M1078 LBCD and transmission shifting problems

[vanjosh]

Hey there, I'm working on an 1995 M1078 truck with an Allison MD3070 transmission and having some trouble. First off the LBCD (polarity distribution box) has a smallish wire with ring terminal im trying to figure out which polarity to connect it to. I didn't make a mark of whether it was from the 12 V load or 24 load side. Does anyone have a diagram of what is connected to the LBCD unit by default? They way I have it now is:
Stud 1: 12 V battery on the first stud
Stud 2: 12 volt alternator/12 V distribution to PDP (fuses,relays, etc)
Stud 3: 24 V alternator wire/24 volt distribution to PDP
Stud 4: 24 V battery

then loos wire im unsure of. Can anyone give any guidance?



Next problem, when I reconnected everything the truck fires up but it gives error codes that give it the no shift issue. The codes are the following:
D1 45 22
D1 44 22
D1 44 14
D1 22 16
D1 44 13


All of these are codes for transmission solenoids, and the 22 16 code is an output shaft reliability test. Does the transmission have anything to do with the LBCD connections? I am able to read and clear the codes but they keep coming back. Is there anything I'm missing?

 

[NDT]

Vanjosh welcome.
posts like yours need to go in the FMTV forum so that hive will see it.
Double checking, your truck is a 1995? It has a transmission controller with green digits?
Did this truck ever operate prior to you working on the electrical system?
It is highly unlikely all solenoids are bad. I would check the harness end to end for chafing or cut wires.

 

[vanjosh]

Yeah it ran before we removed the tire launcher and air/hydraulics system. It still runs just the minor problems with the shifting. I'm including pics of the tags inside the cab. Yes the digits are green. I checked all the harnesses I could easily get to for chafing/cut wires/shorts and didn't find anything

 

[MatthewWBailey]

Hey there, I'm working on an 1995 M1078 truck with an Allison MD3070 transmission and having some trouble. First off the LBCD (polarity distribution box) has a smallish wire with ring terminal im trying to figure out which polarity to connect it to. I didn't make a mark of whether it was from the 12 V load or 24 load side. Does anyone have a diagram of what is connected to the LBCD unit by default? They way I have it now is:
Stud 1: 12 V battery on the first stud
Stud 2: 12 volt alternator/12 V distribution to PDP (fuses,relays, etc)
Stud 3: 24 V alternator wire/24 volt distribution to PDP
Stud 4: 24 V battery

then loos wire im unsure of. Can anyone give any guidance?



Next problem, when I reconnected everything the truck fires up but it gives error codes that give it the no shift issue. The codes are the following:
D1 45 22
D1 44 22
D1 44 14
D1 22 16
D1 44 13


All of these are codes for transmission solenoids, and the 22 16 code is an output shaft reliability test. Does the transmission have anything to do with the LBCD connections? I am able to read and clear the codes but they keep coming back. Is there anything I'm missing?

I'd check the wiring diagrams posted in the TM section here. I use those all the time and they're accurate. Your loose wire should have a wire number on it somewhere. TL100 or TL1507 per this diagram attached.

I deleted my LBCD entirely

 

[hike]

I think the AO trucks have the Polarity Protection Device (OP shows), though not an LBCD. Not sure that is an A0 schematic @Ronmar would know—

 

[NDT]

Looking at the codes, such as solenoid short to ground and solenoid open circuit, it is clear to me that when your people were cutting off all the parts you mentioned, they f-d the transmission harness.

 

[vanjosh]

Looking at the codes, such as solenoid short to ground and solenoid open circuit, it is clear to me that when your people were cutting off all the parts you mentioned, they f-d the transmission harness.

The only things we disconnected electrically were the 2/0 AWG wires from the battery box to the polarity box, and the alternator wires/PDP wires, relocated the ground shunt, and deleted the ether start and driver alert button. We didn't touch any of the transmission harnesses or other harnesses. When we clear the codes we can get it to drive until a code gets tripped again so it doesn't seem like the solenoids are actually having problems but that maybe it's a computer issue. Would the transmission ECU be the first thing to suspect?

 

[NDT]

Looks like someone painted the dash puke yellow. Did you pull the dash off to do this? Maybe the connector did not get properly reseated in the WTEC controller.

 

[vanjosh]

No, we didn't touch anything in the cab, we did the bare minimum to delete the tire launcher and air/hydraulics by relocating the air cleaner, shunt, and polarity box. Here's a before and after pic

 

[NDT]

Someone took the dash apart b/c it’s not green anymore and all the screws are new. It’s real easy to improperly insert the harness connector into the WTEC. Suggest you check that.

 

[Ronmar]

Ok, just because you didn’t touch anything in the cab, doesn’t mean something isn't wrong…

first, a 95 will be an A0 truck it does not have a LBCD, it has a Polarity Protection Device or PPD(diodes in a heat-sync). Your alternator cables are on the wrong terminals. The batt and alt terminals go on their respective voltage battery terminals. The only thing on the load terminals are the cables to the power panel in the dash. As you described the connections, the batts will not charge as the alt output is on the wrong side of a check valve/diode…

As for the little wire, it should have a metal band label. What does that band read. At any rate, you don’t need to worry about it as it is probably just a STE(Standardized Test Equip) wire and is not used by the truck for operation you only need the 6 large cables connected tot he 4 polarity studs correctly… download the A0 manuals on the main page of this site, present conflict vehicles M1078. There is a schematic near the back of each manual. Gotta head to work or I would send you a link it will ID all the wire ends…

In 95 you would have had a WTEC-2 trans controller, incorporated with the keypad in the left dash. That module has 2 connectors on the back. One goes to the Vehicle Interface Module(VIM) under passenger dash and the other goes to a bulkhead connecter thru the engine tunnel in the front to the left of the radiator(up behind the grill). That is the main trans connector Harness that goes aft to the control/valve module on the trans and also splits to various sensors and transfer case controlls.

multiple short codes speakes to me of damaged harness. Old wire, probably chemical washed and deteriorated by chem war cleanup drills and even possibly sun deteriorated can be fragile. I suspect you have damage somewhere along that path.

the controller uses a 7KHZ PWM signal to check circuits for open and short based on the feedback it receives from the solenoids, and uses the same signal to ultimately energize solenoids on those circuits. Code 22-16 means that the output RPM/speed sensor is reporting data out of sync with the input RPM and turbine RPM Sensors.

his pretty much confirms a short in wiring, as that 7KZ signal is being applied to the output speed sensor circuit . If you look closely, you may even see the speedometer needle move… not supposed to happen. I have a similar issue, and throw that code when I select mode. I believe it is a short in the transfer case bulkhead connector on my truck…

i would start by hand over hand following that wire bundle from TCU to all the trans connections looking for obvious damage. Then I would start wringing out the harness with an ohm meter looking for the shorts that the TCU is storing as faults…

 

[MatthewWBailey]

The mastery is displayed yet again!!