M927A2 / M939- Strictly reliability upgrades and modifications.

rbr0203 · Aug 8, 2018

I've been searching this site for good modifications. I have found plenty of mods that i will try when i have the money and the time. My question is if you were to try to make your 5 ton more reliable, more bullet proof, what would you do? I assume we would all try to change all the fluids, possible battery change, and inspect wires for shorts and such. However, i know most of the gentlemen here have lots more experience and screw ups over the years to provide much needed wisdom. Thanks in advance.

:grd:

NDT · Aug 8, 2018

Replace the humpty dumpty transfer case with something less of a ticking time bomb.

simp5782 · Aug 8, 2018

More power = more stress of weak components. As NDT said, the transfer case is the weak link. Any engine upgrades will take that power right out on that. Heat is the killer for the transmission. Bypass the heat exchanger and run a total air to air system for summer or towing but keep the heat exchanger for winter time in your neck of the woods for faster warm up times for driving.

Oil Filter bypass systems are very helpful with keeping contaminants like water and fuel out of the engine. They have a built in heater. You will find little quirks and what not to improve your truck to your liking. I can get in the drivers seat of mine and do 14 hrs straight and never get out of it, but i get in one of my other ones and im irritated with it in 5 mins. My 923 is highly modified. It is suited for what i want and what it needs to handle. I have upgraded the transmission, transfer case and drivelines before i am doing the motor swap so I didn't put too much power under the hood just to spend time blowing everything else apart when they are still good useful parts.

Someone suggested me leaving my 939 transfer case in until after the big cam swap and if it blows it blows. Why would i blow a $1200 transfer case when the replacement costed me $100 and i could sell a known good one.

rbr0203 · Aug 8, 2018

NDT said:
Replace the humpty dumpty transfer case with something less of a ticking time bomb.

Yeah so i kinda figured that out when i was moving it to a better storage location the other day. Ive driven these a couple of times when i was deployed but never as the primary driver. Little did i know that the transfer was already in low (did a small three part turn with it too, i know, know never go in reverse in low but i didnt know it was in low). I start going down the road and i couldnt get it above 30 mph. So i pulled over into a grocery store parking lot to figure out what was the matter. Ive never done anything with switching from high to low and visa versa. It didnt engage for the life of me and took several tries. finally got into high and low and behold i could get to 50. what a pain.

rbr0203 · Aug 8, 2018

simp5782 said:
More power = more stress of weak components. As NDT said, the transfer case is the weak link. Any engine upgrades will take that power right out on that. Heat is the killer for the transmission. Bypass the heat exchanger and run a total air to air system for summer or towing but keep the heat exchanger for winter time in your neck of the woods for faster warm up times for driving.

Oil Filter bypass systems are very helpful with keeping contaminants like water and fuel out of the engine. They have a built in heater. You will find little quirks and what not to improve your truck to your liking. I can get in the drivers seat of mine and do 14 hrs straight and never get out of it, but i get in one of my other ones and im irritated with it in 5 mins. My 923 is highly modified. It is suited for what i want and what it needs to handle. I have upgraded the transmission, transfer case and drivelines before i am doing the motor swap so I didn't put too much power under the hood just to spend time blowing everything else apart when they are still good useful parts.

Someone suggested me leaving my 939 transfer case in until after the big cam swap and if it blows it blows. Why would i blow a $1200 transfer case when the replacement costed me $100 and i could sell a known good one.

What would you say is an acceptable level of horsepower without issue? id eventually like to add more for towing a trailer and truck. I havent looked into the trans oil bypass yet so ill have to look into it. i also didnt know that the oil filter bypass had a built in heater, any suggestion on where to look for that? I plan on trading out the seats with leather aftermarket ones. I was looking at the gauges and lights, why would anyone paint over the indicator lights near the gauges? I took them off and all of them were originally clear. How did you upgrade the transmission, transfer case, and driveline if you dont mind telling me?

simp5782 · Aug 8, 2018

rbr0203 said:
What would you say is an acceptable level of horsepower without issue? id eventually like to add more for towing a trailer and truck. I havent looked into the trans oil bypass yet so ill have to look into it. i also didnt know that the oil filter bypass had a built in heater, any suggestion on where to look for that? I plan on trading out the seats with leather aftermarket ones. I was looking at the gauges and lights, why would anyone paint over the indicator lights near the gauges? I took them off and all of them were originally clear. How did you upgrade the transmission, transfer case, and driveline if you dont mind telling me?

My drive lines are 4in diameter shafts. Much bigger than 5 ton shafts.

I have some threads on the cat 7155 swap and the oshkosh transfer case swap. The cat will not mate to an 8.3l truck though

You can get on up around 330hp and you will be fine. Add a bigger transmission cooler and maybe a transfer case cooler.

The oil filter bypasses are from puradyn and on Ebay for cheap.

Sent from my SM-G965U using Tapatalk

rbr0203 · Aug 9, 2018

simp5782 said:
My drive lines are 4in diameter shafts. Much bigger than 5 ton shafts.
I have some threads on the cat 7155 swap and the oshkosh transfer case swap. The cat will not mate to an 8.3l truck though
You can get on up around 330hp and you will be fine. Add a bigger transmission cooler and maybe a transfer case cooler.
The oil filter bypasses are from puradyn and on Ebay for cheap.
Sent from my SM-G965U using Tapatalk

are the drive lines / shafts hollow or solid, if hollow what thickness are the tubes walls? what would you suggest i and others look into for a trans and transfer case with you experience? thanks for the heads up on puradyn.

rhurey · Aug 9, 2018

more reliable, more bullet proof

beyond "change all fluids"

Thinking of all I have done...
Coolant filter
Block heater
Service air drier'
Multi-bank battery charger
Adjust transmission modulator
Check axle vents

rbr0203 · Aug 9, 2018

rhurey said:
beyond "change all fluids"

Thinking of all I have done...
Coolant filter
Block heater
Service air drier'
Multi-bank battery charger
Adjust transmission modulator
Check axle vents

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axle vents makes sense and i didnt think of them. come to think of it is there parts on the vents for the fording package?
dont even know where to look for the air drier yet lol

this was attached to the green line in the cab, looks like a mini air/water separator. However, its leaking air like a sieve.

simp5782 · Aug 9, 2018

rbr0203 said:
axle vents makes sense and i didnt think of them. come to think of it is there parts on the vents for the fording package?
dont even know where to look for the air drier yet lol

View attachment 737428
this was attached to the green line in the cab, looks like a mini air/water separator. However, its leaking air like a sieve.

That is For the ctis as a water catcher.
Air dryer is back on the frame.

Most of the axles just have check valve vents. We normally put hose barbs in em and run a hose up to clear any terrain

Driveshafts are hollow. They are heavy enough as they are. You couldn't lift a solid driveline on a 927. Especially the front driveline

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rbr0203 · Aug 9, 2018

simp5782 said:
That is For the ctis as a water catcher.

Is it supposed to have air leaking out the base? I feel like it shouldn't

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simp5782 · Aug 9, 2018

rbr0203 said:
Is it supposed to have air leaking out the base? I feel like it shouldn't

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No. Pull it and clean the bottom of it out and make sure it isnt cracked or stuck open. or disable your ctis

71DeuceAK · Aug 18, 2018

Following this, as strictly an XLWB M939 owner as of now. Of course, these things all apply to any M939...

silverstate55 · Aug 18, 2018

rbr0203 said:
axle vents makes sense and i didnt think of them. come to think of it is there parts on the vents for the fording package?
dont even know where to look for the air drier yet lol

View attachment 737428
this was attached to the green line in the cab, looks like a mini air/water separator. However, its leaking air like a sieve.

As Simp5782 said, take it apart & either clean or replace the little O-ring at goes on the base (drain petcock). The O-ring is either dried/cracked or in need of some rejuvenation with some silicone grease.

rbr0203 · Aug 18, 2018

silverstate55 said:
As Simp5782 said, take it apart & either clean or replace the little O-ring at goes on the base (drain petcock). The O-ring is either dried/cracked or in need of some rejuvenation with some silicone grease.

Unfortunately it's leaking out the bottom piece. Looks like it was broken off or the release was gone. i purchased a small aluminum water separator from a bagger website. Ill install it and see how it works.

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M927A2 / M939- Strictly reliability upgrades and modifications.

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