XM818 transfer case swap.

[mattgunguy]

So I have this unfortunate condition where I do not have the ability to leave well enough alone. It is called "Gotta Screw With It Itis". I have decided that I don't care for the sprag system on the M818. It's been not the most reliable since I got to even work a few weeks back (gummed up & and rebulit the shift cylinder & poppet valves). So I've got this crazy hair up my rear.

I'm "hopping" to manage to install a NOS Axletech T600 transfer case out of a M1083 fmtv (I think). Got it for a whoooole lot less than a popular surplus site. So hopefully that's the expensive part of this project. Sourced new drive shaft flanges from my local driveline shop. Unfortunately my searches on here haven't yielded much useful info on this particular unit. So I'm still working on the finer details.


Axletech info:
http://www.axletech.com/na_en/products/product1.php?id=T-600

 

[ke5eua]

Correct me if I'm wrong but the FMTV series is a constant front drive engage. As stated in the literature you provided it isn't full but at 32% still providing power to the front axle.

I'm not trying to discourage you on this but I don't see the benefit of this over the sprag when you can do the mwo and add an air switch to fully disengage the front axle just like on the 939 series.

Edit:

Besides air operated low / high range what other benefit are you looking for? Your final drive is going to be higher than the stock sprag transfer at 1:1 on the rear output and 1.063:1 on the front.

Ref: http://www.steelsoldiers.com/showthread.php?21343-T-138-T-case-gear-ratios

DESIGN DESCRIPTION	RATIO COMBINATIONS	INPUT TORQUE BY RATIO Lb. Ft. (Nm)	INPUT/OUTPUT SHAFT DISTANCE Inch (mm)	PROPORTIONAL DIFFERENTIAL RATIO (OPTION)	OPTIONAL PTO. ACTUATION (OPTION)
3 Shaft	2.45/1.0 1.93/1.0 In High Ratio (1) 1.38​	2,950 (4,000) 3,685 (5,000) 5,150 (7,000) 4,610 (6,250)​	9.45 (240)​	32.4% Front 67.6% Rear​	Yes (Air)​

 

[mattgunguy]

In a nut shell. Just to do something different. I'm not exactly sure this is from a fmtv. Going to run down the p/n tonight. This looks closer to some of the MRAP's we had. But I never got to mess with those much before I got out. Yes I do believe a fmtv is a full time case.

 

[ke5eua]

I edited my post, but be aware you are going to run into ratio differences that are going to take away your top speed. Yes the FMTV's are full time, spent my first deployment behind the wheel of one everyday on route Tampa.

This should be neat either way.

 

[mattgunguy]

Lower top speed. That'll make my wife happy. Says I drive to fast anyways. If I can still do 45 I'll be happy. That's all I do a deuce too.

 

[mattgunguy]

Try fitting a T138 transfer case in the trunk of a Nissan Altima

 

[ke5eua]

How do you plan on engaging the transfer to full time front? I remember we would press the mode button on the Allison panel to put the transfer in full front drive.

What about going between high and low?

Seems everything was done on the Allison panel.

 

[mattgunguy]

The feller I bought it from did a few YouTube videos showing how to air shift everything. So at this point I'm "planning" on deuce style air switches. If not, it's back to the drawing board. The air shifting also throws me off as to what exactly this is. Because I was under the impression that the fmtv is controlled by the transmission. Air shift switches would make things much simpler.

Do a YouTube search for t600 transfer case to see his videos. Be warned though. He didn't do one long video, it's a bunch of short ones.

 

[ke5eua]

Pretty neat. I like the PTO option. I guess everything will be easy to do then, have several air switches for multiple configurations, lol

 

[mattgunguy]

Hopefully if not simple, maybe somewhat straightforward. Got way to much to do in a short time period. The kamo rally is in October. Between now and then I've got to get this done, do the crew cab on the m35a2, get the cattle car converted to a camper, fix my wife's Bronco, 2 car shows, 3 birthdays, & a wedding anniversary. So no free weekends for 6 months.

 

[ke5eua]

Wow busy busy. I thought I was rushing myself redoing my 818 in time for the ss ga rally, and I don't do anything else.

 

[swbradley1]

I'd like to hear about MWO that converts a M809 series sprag over to air shift?

 

[mattgunguy]

I'm not aware of one. Just the inline air switch modification some people do. Thought about doing that one myself, but I figured I'd forget to flip a switch at the right time & break something. So I searched around the forums & decided to go with the T1138 case swap. Started to hunt down a case. Blasted things are expensive & outside of my budget for this realistically. Found this one fairly locally cheap. Assuming my driveline guy comes through on the price he quoted for the XS flanges and drive shafts, I'll be into this for about 1500 total. Could have waited & gotten a 900 series case, but I do like to do stuff different & maybe this'll be of help to someone else.

 

[ke5eua]

I'd like to hear about MWO that converts a M809 series sprag over to air shift?

Let me search that for you...

http://www.steelsoldiers.com/showth...&highlight=mwo&p=922782&viewfull=1#post922782

 

[defbob]

I have a T600 t-case and 3 matching driveshafts being shipped to me. They were used in MRAP vehicles. The one on ebay is from a BAE Systems RG31. I have a set of Axletech 4000 axles out of one as well. The yokes are unique and take a 1480 ujoint.

 

[mattgunguy]

I have a T600 t-case and 3 matching driveshafts being shipped to me. They were used in MRAP vehicles. The one on ebay is from a BAE Systems RG31. I have a set of Axletech 4000 axles out of one as well. The yokes are unique and take a 1480 ujoint.

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Awesome. Been looking at some just like those. Been thinking of another project for them.

Thinking a 79 bronco, with a 4bt or 6bt cummins with MRAP axles, wheels, and 16.00-20 goodyears. Hmmmmmmmmmmmm. Might be time to sell some stuff.

 

[defbob]

If you get the narrow ones like mine (from a BAE Systems RG31/33), make sure you get new ones in the crate. The used ones have a chance that they had seen mines and may have kingpin damage. The wide ones had redesigned inner C's and are good either way. The rotors are only 1.25" thick, just like 1-ton Chevy and Dodge trucks, so adapting hydraulic calipers is easy. I am new to these, but here is some info I have gathered. These are the differences between the two styles available from surplus. Narrow (BAE Systems' RG31/33) and Wide (Force Protection's Cougar).

Narrow axles (like mine);
85" WMS
33" Spring perch width
5.64 overall ratio (1.58 R&P, 3.55 planetary)
Air locker (air to release)
CTIS
Smaller yoke that matches the surplus T600 t-cases and driveshafts

Wide axles (from Cougars);
90.5" WMS
34" spring perch width
6.84 overall ratio
Air locker (air to release)
no CTIS
larger yoke that does not match surplus driveshafts (the smaller ones are available on surplus, loose)

 

[mattgunguy]

Me thinks me wallet is going to hate you in the not so distant future. Have to deal with some ex-wife drama first

 

[defbob]

haha. The axles are cheap... it's the projects it encourages that are not...

 

[defbob]

My T600 t-case just arrived today. I'll be able to take measurements for anyone later tonight.