Help: Allison MD3060 Firetruck

[ChevyMax56]

We got a firetruck in the shop today that is not locking up the TC when it gets above 250 degrees.

the tech that is working on has pressure gauges hooked up and says all pressures are good. He went and drove it and it shifted good he pulled over to turn around and stalled it out to bring temps up above 250 and took off again and it didn't lock up and hasn't locked back up since and temp is back down around 150-170.
The F solenoid is not activating. He didn't pay attention to that when it was locking up earlier.

You guys have any ideas? Thanks for your time

 

[duratothemax]

Uh...the trans should not be running anywhere near 250*...

And FYI, the converter is supposed to stay unlocked when the trans goes into "hot protection mode", above ~250*. Thats a normal strategy programmed into the TCM.

Im not sure what idiot tech there thinks the trans is supposed to be running over 250*, but get him away from the truck ASAP.

Ben

 

[Yellow Jacket]

With converter locked, cooler flow is reduced I believe... Therefore in hot mode the TCM unlocks the converter.

But Ben, should it automatically start locking again after cooling off? Or does it need to be shut down to reset? Only ever had one customer get one that hot, and Trans was smoked and cooler was plugged with clutch material and metal shavings...

 

[duratothemax]

With converter locked, cooler flow is reduced I believe... Therefore in hot mode the TCM unlocks the converter.

Yep! Its kinda counter-intuitive...you'd think "hot mode should keep the converter locked...less slipping, less heat"....BUT I guess Allison has done all the math and figured out that an unlocked converter (theoretically generating more heat) flowing more to the trans cooler is worth more for trying to save the trans than locking the converter (generating less heat) and lowering cooler flow....

But Ben, should it automatically start locking again after cooling off? Or does it need to be shut down to reset? Only ever had one customer get one that hot, and Trans was smoked and cooler was plugged with clutch material and metal shavings...

Maybe, not sure. Depends how the TCM is programmed. Maybe Allison has the medium duty/severe-abuse transmissions programmed to stay in hot protection mode for the remainder of the ignition cycle, regardless of if the trans cools down??

 

[ChevyMax56]

I appreciate the help guys. I don't work on trucks I work more on heavy equipment.

 

[PureHybrid]

I want to know who decides brake stalling it to 250°F was a good idea...

 

[THEFERMANATOR]

Do you know if it has a retarder on it? If so 250 is not that hot as 280-300 is normal when the retarder is active. Not sure on others, but I know mine locks the converter, shifts hard through the gears, and runs in a mode similiar to tow/haul when it goes into overheat mode.

 

[ChevyMax56]

he found that it doesn't go into heat protection tell the temp hits 262. there running synthetic oil in it. It shifts normal even at 250 just wont lock up tc. Even first thing this morning it still wont lock up. The F solenoid is not activating. does anyone know if this tells it to lock up? it does not have a retarder on it. Also its not logging any codes.

 

[JoshH]

F solenoid is the TCC solenoid on a 1000/2000 series. I'm not sure on a 3000, but it very well may be.

 

[andy-stevenson]

Has he tried replacing the F solenoid?

 

[ChevyMax56]

He has not tried it yet. But we've been talking and have narrowed it down to that but we just weren't for sure if that control it or not. on the status screen the tcm isn't telling it to activate or deactivate the F solenoid.

 

[greendury]

Does it have any abs codes. The Allison will keep the converter off if there is an abs event. You can see this in the doc software. I see this issue alot.

 

[ChevyMax56]

It did have an abs code. cleared it and still wont lock up

 

[Frankin_truck]

What gen of Tcm does it have? the gen4 is larger and the gen 5 is size of a a40 Tcm. What I am getting at is I have had lots of bad gen 5 Tcm s in 3000 series Allison's

 

[Chevy1925]

i would drop the pan and open the filters up.

 

[ChevyMax56]

What gen of Tcm does it have? the gen4 is larger and the gen 5 is size of a a40 Tcm. What I am getting at is I have had lots of bad gen 5 Tcm s in 3000 series Allison's

its a 2001 ally, the software is 9A2 (if that matters)

i would drop the pan and open the filters up.

I've asked why he hasn't and he said he doesn't want to drop oil and filters just yet. but I agree its down to that point. We do all the time on heavy equipment.

 

[Chevy1925]

its a 2001 ally, the software is 9A2 (if that matters)



I've asked why he hasn't and he said he doesn't want to drop oil and filters just yet. but I agree its down to that point. We do all the time on heavy equipment.

id also check the pan for material in the bottom. his brake stalling is not helping the trans one bit and actually killing it. there is no air movement over the coolers when he does that other than what the fan is bringing in and at the 1500-2k rpm hes probably stalling it to, thats no where near enough air with that load.

 

[THEFERMANATOR]

There isn't an easily droppable pan on a 3060 series trans. The filters go into seperate slots in the trans near the bellhousing, it's been so long I don't remember if you lose all the fluid when you drop them or not. And once they're out, you can easily see the filter media. It should be of note the 3060 is virtually nothing like the 1000/2000 series. Sounds like something is blocking lockup at the TCM. Overheat shouldn't stop lockup as I have seen them up to 320 with the retarder on, and it stayed in lockup just fine. Have you tried commanding lockup while driving to verify if lockup will still work? Is this a mechanical or electronic injected engine? I know the mechanical engines had alot of trouble with TPS's going out of adjustment or going wacky.

 

[ChevyMax56]

There isn't an easily droppable pan on a 3060 series trans. The filters go into seperate slots in the trans near the bellhousing, it's been so long I don't remember if you lose all the fluid when you drop them or not. And once they're out, you can easily see the filter media. It should be of note the 3060 is virtually nothing like the 1000/2000 series. Sounds like something is blocking lockup at the TCM. Overheat shouldn't stop lockup as I have seen them up to 320 with the retarder on, and it stayed in lockup just fine. Have you tried commanding lockup while driving to verify if lockup will still work? Is this a mechanical or electronic injected engine? I know the mechanical engines had alot of trouble with TPS's going out of adjustment or going wacky.

How do you command lock up in DOC? We had the ecm sent and flashed to latest software yesterday and its still not locking up. the tech working on it is in msha class today so he wont be able to mess with it. He says the TPS is reading what he is commanding it to.

We don't normally work on Allisons so our manager is really uneasy on letting us have much reign on troubleshooting this. and the customer doesn't want it hauled or driven the 2 and half ours to the closes Allison dealer.

 

[ChevyMax56]

UPDATE: Today the tech test drove it and the torque locked up. the F solenoid is controlling lock up. He did the exact same thing as in first post. but the actual temp is only 205 not 250. the gauge in dash says 250 though. The tc locked up consistently. we told customer to come get it and drive it around today and see if it acts up again.

Thank you guys for your help much appreciated!!