M1078 4x4 non existent

[Btwedel]

Hi fellas, newbie here , I've got a 1997 m1078 that I got thru my local rangeland fire protection agency (rfpa) . I'm having trouble with the 4x4 on it . I've got no 4x4 , I turn the mode on and doesn't make a difference. If I put it in the mud it spins the rear wheels and also the front drive shaft does not turn ... we got these trucks from the military thru a grant and they have some of the goodies missing ... this truck does not have the ctis on it anymore ... it had relays mixed around so the alternator wouldn't charge. .. anyways enough expounding .. anyone have any info on the transfercase / 4x4 issue?

 

[porkysplace]

Welcome to SS . Since this post is in the CUCV forum you might not get much help The correct forum for these is
[h=2]FMTV[/h]
Post up your Family of Medium Tactical Vehicles Q&A here.

If you don't already have them you can download the Technical Manuals here.

[h=3]M1078 TM's[/h]

 

[waayfast]

Hello,
Welcome to the site from Salmon River Country! Congrats on the new ride and while I know NOTHING about the new fangled m1078's there are plenty of knowledgeable folks on here that will be able to help.

This site is a great resource with great folks, oh yeah ---we gotta have pics!

Jim

 

[Suprman]

Front shaft does not turn at all? In mode? The trans keypad can display error codes see if there is anything stored.

 

[NDT]

In Mode, the WTEC controller commands the transfer case interaxle differential to lock. This does not appear to be happening based on what you describe.

 

[Suprman]

There is a connector on the transfer case, part of the transmission wire harness, that controls lock and unlock on the center diff. When you are not in mode and the rear is slipping you may not see power to the front and this can be normal.

 

[Btwedel]

Ok.. if the connector is not making contact it could be just staying unlocked when the mode is on?

 

[Btwedel]

Also can you give me a rundown of how to check the codes?

 

[Suprman]

Arrow up and arrow down at the same time. There is an allison guide online that tells all. A visual inspection of the trans harness and connection couldnt hurt.

 

[Awesomeness]

Arrow up and arrow down at the same time. There is an allison guide online that tells all.

What guide is that? I tried doing some googling for stuff like "Allison WTEC II guide", but didn't seem to produce anything useful.

 

[Btwedel]

D1 - 13 13 is the only code I'm getting ... I cleared the code and it immediately resets when you drive.. haven't had time to slide under and check the harness and plugs .. as it is raining and muddy out...

 

[coachgeo]

There is actually a ton of youtube videos on Allison Selectors , getting codes, using them etc.

Here are a few Online Code PDF's that should closely resemble our models: say closely cause "suspect" not many books on the 3000/4000 model tranny will include some codes that pertain to our oddball T-Case addition.

. http://www.beamalarm.com/Documents/allison_transmission_codes_manual.html
. http://www.rvtechlibrary.com/transmissions/shift_selector.pdf

in both that code is listed as a wiring or voltage issue. Side note here.... Will/Suprman has mentioned that low voltage output due to Alternator issues can play havoc on tranny functions as well.

just for reference: Below manual was the most detailed covering far more than just keypad codes like the two above
https://www.google.com/url?sa=t&rct...wLe3inWogJRG6r41w&sig2=YNbjmXlL9XvHIkwAbbdHHA




UPDATE: Just found one that is said to list the MD3070 WTECH II (unfortunatley not the 3700sp that uses the WTECH III though but I bet much of the error codes are the same. ) it is very detailed like manual link just above
http://ww2.justanswer.com/uploads/H...ison_transmission_md3060_trouble-shooting.pdf

 

[Btwedel]

Thanks guys ,really helpful , I'll be digging in , in the near future I'll be sure to update ... thanks

 

[NDT]

Code 13 13 is ECU input voltage medium low. Is your alternator working correctly? The Allison can't stand working with just battery voltage.

Here is the useful WTEC II manual:

 

[Btwedel]

I believe so ... according to my volt meter in cab it about 27 volts +or -

 

[Suprman]

Ground the ecu housing. It's only grounded thru the dash plate.

 

[Btwedel]

Well put a ground from the housing to the cab and checked the connections on the Trans and transfercase also put a little bit of electric grease in em ... now, I have roughly 2.7 volts coming out the d pin and 2.6 out the c pin .. this is the little round plug on the transfercase ... anyone no what these should have in em ? Doesn't make any difference when you turn the mode on... ; (

 

[Suprman]

Could be a harness issue. Make sure the 2 plugs on the back of the ecu are in all the way they like to slip out. I think the tm has some troubleshooting for similar issues.

 

[NDT]

Well put a ground from the housing to the cab and checked the connections on the Trans and transfercase also put a little bit of electric grease in em ... now, I have roughly 2.7 volts coming out the d pin and 2.6 out the c pin .. this is the little round plug on the transfercase ... anyone no what these should have in em ? Doesn't make any difference when you turn the mode on... ; (

The solenoids are powered by "pulse width modulation" so you can't simply disconnect the harness and expect battery voltage to be there. The diagnostic manual I posted will help you, there is info there specifically for the FMTV. You will have to do some learning about this transmission in order to fix it.

 

[coachgeo]

The solenoids are powered by "pulse width modulation" so you can't simply disconnect the harness and expect battery voltage to be there. The diagnostic manual I posted will help you, there is info there specifically for the FMTV. You will have to do some learning about this transmission in order to fix it.

Just for reference. in earlier post #12 the update at the bottom of the post; the link placed there, is the same pdf NDT is referring too.