Removing TM on a 6L80E - helpful, hurtful or hard to say? (the answers are inside)

I would say this in another way, the topic is fun, but the actual discusion is really nothing but BLA, BLA, BLA.

I'd really like to read something more interesting about this trans, like the way it actually works. TM is not there to save the trans but to reduce the power at the time to shift, which translates to what then ?? turning TM off is the only way to go ?

If i had doubts before, now i'm 100% sure we can turn TM off because all the "facts" in this thread. :worship: :crazy:

We have no problems discussing about VE tables, fuel transients, MAF transfer tables, timing tables and how to optimize everything. then comes the trans, and well, we get a thread like this....really ?

With all respect, i think disabling TM 100% is a really good excuse for some people. Personal opinion.

Here's the tune I have been running for 4 years....

Sorry to bring up an old thread but was just reading over some TM stuff.

I was under the impression that TM function was to pull timing and reduce the torque output whilst the trans was shifting gear. This allows so longevity of clutches and a theoretically quicker shift if you want to lower shift times.

Removing TM as suggested would see much more torque being produced through the shift which makes it harder for the clutches to grab and harder to achieve lower shift times. The simple rule was that if you wanted super quick shifts that you left TM on. The shift would be able to be quicker as TM was pulling the timing and allowing the shift to take place. People thought the shift was taking longer but they were referring to the whole shifting process and feeling the timing being pulled and then ramped up again. but somewhere in the middle of that process the TM was actually allowing the physical shift to be achieved with less clutch wearing.

Never heard of TM controlling slipping?? Happy to be proven wrong though??

^^^ pretty sure you are right :)

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Originally Posted by bluessv

Removing TM as suggested would see much more torque being produced through the shift which makes it harder for the clutches to grab and harder to achieve lower shift times. The simple rule was that if you wanted super quick shifts that you left TM on. The shift would be able to be quicker as TM was pulling the timing and allowing the shift to take place. People thought the shift was taking longer but they were referring to the whole shifting process and feeling the timing being pulled and then ramped up again. but somewhere in the middle of that process the TM was actually allowing the physical shift to be achieved with less clutch wearing.

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Agree 100%

I read a lurk on here a lot but rarely post. I hope you guys are right. I just shortened my shift times by 50% and pulled all TCM commanded TM out of my '11 Silverado. I love the feel of the WOT shifts. I just hope it doesn't break anything.
:pray:

It's really not to noticeable when I'm easing around town but it's amazing to me that a stock trans can chirp the tires on a 1-2 shift and scratch the ground on a 2-3 shift in a 5700# truck.

Do you guys think I went too far?

I left work and drove it far enough to get a log of varying conditions. My LTFT's are running a little lower than I like. I can tell you that the 100mph speed limiter is gone. The transmission is still amazing me, it spins enough when it hits 2nd that it kicks the traction control on (if I don't have it turned off) and at 94mph it shifted into 4th and my head bounced off of the headrest.

Anyone think that I took it too far?

The engine TM is still limiting torque below 3000rpm. My gas PE table is commanding it to get way rich on the top end.

Think I should add some more 1st gear torque in it? Lean it out a bit on the top? I know that I can get a little more out of it on both the top and bottom.

This is a daily driver that I plan on keeping for years.

There is a lot of "FAIL" in this thread about TM. Removing it will allow for quicker, harder shifts. Leaving it on, will make grandma happy...

Mine is shifting hard enough that I'm a little worried about the drive shaft and U-joints holding up. I'm thinking about easing off on the shift times.

My opinion is whether on not you have a stock or built transmission. If you have a fully built tranny, go for and remove some or all the TM, but if you have a stock transmission, leave it on at least partially. The less torque the clutch plates have to deal with, the faster they can engage and the less abuse that have to deal with. Basically the shift pressure and shift times is the main play in a stock transmission. In a built tranny, things are a bit different :)

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Originally Posted by KY_BOB

Mine is shifting hard enough that I'm a little worried about the drive shaft and U-joints holding up. I'm thinking about easing off on the shift times.

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My Denali is AWD. I ripped out the rear driveshaft yoke.. Gm replaced under warranty. If your catch traction it CAN happen.

I have TM for just 1-2 upshift, othewise it breaks Nitto 555r's loose at the track, and I'm pretty much stock.

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Originally Posted by midevil1

My Denali is AWD. I ripped out the rear driveshaft yoke.. Gm replaced under warranty. If your catch traction it CAN happen.

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Out of curiosity, did you put the stock tune back in it before having the warranty work done? I'm just wondering if the normally check that kind of thing when you bring one in with a CAI and exhaust.

I know if mine does what yours did, it because of my tune. I'm still in awww over what that trans is capable in stock form but tuned. If I turn off StabiliTrak, mine actually tries to wheel hop going into 2nd at WOT. (of course, you don't have that issue with AWD and coil rear suspension). That makes my rear U-joint even more susceptible to breaking.

Education time...TM "DOES NOT" pull pressure, only timing. I will post some logs later monitoring actual clutch pressure. When a tranny is tuned correctly, a car with TM will actually shift harder than one with it turned off. Yes the car will ET slower because your removing power from the shift, but your shift will be faster and more violent. Again I caviot that with tuned correctly. I never turn TM off totally. Tuned with different TM throughout the RPM will feel better and last longer. This clutch to clutch tranny is crazy strong in gear, but weak during the shift. GM did not design TM for shift feel, my understanding is this was a bi-product of pulling power during initial Allison testing. They kept burning up the tranny during testing behind a high torque motor and had to figure out what to do in order to make a shift completion. I personally run no TM at WOT and that is also how I tune vehicles. But, I run full TM throughout allot of the RPM range (converter dependent). I know I am decreasing tranny longevity at WOT, but I prefer the shift feel and faster ET. It's all about the tune, and there are allot of ways to skin a cat with the 6L80E. I promise you with 100% certainty TM will extend the life of your tranny and NO it does not pull line pressure ONLY timing. Get the shift times and pressure tables matched correctly and youll have the hardest fastest shift you've ever felt with TM, but the car will be slower. I do put in a little TM at WOT for cars making over 600HP to the wheels. They tranny seems to like this and the clutches come back after inspection looking 10 times better than no TM.

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Originally Posted by bluegoat06

I would say this in another way, the topic is fun, but the actual discussion is really nothing but BLA, BLA, BLA.

I'd really like to read something more interesting about this trans, like the way it actually works. TM is not there to save the trans but to reduce the power at the time to shift, which translates to what then ?? turning TM off is the only way to go ?

If i had doubts before, now I'm 100% sure we can turn TM off because all the "facts" in this thread. :worship: :crazy:

We have no problems discussing about VE tables, fuel transients, MAF transfer tables, timing tables and how to optimize everything. then comes the trans, and well, we get a thread like this....really ?

With all respect, i think disabling TM 100% is a really good excuse for some people. Personal opinion.

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As for some 6L80E theory, the TCM monitors delivered torque output. It then tells the ECM based on shift parameters how much timing/pressure to pull/add. If your delivered torque signal is skewed (bad MAF/VE cal) your car will shift like crap. The TCM also uses delivered torque calculations for determining the rate of apply, just as the apply ramp does for the TCC. Unfortunately HP has not mapped these values so we can't manipulate this yet. You could however skew your MAF cal at upper RPM's to make the engine think it's putting out more torque than it actually is. I would say this would be best suited on a dyno to get the timing and AFR correct. There is some progress being made with valve body modifications in order to speed up the shift timing. We had the 3/4 shifting so hard (50ms) it actually snapped a shaft. That project is on hold while some 2/3 modifications are made. Those shifts are now at 50ms and feeling real nice.

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Originally Posted by Waker

As for some 6L80E theory, the TCM monitors delivered torque output. It then tells the ECM based on shift parameters how much timing/pressure to pull/add. If your delivered torque signal is skewed (bad MAF/VE cal) your car will shift like crap. The TCM also uses delivered torque calculations for determining the rate of apply, just as the apply ramp does for the TCC. Unfortunately HP has not mapped these values so we can't manipulate this yet. You could however skew your MAF cal at upper RPM's to make the engine think it's putting out more torque than it actually is. I would say this would be best suited on a dyno to get the timing and AFR correct. There is some progress being made with valve body modifications in order to speed up the shift timing. We had the 3/4 shifting so hard (50ms) it actually snapped a shaft. That project is on hold while some 2/3 modifications are made. Those shifts are now at 50ms and feeling real nice.

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Why are you making valve body mods to speed up shift timing if you say you can already make it shift as hard as you like and snap a shaft?

Splitting hairs but the TCM simply requests a torque number from the ECM and indicates a shift type like 2 > 3 plus a start marker and the ECM pulls timing accordingly for that shift.

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Originally Posted by LSX378

Why are you making valve body mods to speed up shift timing if you say you can already make it shift as hard as you like and snap a shaft?

Splitting hairs but the TCM simply requests a torque number from the ECM and indicates a shift type like 2 > 3 plus a start marker and the ECM pulls timing accordingly for that shift.

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The valve body mod accompanied with a real aggressive tune snapped the shaft. Tuning alone is not going to let these things hold extreme HP with any sort of longevity.

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Originally Posted by Waker

Tuning alone is not going to let these things hold extreme HP with any sort of longevity.

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As "thesubfloor" has proven :cool:.

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Originally Posted by LSX378

As "thesubfloor" has proven :cool:.

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I don't start to see shifting issue until around the 700-800 RWHP mark. It usually takes a little bit of TM to safely get the shift. I think with some valve body mods we could comfortably get the tranny to 1000HP and not worry about premature failure.

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Originally Posted by Waker

I don't start to see shifting issue until around the 700-800 RWHP mark. It usually take a little bit of TM to safely get the shift. I think with some valve body mods we could comfortably get the tranny to 1000HP and not worry about premature failure.

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Very :cool:. That will put the naysayers on the A6's out to pasture. :drivin:

When you say "little bit of TM" do you mean via shift torque factor?