Allison 6sp: TCC drag

[x MadMAX DIESEL]

Lastnight I noticed it was very easy to bark my turbo, shortly after that I found myself in limp mode stuck in 4th gear for about 10 mins before I got to a parking lot, I was gonna turn off the truck and try and clear the codes to get it out of limp because I couldnt clear them with the engine running. Thats when I noticed my trans temp gauge about 250*

I couldn't get the truck to come out of limp still, and it would go into reverse and drive very violently. So I just drove home about 15 miles in limp and figured the trans just needed to cool off for the night and I'd be back with my same old truck the next morning.

My thoughts were right and now I have all the gears again, but I think my TCC is dragging at idle. Driving to walmart today it was still very very easy to bark the turbo, so that points me to a TC not fully unlocking...

When I come to a stop I need to put my truck into neutral or it will push thru the brakes very hard, I logged it but for some reason the log file is not working so I cnat upload it. I noticed that with the truck in gear at idle the turbine speed goes to 0 and input speed is about equal to TC slip. Not sure if that means anything or not?

I also noticed that when at a light or stop sign, if I dont put the truck in neutral it will start blowing black smoke out of the exhaust? pretty scary sign lol


I was kinda more worried about getting my truck drivabl again lastnight than writing down the codes, But I do know that I got the p0741 code


Any help would be great. I kinda read around alittle and I think it could 3 things, TCC dragging, stuck valve or a bad pressure control soleniod?

 

[DAVe3283]

Log your main fuel rate. It does sound like a dragging/sticking TCC to me. If you come to a stop and the fuel rate goes way up, then that's your problem. It also explains the black smoke and wanting to push through the brakes, as well as the transmission heat.

 

[x MadMAX DIESEL]

thanks I'll try that tomorrow, I just don't understand how it would change, Its the same tune I've been running for awhile. RPMs look normal for idle speed, maybe alittle lower when in gear fwiw

 

[JoshH]

I doubt it is tune related. Like you said, either the converter clutch is dragging or there is something in the converter broken.

 

[x MadMAX DIESEL]

I might take it to the dealer, maybe they can do something with a tech II to figure it out? I don't want them tearing it apart unless they know forsure (I'm on a tight budget) The thing that I thought was odd is the smoke, I've never heard of anything like that before? I doesn't just haze it looks like I have the DieselPlace smokeswitch

 

[JoshH]

I'm sure it is putting a lot of fuel to it to keep the RPM up (fighting against the converter). Since your rail pressure is probably pretty low at that RPM range, I'm sure you are getting a lot of pulse width and probably really low (if not even negative) timing. All of which is a pretty good recipe for smoke. Get the converter freed up, and I'm sure your smoke issue will go away also.

As for your observations of turbine and input speed, that is exactly what you want to see when the truck is in gear and not moving. If you see turbine speed without the vehicle moving, it means you have clutches slipping. Turbine speed is how fast the transmission input shaft is turning. Unless you are moving, it shouldn't be turning.

 

[x MadMAX DIESEL]

Thanks Josh, that sounds like a good theory. A warming one, I was hoping I didn't damage a bunch of things at one time (though I probably did lol). Better get a loan out for a build.

 

[MACKIN]

If you can get your TC to drag with tuning that would be news to me and the fact that I know nuttin about tuning is news to you.

Easy enough to diagnose ,return it to stock calibration ,I would think to eliminate.

Last time I had a dragging TC ,C1 clutches were welded together in my transmission was full of debris causing valves to be stuck. So my money would be that you have foreign material ,clutch lining material, interfering with valvebody flow.

Drop the pan see whats in there.

 

[x MadMAX DIESEL]

I was thinking about that, I did find out my Main fuel rate goes up in the 70s when in drive. So thats the smoke deal. I was thinking a valve stuck too, I have beatin the living shit out of this trans. Would a trans flush would blow the debris out of it?

 

[LBZ]

I was thinking about that, I did find out my Main fuel rate goes up in the 70s when in drive. So thats the smoke deal. I was thinking a valve stuck too, I have beatin the living shit out of this trans. Would a trans flush would blow the debris out of it?

Save the trans flush money and put it into the rebuild that I think your gonna need. Sounds like your trans is shot.

 

[05dmaxdriver]

x2 time to build a trans !!

 

[x MadMAX DIESEL]

Feel free guys to donate to my charity.. Its for a build :rofl:
Just called them and it would be $250 for a flush and I'm not gonna do that if its not a garuntee fix. The truck does feel more powerful driving with a sticky converter though lol


Thanks for all the help

 

[x MadMAX DIESEL]

Limped it at half throttle, with P0777 code

 

[Kat]

Limped it at half throttle, with P0777 code

As Mike says that is the "Heart Attack" code.... Time to build it.

 

[MACKIN]

At 500 RWHP with a near stock Allison it's cooked. Unsticking the valvebody of debris wont matter much because your clutch linings are worn beyond holding.

 

[DAVe3283]

I was thinking about that, I did find out my Main fuel rate goes up in the 70s when in drive. So thats the smoke deal. I was thinking a valve stuck too, I have beatin the living shit out of this trans. Would a trans flush would blow the debris out of it?

Holy That'd do it!

A transmission flush probably wouldn't fix it. You could drop the pan and see what is there, put on a new internal filter and spin-on, which would probably help if it is just a plugged up inlet.

But I'm with everyone else, it's time to get the trans built. I'd donate to your charity, but I've got one of my own going for my trans :baby:

 

[x MadMAX DIESEL]

Yea I know, its pretty much settled in now. Gonna turn it down to my tow tune