41 Dodge Military 4x4

Truck history
Power steering
Buick 231 v6
SM465 tranny
Engine and tranny install
Drivetrain
Swing pedals
Hydraulic clutch
Brakes
Warn hubs
Gas shocks
Combat rims and NDT tires

Truck history: I bought the truck from a friends Dad in Idaho for $300. It was originally an open troop carrier, but was modified in the late forties with a 41 Plymouth cab and flatbed, but the running gear was still stock military. It was about a 6 hour ride from my house to pick it up. I rode my Suzuki Katana with hopes of getting the truck running and carrying the bike back on the flatbed.

The truck hadn't been run in about 5 years and after taking one look at it, I knew I wasn't driving it back. It had flat tires, rats nests in the seat and wasps nests in the cab. We pulled the truck out of the shed with a crawler farm tractor. We made a couple of attempts to jump start the truck, but decided it was too much work and would need to trailer it back to Seattle. We had a truck rented to bring back some stuff, so I rented a flatbed trailer and we loaded it up.

When I got the truck in my barn, the first step was to clean it up a little and then to get it started. It didn't take much to get it started, a new battery and fix an air leak in the fuel line and it fired right up. At that point, I figured I would fix it up and leave the original drivetrain. The engine was the stock 85 hp flathead 6, with a granny low non-synchro 4 speed. This tranny wasn't just non-synchro first, but non-synchro in all gears. That meant learning how to double clutch. Double clutching is pushing in the clutch, shifting into neutral, letting out the clutch, pushing in the clutch then shifting to the new gear. This process gets all the gears spinning at the same speed so they mesh when shifting.

At this point in my life, I was single, so I spent every spare minute for a few months working on the truck. I stripped off all the paint including sand blasting all the cracks and the cab interior. Next I did the painting. I tossed around military olive drab, but ended up with gray.

After I got everything done, it was ready to drive. At that point I thought it was cool that it was even driveable, but there were a number of things that needed improvement. There was a huge vibration at about 30 mph, so I had the tires balanced and got a steering damper. One of the rims was bent pretty bad, but a lot of weighs helped. The steering was loose, the brakes didn't work very well, it was gutless and I had to cross my fingers to get it started. But, I didn't expect much more, and drove it a number of times in the next year. One day, it just wouldn't start. After the battery had went dead a couple times, I decided to tear it apart and do an engine conversion.

Power steering: After everything was stripped off the truck and cleaned up, the first modification was power steering. The stock steering box mounted to the inside of the frame next to the engine with the output for the pitman arm sticking out of the frame. The pitman arm points straight down and attaches to a link that goes forward to the knuckle. I wanted to mount a power steering box in the same location as the stock box, use the stock pitman arm and linkage, and use the stock steering column. The first step was to find a steering box. Most of the boxes I looked at would mount OK, but the output turned the wrong direction (turning the steering wheel to the right would turn the truck left). There were a few years in the 70's that Dodge made a steering box with reverse gears. I think it had similar linkage as my truck. Like most everything else, I found one at the swap meet. But, someone had taken a grinder to the internal gears to try and take the slop out, so I had to get it rebuilt.

The stock steering box bolted to the inside of the frame, but for the new steering box I had to weld a plate to the frame that it could be bolted to. With the plate welded and the box mounted, the output stuck out of the same hole in the frame that the stock one did. The pitman arm fit on the new steering box, but the splines were tapered, and the stock ones were not. It was tedious, but I slightly tapered the inside splines on the pitman arm with a file so it fit on the steering box far enough to get a lock washer and nut on.

I wanted the interior of the truck to look stock, so I wanted to use the stock steering column. It needed to be shortened with a yoke on the end to connect to the steering box. I had some spare steering parts including yokes and a splined shaft. The splines on the shaft were removable, so I turned down the end of my steering shaft on a lathe so the splines slipped on, then welded them on. To keep the steering shaft centered in the steering housing, I made a bronze bushing.

The last step was to connect the steering column to the steering box. Because of the offset from the box to the column, I needed a u-joint on the end of the steering shaft, and a u-joint on the input to the steering box. I didn't have any yokes with the right splines for the input to the box, so I cut apart a yoke and another joint, and welded them together. I then made a short piece to connect the box to the column.

Buick 231 rebuild: Initially I was going to put in a 350 Chevy. I bought a 4-bolt main 350, tore it apart, and it ended up being a basket case. The engine was full of water and a couple of cylinders would have needed sleeving. A lesson I learned, never buy an engine you can't hear run, or at least check the oil and plugs. I ended up getting a Buick even-fire 231 for just about nothing. I liked the idea of a v6 better because the stock drivetrain was only intended for 85 hp, and I have heard stories about v8's and broken axles in these trucks.

The first step was to determine exactly what engine I had. I found a great web page on Buick v6's, and from the serial numbers I determined I had a 1980 or 81. The 231 odd-fire was only made in the late 70's, so I knew I had the even-fire. Now I knew the year, so I ordered a full rebuild kit from Northern including new .030 oversize pistons. After I already had the bottom end together, I found out that the 231's are externally balanced on the flywheel. The flywheel I got with the engine was from an odd-fire (its the big ~50 lbs one). I ended up getting it rebalanced for an even-fire motor.

After I got the engine started, it ran good at a higher RPM, but wouldn't idle. After messing with the carb, I determined I needed a new one. The stock carb is a Rochester Dueljet, and a rebuilt carb would have cost me about $220. A new Holley 350 cfm 2 barrel carb was the same price, so I ordered one, along with an adaptor from Summit Racing. The adaptor they sent me was wrong, and I found out (from multiple sources), the adaptor TransDapt used to sell, is no longer available. So, I grabbed a chunk of aluminum and made one in the machine shop at work.

In the next test drive, the engine idled great, but didn't have any power. I remembered I did not remove and plug the distributor vacuum advance for the initial timing, so I adjusted the timing. Now it runs great and has a surprising amount of power for a v6 in a heavy truck. With the original flathead 6, top speed was maybe 50 mph with a tail wind, but now it has no problem doing 60.

SM 465 tranny assembly: The first SM465 I bought was a 4wd unit. It was in pretty good shape, but missing a few parts. At that time, I didn't know there was a major difference between a 2wd and 4wd tranny, and I needed the 2wd unit (my xfer case attaches to the tranny with a driveshaft (divorced)). The main difference is the tranny main shaft. The 4wd shaft has a short 10 spline stub at the rear that mates with a xfer case. The 2wd shaft has a longer output stub with 35 splines for the u-joint yoke. I was lucky, and found a complete 2wd SM465 with a cracked case at the swap meet. I took the main shaft out of the 4wd unit, and used all the parts from the 2wd. Taking the main shaft out of the case isn't an easy task. Everything has to be done in the right order, and took a little while to figure out.

Engine & tranny install: The first thing I did was bolt together the engine and tranny to install as a unit. I had the Buick bell housing with the GM tranny mounting. An older SM420 would bolt right on, but the newer SM465 has a larger input bearing, so the hole in the bell housing must be bored larger. Because this truck has a divorced xfer case, I didn't have to bolt on the xfer case. At this point, I made the hydraulic clutch slave cylinder mount. It was easier doing it now, than waiting until the engine was in.

The length of the Buick v6 and SM465 is about the same as the stock flathead 6 and 4 speed, maybe a little shorter. I hung the engine in the frame and leveled it to determine where the motor mounts would be. Front to back, there wasn't much room to play with, but I wanted it within a couple inches of the radiator. Because of the power steering box, I had to move the engine about an inch towards the passenger side. Now it was ready to weld the motor mounts. I made the motor mounts from 2.5 inch square, .25 inch wall tubing. The tubing was welded to a plate, gusseted front and bottom, and the plate welded to the frame.

After the engine mounts were in, I had to make a support to hold up the back of the tranny. There isn't any kind of obvious mounting points on the SM465 case, and I was wondering how they are held up in a 2wd truck? In 4wd trucks, the crossmember probably bolts to the xfer case. I ended up making a mounting plate that bolted to the 3 bottom bolts that hold on the rear bearing retainer. The plate was made from a large piece of angle, so the bottom was flat. I bolted a rubber Jeep xfer case mount to the bottom of the plate to allow for movement. The rubber mount bolted to a cross member I made that bolts to the frame and drops down for the tranny mount. After everything was in place, I got the short tranny to xfer case driveshaft modified so it was a little longer and with a yoke that accepted the larger 3/4 ton u-joint of the tranny.

Stock Drivetrain: The frontend, rearend and xfer case are still stock. The ring and pinion ratio is 4.89, and I think the ring gear diameter is about 9.75". The rearend is full floating, which is nice for heavy loads. The xfer case is single speed, so there is just 1 lever for 2wd or 4wd. With the 6.5 granny low in the new tranny, I still get 32:1 gear reduction. All of the above had 50 years of grease and all needed new seals.

Swing pedals: The stock pedals went through the floor with the mechanical linkage underneath. I wanted a new dual master cylinder, and hydraulic clutch cylinder on the firewall, so I changed to swing pedals. I bought swing pedals at a swap meet, and I think they are from a Ford truck. It wasn't too hard to bolt in, but I had to lengthen the front mount to the dash, and make a mount for the steering column.

Hydraulic clutch: I have never liked mechanical clutch linkage, and in my opinion (especially for offroad), hydraulic is the only way to go. I found master/slave cylinders out of a Toyota Four Runner at the swap meet. The master mounted on the firewall with an adjustable rod to the swing pedal. The slave was a little harder to mount. I made a mount that bolted to the Buick 231 and held the slave. I used a clutch fork I had, but it was too short so I lengthened it a little. For the hydraulic line from the master to the slave, it is mostly metal line with a short piece of rubber for engine movement.

After I got it all put together, I found that there wasn't enough throw. To get the tranny to shift, I had to tighten the linkage so the throwout bearing was pushing on the pressure plate. So, to get more hydraulic throw, I either needed a larger bore master or smaller bore slave. The Toyota master had about a 5/8" bore and the slave 13/16" bore. I tried to buy a Toyota Landcruser slave with a 3/4" bore, but the part was discontinued. I ended up getting a universal Wilwood master cylinder with a 3/4" bore. This gave me lots of travel, but is a little harder to push. I got the master cylinder from a hod rod shop, and they also had universal slave cylinders with a 7/8" bore.

New Brakes: When I first got the truck started, I didn't get new brake shoes. They still had some pad left, but they had been soaked with brake fluid. I couldn't find any brake shoes locally, so I had them relined. The wheel cylinders were a standard size, so I just honed them and used new seals. I don't think the drums had ever been turned, so I did that mainly to get rid of the ridge on the outer edge.

Because of the swing pedals, I needed a new master cylinder. I used one from a late 70's Dodge truck. After bleeding the system, and adjusting the brakes, they work, but still have room for improvement. There is a kit available to install front disc brakes, which would be real nice.

Warn hubs: A very nice addition to the truck was a set of Warn hubs. I got them from a friend with a 41 that upgraded to a 3/4 ton frontend. With unlocked hubs, the ride at 60 mph is much smoother. Warn no longer makes these hubs, but new hubs are available from another company.

Gas Shocks: The stock shocks on the truck did not work at all, which made for a bouncy ride. When I switched to 9.00x16 tires and combat rims, the ride got much worse because of the extra weight. I had a set of stock gas shocks from my Jeep, so I decided to use them on the truck. The front Jeep shocks have a normal shock mount on 1 end, and a stud mount on the other. I made a small adaptor plate with 2 holes that bolts to the lower shock mount. I mounted the stud end of the shock in the other hole of the adaptor plate. For the top side, I welded a plate to the frame that has a bolt for the top shock mount.
Picture of front shocks.

The rear shocks were easier to mount. I just used a bolt with the lower shock mount, and for the upper, welded a stud to the top of the frame.
Picture of rear shocks.

Combat rims and NDT tires: Every stock rim on the truck was bent. The stock rims balanced ok, but wobbled on the road. I purchased 2 combat rims from Vintage Power Wagons, and 2 from a guy in Eastern WA. The 2 rims from Eastern WA still had tires mounted, so the first task was to remove the tires. Even though the rims unbolt, they were rusty inside, so I couldn't get the rim apart. So, I thought why not remove all the nuts, then fill the tire with air and the rim will pop apart. After a little bit of air, the first rim popped off. The second rim took more air, and when the rim came apart, the tire and rim jumped 6 ft. off the ground (I was about 50 ft. away). After the rims were disassembled, I sandblasted them to remove about 4 layers of paint. After sandblasting, I applied good rust primer and painted them olive drab.

I wasn't sure what type or size of tires I wanted. Originally, I was going to purchase a set of 35" Buckshot radials (I think QR78x16). But, the swap meet in Puyallup WA was coming up, so I wanted to wait and see what kind of deal I could get. At the swap meet, I didn't find anything the right size, until we were just about to leave. There was a set of 9.00x16 NDT tires with about 75% tread. I kind of wanted radials, but couldn't pass up this deal.

The NDT's actually ride pretty good. They are much better on the road than the 7.50's I had. Because the edges of the NDT's are rounded (compared to square like my 7.50's), they don't follow cracks in the road. But, one thing I don't like is the flat spots. It takes a few miles of a crappy ride for the flat spots to work out. I also haven't had them in the snow, which I hear they are pretty bad.

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