Allison 6sp: tranny problem...... maybe?

[mpeters0991]

So I put a different tune on my truck and I believe the Allison had enough time to learn it, and while I was driving between 55-65mph if I put my foot into it (not hard enough to make it down shift) it would go from about 1700 rpms and kind of just jump up to around 2100 rpm. It did it in 5th and 6th gear. So I pulled over and threw a different tune on it that I think was a little less potent, and I couldn't get it to do it. Any suggestions guys?

I'm not sure if its the tune, clutch packs, or converter, or whatever else it may be. Thanks again guys. If I was unclear about anything just say so and I will try to elaborate better.

Also, there were no codes present.


Thanks
Michael

 

[THEFERMANATOR]

Sure sounds like a converter letting go to me.

 

[mpeters0991]

Shouldn't it throw a code? Is there a way to figure it out with my v2?

 

[JoshH]

If you have a V2, you can datalog input, turbine, and output as well as selected gear to determine what is going on. I've seen a couple of trucks that would slip the clutch packs without going into limp mode immediately (both 6 speeds), but given enough time slipping, they will eventually limp and throw a gear ratio incorrect code. Most converter slipping I've seen is accompanied by a very pronounced shudder and noise, but the slipping clutch packs are silent and almost feel like the converter unlocked. However, the scan tool showed no converter slip speed, but the turbine speed would go up without a downshift or a corresponding increase in output speed.

 

[mpeters0991]

Alright I'll try to get it logged here in the next couple days, do you know what the spec range should be for those parameters? If I remember right there may have been a slight sound and shudder but I'm not real sure because it kind of just caught me off guard. Am I ok to drive around on it like this?

 

[mpeters0991]

When the converter is locked at 65.5% tccslip is 0-12 on this lesser horsepower tune I put on. Which that's not bad right? It's only up around 12 when your get into it

 

[x MadMAX DIESEL]

thats good, no slippage. my tc never once coded when it was totally f-ed

 

[AubleAK]

If you have a V2, you can datalog input, turbine, and output as well as selected gear to determine what is going on. I've seen a couple of trucks that would slip the clutch packs without going into limp mode immediately (both 6 speeds), but given enough time slipping, they will eventually limp and throw a gear ratio incorrect code. Most converter slipping I've seen is accompanied by a very pronounced shudder and noise, but the slipping clutch packs are silent and almost feel like the converter unlocked. However, the scan tool showed no converter slip speed, but the turbine speed would go up without a downshift or a corresponding increase in output speed.

Josh, what kind of noises will the converter make if its slipping?

 

[mpeters0991]

thats good, no slippage. my tc never once coded when it was totally f-ed

Alright thanks. Now when it was unlocked the slip would go from 0-550 at times. Does that mean anything? Also why does the tccdc only show it going to 65.5%?

Also what is the most slippage you want to see before you should start worrying?

 

[THEFERMANATOR]

I believe it has to be slipping for something like 10 seconds on a 6 speed for it to code for the converter clutch. I know the LMM I just tuned wouldn't hard code, but would throw a soft code for TCC slippage. It didn't shudder or anything, but even on a stock tune it would slip more than 300 RPM's while in lockup at 1/2 throttle. There is a PID in there for TCC slippage which takes the turbine and input and shows the difference.

 

[JoshH]

Josh, what kind of noises will the converter make if its slipping?

All the trucks I've seen that have had the converter slipping would sound and feel like you're running over the rumble strips on the side of the highway. I never saw one throw a code though.

 

[Mike L.]

TCC at 65% is not locked.

 

[THEFERMANATOR]

TCC at 65% is not locked.

If he's reading it with EFILIVE, I believe it stops at 65% for locked. When you open a OS for a 6 speed, it shows teh max duty cycle for a 6 speed at 65.62%, so that is as high as EFILIVE will display it locked at. Caught me off guard first time I seen it as well. A TECH 2 will display it as 100% I believe.

 

[Mike L.]

Tech 2 will display 96 or 97 max.

 

[duratothemax]

Tech 2 will display 96 or 97 max.

Mike thats only for the 5-speed TCC solenoids though.

The 06+ TCC variable bleed solenoids are "pressure proportionate to current" solenoids, which become fully saturated (ie, full open) at much less duty cycle. 65% duty cycle is considered "fully locked" on a PPC/VBS solenoid.

Ben

 

[x MadMAX DIESEL]

x2 97 will show for 5speed. and 65.62 will show for 6speeds.

 

[duramaxJoe08]

my lmm never through a code but you could feel the shudder for sure truck would hold 2500 rpm and not gain much speed after i built the trans the truck is compleatly different.

 

[x MadMAX DIESEL]

even when my tcc drug at idle where i needed to throw it in neutral it wouldnt code. maybe the 5 speeds will actually code better?

 

[THEFERMANATOR]

After the clutches are pretty well gone, I believe they no longer shudder. The LMM I tuned would just flat out shoot from 2000 RPM's up to 3500 when you rolled into it. No shudder or anything. It is definately torque converter slippage as it was easy to see on a datalog when monitoring TCC slippage.

 

[duratothemax]

maybe the 5 speeds will actually code better?

Yes, the TCC diagnostics on the 6-speed TCM software are a little bit more lenient (looser parameters) than the TCC diagnostics on the 5-speed TCM's from what Ive found.

I dont know why.