My m925a1 build "Brutus"

[muthkw25]

I decided to take the plunge and enter the 5 ton world. Had m35a2s and variants for 10 years and wanted a 5 ton. Came across a nice m925a1 back months ago and decided to start a new build. His name is Brutus. Truck came with all led lights minus front side markers and spin on oil filter adapter. Drove it 30 miles home w/I any hiccups.

Plan is to go through all routine maintenance (all fluids, filters, grease.
New windshields, wiper arms and wiper motors
Fix passenger door hinge,
Sandblast inside of bed with bedliner applied
Marine corps forest green pain (34052)
16r20 tires
Led fog lights
Coolant filter
Mrap radiator
Tmg air filter basket and filter
6" donaldson snorkel
Aftermarket muffler
Hardtop
Pyrometer
Dual fuel line mod
Running the overhead
Methanol Injection
Spin on fuel filter kit or fass
Backup lights
Locking fuel cap, stainless fuel strainer
Locking door handles
Battery cut off switch
Soundbar in cab
12v inverter

Plan is to have truck ready for 2024 season. Following photos are purchasing truck and bringing it home

 

[muthkw25]

Purchase a strainer and had a portable sand blasters come out and work on the bed. Inside of bed had the worst rust. Took longer to setup then it did to do the job. I primed it with 2 coats and sprayed herculiner on surface with 2 gallons to seal the bed surface.

 

[muthkw25]

Purchased tmg air filter and wire basket for less restriction. Changed engine oil and filter. I also decided it was time to change the muffler.

I was looking for a different exhaust tone and went with a 14" body 7" diameter magnaflow stainless muffler. It's small enough to hide completely under the heat shield and when painted will look stock. I ended up cutting the upper bracket for the original muffler to run the stack straight up. Used 2 thread adapters that were 1.5" in length and it spaced it out perfectly. Used all original exhaust clamps. Definitely made a difference when driving. Between the smaller diameter air filter and the free flow muffler, the truck will pull hills at 1000 rpms and hold gears for a longer period of time with improved acceleration. This would be a good alternative and cheaper than a new stock muffler with better performance. Can still hold a conversation with passenger without killing your hearing but has a more throaty tone.

 

[muthkw25]

I decided it was time to put a Pyro in before doing any significant driving or performance mods. Truck barely gets to 900 degrees pulling hills. Exhaust is clean when warmed up and pulls great. No plan to swap any buttons out. Plan on leaving it as is.

As I looked at truck more, the radiator side tanks were leaking and looked like they had a few patch jobs. Decided to try and flush the radiator and see what was inside. After 24 gallons of distilled water I decided to go with the mrap radiator swap. Much cheaper option than a brand new or rebuilt stock radiator. Mrap radiator is much larger. My buddy helped me with the install. Used the original base mount for the stock radiator and drilled holes into the bottom supports on the mrap rad.

Then had a C channel build 45 inches wide, 8 inch bend on top and 8.5 inch bend that bolts to the top of the radiator and uses the original hood attach point. This way it can always be undone. Had a cross over pipe made and used all original silicone boots. Rad works fantastic. Added about 2 gallons at least of coolant capacity. While installing this did a block heater and a coolant filter with new silicone lines to inner passenger fender for ease of changing. Truck under full load never sees 185F for Temps. Lubbed the shutter stat with some air tool oil. Truck has yet to have the fan turn on. Takes a long time for this bad boy to warm up.

I noticed my crank case ventilation was actually vented back to the intake manifold. I decided to put a filter directly on the air compressor to keep any dirty oil or blow by from getting into the air compressor. I don't plan on fording water. Definitely changed the tone when the compressor turns on.

I also had issues with my headlights. I installed a new high/low beam switch and found one of my led lights were bad. Bought a brand new set and kept the good one as a spare and fixed the issue.

 

[muthkw25]

My buddy helped me with the dual fuel line mod. Noticed some more improvement in performance but drastic change.

Decided to add some armor lights and replace the halogen bulb with a LED replacement. It's a PAR36 bulb. They are used for landing aircraft. Very very bright. Have them wired to high beams. High beams is so bright it looks like daylight now. Highly recommend to anyone who wants additional light. They make a spot or a flood. I chose flood for my application. Best part is the base is grounded and you only need one jump wire. So I put the wire in conduit inside the frame and ran to passenger headlight.

Had one of the mirror rods in the mirror bracket break off from rust.

The lock mechanism for passenger door was shot. Ordered brand new. Door works great now. Removed the spare tire piece that slides inside and out. Had to use a 4ft-4" monkey wrench to free it loose. Sanded it down primed and painted and applied grease and reinstalled. Works great now.

 

[muthkw25]

Installed a 6" donaldson snorkel and cut 6" off the intake tube. Didn't want the snorkel 2 ft above the spare tire mount. After hard top goes on I will push down a little farther to get it as close to the hardtop to blend in.

 

[muthkw25]

Had a hiccup when doing overhead. When my buddy came up to help with the radiator, dual fuel line mod, and coolant filter, we did the overhead on the engine. As we got to the last cylinder, the feeler gauge broke and a piece went Into the engine.

We tried looking for it and couldn't find it. Called cummins and asked for any ideas, they said it could be in the block or it could be elsewhere. Drained the oil and tried using a camera and couldn't see anything. Tried using a magnet and going down between the rods without luck. Panic set in.


We then decided to remove the rocker box and the rods and remove the cam follower. After removing the rear cam follower and pulling the rods we could see the metal in the pan. That was a sigh of relief. My buddy and I then put a magnet down inside the block and fished out the piece of metal.

The next part is what became very stressful. After looking at the cam follower, we saw a gasket and called cummins and they told me there was 2 shims for the cam follower. Went down and picked them up and when we got back home, we could feel a significant difference in the shim thickness between what we bought and what was on the truck. Spent hours on the phone with cummins. Cummins was almost no help. The cummins shop Gave me only 2 shims, when there is a number of different shims for the nhc 250. There was no markings on the old shims seeing they prolly were not replaced since the engine was put in the truck.

I bought a micrometer and we measured the shims and came to 0.66. Well the shims I had measure 0.47 which If the shims are the wrong thickness it can throw the timing off and cause a huge issue.

The shims on the truck that measures 0.66 were not ones you could get for the small cam. And cummins wouldn't give me the shims for a big cam because it didn't match what their manual said. After arguing with them and telling them the block is the same, it's not an internal shim, it's external it shouldn't matter, they still wouldn't ship them.

So luckily I was able to secure 3-0.22 shims to get to the 0.66 I needed. We then were able to reassemble the engine and do the overhead. Sad part is the overhead was out of adjustment but not by alot. So we did alot of work that probably wasn't necessary. However, I did learn alot on this big roadblock.


1) make sure to have angled feeler gauges because spacing on rear cylinders is not alot even with cab jacked up.

2) Don't waste your time dealing with cummins. If you don't know what you need you have to figure it out yourself. I barely got any help from them and the manuals for the nhc 250 are not online. Luckily using the tms got me the torque spec and extra help I needed as well as asking a few in the hobby that run these trucks. So thank you to those that helped.

I can say truck runs better now then it did when I drove it home.

Photo taken after reassembly and got some nice sunset photos.

 

[muthkw25]

Replaced both windshields, new wiper arms and blades. Also got air motor wipers working. They were rusted from being in elements. After working them free they work great.

Last photo is Brutus's first tow. I sold my m35a2 and the driver didn't have proper equipment to load the truck and parked truck at an angle and got stuck in my yard. I told him I'll get him unstuck with the 5 ton and he doubted me and told me it won't move It. Truck didn't spin. It idled and pulled him out. Didn't miss a beat. Impressed with the m939 series so far.

 

[muthkw25]

Moved the axle breathers up to the engine compartment. Ran a separate breather for the front axle to the passenger side, and rear axles to driver side. Also added new monroe shocks and added 16r20s with hemtt wheels. Installed front led side markers.

 

[muthkw25]

Swapped all gear oil from axles, t case and trans axles and t case got 80w90.

Installed a napa spin for trans and went to amsoil synthetic powershift fluid 10wt. It's rated for Allison transmissions and has improved Temps. My trans had what looked like hydraulic fluid. Wasn't burned. Looked quite new. But I wanted to put a high quality oil in the trans. I have some friends that run it and have had great success. So far so good.

 

[muthkw25]

Cleaned the fuel tank out before installing the strainer and locking fuel cap. No algae luckily but did have some rust particles. Fuel sending unit doesn't work so I am installing a new sending unit as well.

 

[muthkw25]

Even after the shock upgrade, the front is very bouncy, I decided to do fluid balancing and added 1 gallon to each tire of straight antifreeze. Worked for me in the past. I did a half gallon up front and it made a big difference. 1 gallon hopefully should he enough to smooth it out. Truck with 16r20s still drives well. Temps are a little bit higher. But I maintain 50 to 55 without hesitation. Happy with the results. Plan on testing soon after Thanksgiving.

 

[hethead]

Replaced both windshields, new wiper arms and blades. Also got air motor wipers working. They were rusted from being in elements. After working them free they work great.

Last photo is Brutus's first tow. I sold my m35a2 and the driver didn't have proper equipment to load the truck and parked truck at an angle and got stuck in my yard. I told him I'll get him unstuck with the 5 ton and he doubted me and told me it won't move It. Truck didn't spin. It idled and pulled him out. Didn't miss a beat. Impressed with the m939 series so far.

No matter how much you think a 5 ton can pull in low gear... it can probably pull more.

 

[muthkw25]

No matter how much you think a 5 ton can pull in low gear... it can probably pull more.

It was in high. Not low to make it better

 

[muthkw25]

Went to start the truck and the truck volt meter went way into the red for overcharging. Turned it off and tried again with same results. Tried removing the Allen key plug and of course it rounded out. Decided since so many have trouble with these to go with a modern alternator and make it easy to get parts should something happen down the road. Went with a 21si. Got a pulley and 2 new belts coming. Should fix any issues or potential volt problems in the future. More photos to come.

 

[Superthermal]

Moved the axle breathers up to the engine compartment. Ran a separate breather for the front axle to the passenger side, and rear axles to driver side. Also added new monroe shocks and added 16r20s with hemtt wheels. Installed front led side markers.

Excellent job on getting Brutus up to speed with your attention.
I had a question about the quick connect fittings for the axles. I am guessing those are 1/8" NPT or 1/4" NPT to fit the axle housing? Yes I am lazy to go out and look myself.
I had thought to add a 2-3psi pressure regulator to a set of these connections to pressurize with a manual switch the axles, trans and t-case when attempting a deep fording to keep water out. I would do this with a switch to go from "open" to "pressurized" with a switch which would be similar to the deep fording kits the military offered. I had thought I would be using something like 3/8" fuel hose for the lines but the nylon you used here got me thinking I could do this for half the price or less.

 

[muthkw25]

Thanks Superthernal, it is 1/8" npt to 1/4" dot line. I like the brass or metal quick connect fittings oflvrr the cheap plastic ones.

You could try it and see how it goes. I know the military pressurized the trans and t case but didn't know they did the axles that way. That would be neat to try.

 

[SCM35A2]

Installed a 6" donaldson snorkel and cut 6" off the intake tube. Didn't want the snorkel 2 ft above the spare tire mount. After hard top goes on I will push down a little farther to get it as close to the hardtop to blend in.

Who did you order the donaldson snorkel from??

 

[muthkw25]

Who did you order the donaldson snorkel from??

You can try those military guys

I looked online and found it in the US all ready and didn't wait 2 months plus. I also got a 5" to 6" exhaust adapter with one clamp and works great.

 

[muthkw25]

Installed a new alternator. Old one was overcharging. Tried to remove the Allen key plug and it stripped out. Decided to installa civilian one instead. Fixed my issues. Didn't want any potential damage to the abs system or control box. Best part I can go to any automated store and pick one up and not be stranded. Easy install. Highly recommend for anyone looking to upgrade.