these 18/39.5-15 Interco Super Swamper Boggers, but we wanted our M1008 to stand out from a crowd of square-fendered trucks.

Next, we set to work on the A/C. It looks like an older aftermarket kit from Vintage Air. The A/C compressor clutch engaged fine and the fan motor worked (we could hear it running), but no cold air came out of the vents. The blower wheel was stripped. We simply pulled it apart, added a set screw and cold-blowing A/C was ours to behold. Oh, and the heater works, too. Interestingly enough you can turn both the heater and A/C on at the same time with different fan settings because they are completely separate systems, not that you would want to.

The tranny shift problem baffled us for a while. We found and replaced the broken VRV valve on the engine (it helps control the transmission shift points) with no change. We also fiddled with the vacuum modulator, yet the shift problem persisted. Eventually, we made a trip to the local transmission shop. A partial teardown revealed some loose and missing bolts in the valvebody. This also led us to believe that this truck has significantly more miles on it than the broken odometer claimed. Our transmission guy (familiar with these trucks and TH400s) said that it wasn’t the original TH400 transmission case. Getting gypped seems to be an ongoing theme with this truck.

To replace the dented bed we set out to look for an M101A2 trailer. The idea was to put the trailer bed on the truck. The M101A2 bed looks a heck of a lot cooler than the stock truck bed. It’s also a lot tougher (thicker steel), provides more ground clearance, a better departure angle, and the wheelwells offer plenty of room for bigger tires. We can’t take credit for the idea, though. A buddy allegedly stole the idea from another guy and is working on his own conversion on an old 2WD Dodge truck. We found an M101A3 (very similar to the A2 version) trailer locally and installed its bed on our truck. It’s an amazingly simple bolt-on swap that can be done in a couple hours, and we did it working alone without a forklift. The M101A2/A3 bed is made from thicker material than the factory bed, but it’s not double-walled so it’s about the same weight as the stock bed. Unfortunately, the M101A3 bed has its wheelwells pushed outward, making tire clearance a bit of an issue. For this reason we really would have been better off with an M101A2 trailer. We have a solution, but we’re still feeling gypped yet again. Keep an eye out for the next installment, where we’ll start spinning wrenches to improve GI Gyp’s off-road performance.

Step By Step

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  • Our ’85 M1008 turned out to be quite the oddball. Make sure you get what you are shopping for when truck hunting (unlike us). The A/C probably had us a little too starstruck to fully investigate our truck before plunking down the cash. Well, that and the fact that there were not many good M1008s being listed for sale at the time.

  • The M101A3 (pictured) has fenders that extend outward. These trailer beds require more wheel backspacing because of the inner fender design. The M101A2 is more desirable for a bed swap on a GM truck like ours because the inner wheelwells are deeper, but we’ll make do with what we have and run extra backspacing on our wheels.

  • We don’t recommend it, but we made the bed swap a one man job with the help of an engine hoist. Backing up close to the trailer allowed us to simply unbolt and slide the trailer bed forward over the truck framerails. A few buddies would have made the swap process a lot easier.

  • A pair of 16-inch-long, 2x2-inch, 0.120-wall pieces of square tubing support the front of the bed over the truck’s framerails. We drilled holes for four 5x1/2-inch Grade 5 bolts that sandwich the bed, tubing, and frame.

  • The support beams in the middle of the M101A3/A2 bed sit directly on top of the truck frame just like the factory truck bed. Out back we added some more 2-inch square tubing bed spacers and a 34-inch-long, 2-inch square tubing crossmember to allow the bed to sit level. Another four 5x1/2-inch bolts keep the back of the bed in place.

  • From the rear you can see the 34-inch-long, 2-inch square tube crossmember/bed spacer that sits on top of the frame. We also pilfered the military taillights and mounting brackets from our trailer and wired them into the truck. They hang a bit low for our tastes so we will likely move or replace them later on when we decide on what to do for a high-clearance rear bumper.

  • The M101A3/A2 wheelwells are positioned just slightly forward of the truck’s rear axle centerline. It’s only about an inch off, so we may correct it with some modified spring plates and perches to move the axle backward. The trailer wheelwells provide lots of room for bigger tires, though.

  • The factory side-mounted fuel tank was too low and dangly for a real trail truck. It’s also really ugly with the factory bed removed, so we yanked it off of the side of the frame.

  • We ordered a 17-gallon RCI aluminum fuel cell (PN RCI-2171A) and mounting brackets (PN RCI-7514A) from Summit Racing and installed it in the bed of our truck just behind the cab. This particular fuel cell is tall and narrow, so fuel starvation at angles will be a non-issue. If you need more or less fuel capacity, Summit has plenty of fuel cell size options ranging from 44 gallons to 1-quart. Our fuel cell came complete with a billet aluminum fill cap, a -8 AN fuel feed, return port, rollover vent, and a 90 Ohm sending unit that works with most GM gauges.


Vintage Air
San Antonio, TX 78266
Summit Racing
Akron, OH
Interco Tire
Rayne, LA 70578
Boyce Equipment
Ogden, UT 84401
Government Liquidation