Transfer Case options???

[vinny-socom1]

Is it possible to swap the sprag set up with something else? I really don't like this set up and was thinking there has got to be another option. Does anyone know what is in commercial HD trucks? I think a normal t-case would be great 6x6 low 6x6 high 6x2 nice..

Any help would be great!!!

Vinny

 

[Recovry4x4]

900 series transfer cases are air shifts.

 

[Ruppster]

I thought the front driveshaft could be disabled with a shutoff modification to the air line that goes to the transfer case that tells the sprag if it's in forward or reverse?

Ruppster

 

[Squirt-Truck]

Yep, simple air interrupt will place the 5-ton transfer front axle in netural. THe only advantage to haveing a non-sprag case is in SEVERE off-road use such as tree crossing. Otherwise it is superior to a full lock case in that you have 6x on demand and can operate on hard surfaces with a heavy vehicle. The sprag case is also MUCH safer in extreme downhill or slippery conditions, it will not allow wheel slip to defeat the steering.

So, they have 6x6 low, 6x6 high, and 4x6 with air interrupt. What more do you want? Just curious..

 

[Burgerboy13]

900 series transfer cases are air shifts.

 

[rebel_raider]

The only problem with the 900 t-cases is you can't back up in low range. It will crack the case.

 

[Sephirothq]

that is because of the extremely low gear ratio of the automatic.

i was looking at swapping a 900 series in my 800 series and from what i found it wouldn't be easy.

 

[rebel_raider]

Did not know that. Thanks for the education.

 

[vinny-socom1]

I have 3 t-cases all with issues in the sprag!!!! 1- locked up, 1-not locking up, and 1-coming unlocked when stuck..need I say more..

Vinny

 

[Recovry4x4]

Buy a deuce!

 

[vinny-socom1]

duces are to small....


Vinny

 

[D'cheat]

Any properly weight rated divorced t-case would work. Frightliner and Mack have awd rigs in their lineup. I really dont see why you cant swap one in. Fabricate a new crossmember, weld in the correct size u-joint yokes and be done with it. There are air actuated t-cases, Electronic actuated and good old lever actuated out there. Just depends on who you buy from. Heck, a google search comes up with quite a few dealers out there for just the t-cases alone.

 

[pctrans]

Vinny, are you sure the air valve on the tranny is functioning properly? Also, why not rebuild one of your t-cases, then you know it's right. Sounds like you have a good selection of parts.

 

[Trango]

Any properly weight rated divorced t-case would work. Frightliner and Mack have awd rigs in their lineup. I really dont see why you cant swap one in. Fabricate a new crossmember, weld in the correct size u-joint yokes and be done with it. There are air actuated t-cases, Electronic actuated and good old lever actuated out there. Just depends on who you buy from. Heck, a google search comes up with quite a few dealers out there for just the t-cases alone.

The killer with those is the price. Rarely do you see them for under $2000-$3000. Do let me know if you find one for cheaper.

Today, in fact, I'm drilling the frame on the new project to fit a M35 airshift case, since the peculiarities of both the 800 series and the 900 series cases kept me away from them.

Best,
Bob

 

[Burgerboy13]

The killer with those is the price. Rarely do you see them for under $2000-$3000. Do let me know if you find one for cheaper.

Today, in fact, I'm drilling the frame on the new project to fit a M35 airshift case, since the peculiarities of both the 800 series and the 900 series cases kept me away from them.

Best,
Bob

Just out of curiosity how much torque can a M35 air-shift handle?

 

[gimpyrobb]

On the swapping a 900 series in an 800, or M62(hehe), don't the 900 series have an over drive too? I though Werhring said thats why his Hawaii truck was so fast. Are the cases close enough to swap internal parts?

 

[rossM4]

ok, so is it possible to swap an air shift deuce T case into an M813 without it exploding into little pieces when I am in low lock and recovering a full size truck????? I guess my question is how strong is it and will it handle some abuse off road being attached to a cummins and all.

 

[kastein]

I have 3 t-cases all with issues in the sprag!!!! 1- locked up, 1-not locking up, and 1-coming unlocked when stuck..need I say more..

Vinny

so put the second case in when driving on the street, throw the first case in when you're offroad, and keep the other on hand for spares, problem solved

On a more serious note, I've been hoping I can find a Rockwell T138 for spare parts / rebuild around here somewhere. I hope to convert one to airshift and then swap it out and rebuild + convert the original. Just don't want to pull the original case and work on it, if I screw something up I won't have a vehicle big enough to go get a replacement case!

 

[Floridianson]

Just put in a 400BC 10 speed Fuller and the drop box/transfer from a 920/916.
That would be something to jump about and you KNOW who would help U.

 

[OPCOM]

Swapping the 900 series T-case in to the 800 series truck is a big, big job and there's no one way to do it best because of the differences in the case mountings and the angles. Mine had to be offset slightly from the transmission to fit but that is nothing to fear with the best u-joints.

I know I will have higher u-joint service due to this but it made several other things work well. The most important thing for u-joints is keeping everything in-line parallel to centerline. I might have done this differently but there were no detailed pictures posted or offered, so I can only assume this swap is not very common.

If you do it, please for your own help, study my job very closely to find ways to improve it.

The Rockwell T-1138 cases for the 900 trucks can be had for $2000 (ebay, rare)-4000 (memphis, all day).

The most valuable part of the unit is the casing due to them breaking in low reverse in rough military service where the driver is in a hurry with a fully loaded trailer and floors it backing up at which time the Allison transmission multiplies the torque and busts it. That is not supposed to happen because there is a mechanism on the Allison that won't let the driver get reverse when the transfer is in low. There is a switch on the transfer that sends this signal.

The case is very durable for regular use. The transfer is meant to be locked in high or low by air. unlock, shift, lock. One must not shift high to low on the fly, ever, without first putting the trans in neutral (not just pushing in the clutch, that is not neutral).

The front drive can be engaged or disengaged by air at will, but I won't be using it except rare offroad times.

There's a whole couple threads on the job with some pics. The T-1138 does have a .73 OD so the NHC250 is going to be at its limit for power but if you keep the truck light it will run all day. Its low is not 2:1, but 1.72:1, so don't expect extremely powerful low range as in the original.

A nice thing discovered is that 4th becomes just like 5th was, so it is nice to drive at 40-50 when you want to. The 3-4 hole is a pest but not prohibitive on flat ground. It's not a race car so none of this bothers me. I was pleased to pass a couple of garbage scows on the highway. Never happened before.

In my avatar showing gauges, the readings are for 60MPH. The speedo needs corrected because it is falsely reading about 67.

Discusion topic: http://www.steelsoldiers.com/5-ton-...se-via-gearing-transmission-differential.html
and
Pics and discussion of the work: http://www.steelsoldiers.com/5-ton-...r-case-upgrade-t-138-t-1138-a.html#post696753
and
The axle swap thread: http://www.steelsoldiers.com/5-ton-up/38278-m39-series-5-ton-transmision-swaps-axle-info.html

Hope this helps. Please use the existing Discussion topic to get into any details, it's already there, includes talk about tires, engine swaps, brownie boxes, differential gears, and a few charts, and we should maintain it as a repository for the subject.