6WG-260 transmission , Terex TA-30

[Yazid Asaad]

Hi all

I faced a problem with a 6WG-260 Generation 1 transmission newly overhauled and I really need a help.
We replace K2, Kr, K3, and K4, we checked K1, Kv and everything looks okay.

We also replace the torque coverter with a used one because of the overheated marks on the old one.


After starting the machine up and test it, we found the the Automatic shifting is not working all the time. Sometimes it will shift up to the sixth gear but will not down gears or reduce it 5th to 4th gear for example, so you should to change it manually to reduce gears.

Sometimes it will shift from 2nd to 3rd and stuck up at the 3rd gear, even if you try to shift upward or downward, it will not shift on both Automatic and Manual. It will stuck up at the 3rd gear. The same also exactly happend at the 4th gear and few of times at the 2nd gear. During this the 3C or 39 or 3E codes shown on the display(just one code will show at time), when you totally stop the machine movement, the codes will disappear.

When this problem happend, we noticed that if you move the selector N to F, it will show 6F not 2F as usual.

Over one test , we drive it at uphill road ,then it start to reduce gears, 5th to 4th then to 3rd gear until the flat road then it stuck up at the third gear.

The display screen start to show NN when shift from forward to reverse gear, it will not select forward or reverse gear, just will blink NN when this problem happend.


We changed the gear selector, TCU(from another truck), output sensor, and turbine & internal sensor. We also found that the kickdown switch wires not connected so we connected it. We checked transmission harness and it seems okay.


Could the torque converter be the reason?or the TCU, I can send a video, I hope it clear enough.

Many Thanks

 

[Bigbert]

Never mind, Yazid.
We will sort it out.

 

[Vetech63]

Did you run the AEB calibration? Usually on the Terex you can use the AEB switch at the wiring plug in near the TCU (it depends on whether your TCU has that capability). Some models the AEB calibration is done through the monitor, or by a laptop.

 

[Yazid Asaad]

Did you run the AEB calibration? Usually on the Terex you can use the AEB switch at the wiring plug in near the TCU (it depends on whether your TCU has that capability). Some models the AEB calibration is done through the monitor, or by a laptop.

Did you run the AEB calibration? Usually on the Terex you can use the AEB switch at the wiring plug in near the TCU (it depends on whether your TCU has that capability). Some models the AEB calibration is done through the monitor, or by a laptop.

Yes . I run the AEB and the display shown okay, all the clutch es groub been calibrated.

The problem now in the upshift not working all the time , especially on the downhill roads. Also the down shift not work probably on both automatic and manual.
What should I check now?

 

[Yazid Asaad]

Never mind, Yazid.
We will sort it out.

For sure boss .

 

[Vetech63]

Any fault codes displayed?

 

[Yazid Asaad]

Any fault codes displayed?

When the problem start , the codes 3C ,3E or 39 shown up in the display for a short time.

 

[Vetech63]

3C
Logical error at output speed input. Check electrical cable from TCU to sensor
3E
Output speed zero doesnt fit to other speed signals. Check electrical cable from TCU to sensor, sensor gap, sensor signal
39
Logical error at internal speed input. Check electrical cable from TCU to sensor, sensor gap, and sensor operation.

All of the codes above put your TCU into substitute clutch control or limp mode.
It looks like the problem is more than likely electrical in nature. I have no experience on the TA 30's but do on the TA35's. On the 35's, Terex ran the wiring harness on the right side of the transmission up high, then down the back right side, right next to the exhaust piping. I had several trucks that the exhaust pipe was rotting out and hot exhaust gases were directed right at the wire harness, which in turn burned that part of the harness up badly. The thing is you cannot see that part of the harness unless you actually remove the harness from its loop mounts and pull it back through the floor panel inside the cab. Its a pain in the ass but its what has to be done. I suggest you do this and inspect all the wiring by removing the wire from that black plastic protection loom.

 

[Yazid Asaad]

3C
Logical error at output speed input. Check electrical cable from TCU to sensor
3E
Output speed zero doesnt fit to other speed signals. Check electrical cable from TCU to sensor, sensor gap, sensor signal
39
Logical error at internal speed input. Check electrical cable from TCU to sensor, sensor gap, and sensor operation.

All of the codes above put your TCU into substitute clutch control or limp mode.
It looks like the problem is more than likely electrical in nature. I have no experience on the TA 30's but do on the TA35's. On the 35's, Terex ran the wiring harness on the right side of the transmission up high, then down the back right side, right next to the exhaust piping. I had several trucks that the exhaust pipe was rotting out and hot exhaust gases were directed right at the wire harness, which in turn burned that part of the harness up badly. The thing is you cannot see that part of the harness unless you actually remove the harness from its loop mounts and pull it back through the floor panel inside the cab. Its a pain in the ass but its what has to be done. I suggest you do this and inspect all the wiring by removing the wire from that black plastic protection loom.

Thank you for the explanation. I already checked the harness by multimeter, everything looks okay. Then I connected output sensor by external wire to the cabin. And I do it for all sensors just in case. So we can exclude the harness for now.

I noticed something that I should share it with you. I fit a multimeter on the the output speed sensor pins in the cabin to check the Hz reading. The reading vary between 0.2 k Hz to 2.5 Hz. When the shifting problem happen, the Hz reading is fixed at one. I mean the reading will be fixed at 1K Hz, the sensor reading is not right. I changed the sensor with used one from another truck. The same readings.

So I think the problem is with the auto speed sensor reading or let's say it's in maybe it's inside the transmission.
I would say maybe the k3-4 group moving a little bit, so the sensor reading it's not fixed or not right all the time.


May the k3 big gear move close to the sensor and far away from the sensor, could that happened?

I also noticed when we rebuild it is that the bearing number 37 in the attached picture move freely on the k3 shaft so I used bearing lock tide and tight the nut 39 very will to fix it more.

What could make the output speed give wrong reading?

Thank you

 

[Vetech63]

Before we go any further, who rebuilt the transmission? Was it a reputable ZF rebuilder? The reason I ask is that the ZF transmissions are very specific on bearing preloads and rolling torques. Gears, shafts, drums all have a wear spec limit that they HAVE to meet to be reusable. I have a ZF rebuilder that has told me they have had transmissions fail on the dyno for excessive/ borderline wear limits.

I already checked the harness by multimeter, everything looks okay

If you are checking the wiring using continuity then you are only getting a connection. It doesn't necessarily mean the wire will carry the voltage needed. Even slight corrosion will make a difference.

I noticed something that I should share it with you. I fit a multimeter on the the output speed sensor pins in the cabin to check the Hz reading. The reading vary between 0.2 k Hz to 2.5 Hz. When the shifting problem happen, the Hz reading is fixed at one. I mean the reading will be fixed at 1K Hz, the sensor reading is not right.

I cant help you with this as I do not have parameters to check the sensors.

I changed the sensor with used one from another truck.

I know this seems to be a logical way to do troubleshooting but, it can also be a way to transfer issues from one truck/TCU to another. Every time you change a component the AEB will need to be rerun as the TCU has to calibrate it.

May the k3 big gear move close to the sensor and far away from the sensor, could that happened?

If the specified preload was too loose, yes.

I also noticed when we rebuild it is that the bearing number 37 in the attached picture move freely on the k3 shaft so I used bearing lock tide and tight the nut 39 very will to fix it more.

I'm positive that didn't meet spec. Im not sure if that specifically would cause your problem.

Here is some advice going forward from here:
1. If you are going to switch components from another truck to troubleshoot, you HAVE to run calibration with the AEB every time a component is changed.
2. Mark the original components somehow and make sure, if they don't correct the problem after an AEB run, reinstall the original component back in its place.
3. If your AEB run is finishing the calibration correctly, the display should notify you that the cycle is complete. I would deduct that if the problem is showing up while the truck is moving under power, with the codes still coming up that you posted above, something inside the transmission is loading/ shifting out of place and causing the problem.

 

[NPOMPELL]

I'M HAVING A SIMILAR ISSUE BUT WITH CODE B7 FOR OVER TEMP. DOES ANYONE HAVE A LINK TO OR KNOW WHERE TO GET A SERVICE/REPAIR MANUAL FOR THE ZF 6WG-260 ? THANKS

 

[Bigbert]

Hi NPOMBELL,

I'll share manual in a pm.
B7 is overtemp sump, you are right. Guess, higher than 95 degrees Celcius. When does it occur? After longhaul ride at high speed?
Check oil level, set level rather lower than hot max. at dipstick. If pump creates some noise at cold start AND high rpm it doesn't matter.
Check cleanliness of radiator, fan is working?

 

[NPOMPELL]

I WILL CHECK THESE THINGS AND AWAIT THE MANUAL. I APPRECIATE YOUR HELP!