A new spin to an old problem

[my blood flows OD]

Ok so I got a m-813 with a sprag clutch transfer case... Yeah, I know .
but here is the new spin.
I wanna trade out the unreliable sprag case for one of the axle tech T-600 that are now flooding the market.
I don't expect this to be at all a bolt in but just wondering what you folks can tell me about these cases?
I can make a crossmember from scratch. That isn't an issue. I can adapt a disc brake from a ford escort or civic or whatever for an e-brake. That's not an issue.
will the driveshaft flanges fit?
they appear to be air shift?
im just looking for general knowledge before I buy one on these and find out it won't work or that they suck for some reason.

 

[Squirt-Truck]

So just why are you looking to change the good reliable case in the 813? What advantage are you looking for?

 

[my blood flows OD]

Why dump the T-138? Let me count the reasons. My sprag clutch case is not reliable. It has left me standard on many occasions. I'm the type of guy that likes the positive reassurance that my front axle is engaged before I attempt to climb a hill or rocks or mud hole or crush a car or hook bumper for a tug-a-war with another 5 ton.
I don't like getting in the middle of what ever I'm trying to do only to find that my transfer case didn't want to do its job today and now I'm stuck.
so now I have to wind it up and dump the clutch to wake up the sprags, and oh look now they want to cooperate, now that I stuck. Yeah not my idea of a great transfer case. Glad yours is working for your style of driving.

 

[simp5782]

Someone never finished theirs.
http://www.steelsoldiers.com/showthread.php?t=138729

If you want reliability go over to a 118008ru unit from the 915 series trucks. You wont ever hurt it.

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[sandcobra164]

I'd think there are plenty of M939 series T-1138 transfer cases that can be adapted much easier and provide you with an air switch front drive.

http://www.steelsoldiers.com/showthread.php?59654-M818-Transfer-Case-Upgrade-T-138-to-T-1138

 

[73m819]

Why dump the T-138? Let me count the reasons. My sprag clutch case is not reliable. It has left me standard on many occasions. I'm the type of guy that likes the positive reassurance that my front axle is engaged before I attempt to climb a hill or rocks or mud hole or crush a car or hook bumper for a tug-a-war with another 5 ton.
I don't like getting in the middle of what ever I'm trying to do only to find that my transfer case didn't want to do its job today and now I'm stuck.
so now I have to wind it up and dump the clutch to wake up the sprags, and oh look now they want to cooperate, now that I stuck. Yeah not my idea of a great transfer case. Glad yours is working for your style of driving.

Sounds like a simple cleaning will help solve your issue, dumping the clutch makes things worse and breaks things, instead of changing the transfer why not FIX the issue, the sprag in a 5t is almost bullet proof, almost 100% of the issues are from a air issue or the sprags are FULL of gunk.

 

[my blood flows OD]

I have drained the fluid and filled the case with diesel and ran the truck short distance with stop and starts to cause the fuel to splash around. Still no help. I'm sure the sprags are just not engaging all the time. I know if I dump the clutch the do engage so I don't think the issue is air.
And you are correct sir. It does brake stuff.

 

[Scar59]

My 813 had the same concern, sluggish/questionable engagement. I took Ron's (73M819) advice and drained the fluid, filled it with diesel fuel, short drive (no loads) to warm it up, drained the diesel ( and all the funk/dead bugs, spiders), service with fresh gear oil and it works like a champ. Engages when required. There is also a MWO mod to plumb a air-shift selector switch from a M35 to make selectable from the cab.
I've gathered the parts, just need the time. Maybe Ron will chime in.

Oh heck, Ron has chimed in. Thanks again Ron.

 

[sandcobra164]

I had a M818 out here that I picked up for a fellow member one time back when I was new to the M809 series 5 tons in private ownership. It had a strange issue with it's transfer case. It would never engage but every so often while going down the road, it would buck the whole truck as if one of the rear axles had dropped out. Never happened, the rear axles were always right where I last saw them. Took the air actuator apart and found nothing out of sorts there. Took the transmission tunnel sheetmetal out of the cab and the problem was obvious. Someone had installed a bolt in place of the breather on the poppet valve. It could never truly release the air captured on either side of the actuator on the transfer case so it sort of stayed in between. Once I removed the bolt, I was getting a nice clunk when going from neutral to reverse and the transfer was operational again.

 

[my blood flows OD]

One other thing is when I'm going up a steep dirt hill the rear tires will slip then the front will grab and then the rear slips agian causing a hopping action. I just thought it was the nature of these "part time" sprag cases.
Do you guys take your trucks off-road and know that your 6x6 work well?

 

[simp5782]

Why not just add a air solenoid operated by a switch to engage the sprag when you want to?

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[73m819]

When you do the transfer flush, this is NOT a one time thing, you need to flush as many times as needed till the diesel comes out like it went in , NICE AND CLEAN, you will be surprised how many flushes it takes and the amount of crap that comes out.

 

[red]

If you decide to swap the tcase out go with the T1138 from the m939 series 5 tons. It's a .73 high range gear ratio which will improve your highway RPM's.

 

[my blood flows OD]

I'm running 16:00's. I don't need more highway gears. haha! The poor truck struggles with what it has now.

 

[gimpyrobb]

I like the axletech cases, and they have a built in pto!

 

[simp5782]

I'm running 16:00's. I don't need more highway gears. haha! The poor truck struggles with what it has now.

Do you need me to send you a wake up kit for her?

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[my blood flows OD]

What is a wake up kit?

 

[simp5782]

What is a wake up kit?

35 percent up on the pump. Dual fuel line mod. Better forced air intake.

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[my blood flows OD]

35%? How's the egt's with that? What is the cost of the kit?

 

[simp5782]

I never see more than 1050 but you have all the power and fuel you need at 85 percent throttle so no need to get higher egts by wasting fuel with the pedal. I run 45 percent over stock towing everyday and i dont have an egt gauge. The pump, dual fuel line setup, and replacement return line is 1000 shipped both directions. 1yr warranty. I can tell you how to get more air to your engine and better cooling

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