Gear ratio question

[Houston Ben]

Can having too high a gear get you bad mpg's? Also, was trying to determine my gear ratio by turning the wheel and counting the drive shaft revolutions. I have 28" tires and 1 rotation of the tire nets me approx 1 & 3/4 turn on the drive shaft, any guesses?? I've tried to look it up but can't find anything.....

[ls1nova71]

Yes, too high of a gear ratio can hurt your MPG.

When figuring your ratio, you need to turn the wheel 2 revolutions if its not a posi. Sounds like you have a 3.07 if you got almost but not quite 1 3/4 revolutions of the drive shaft

[BR3W CITY]

Too high of a gear itself doesn't hurt mpg, but the final ratio between the transmission gearing and the rear end gearing can. In other words, you can run a very high rear gear, if you have a very tall tranny gearing and/or "more" speeds (3spd auto vs 6spd manual for example).

It all boils down to what kind of rpm's you are turning at any given speed, and making sure the engine is working too hard at any point. Too low gearing and you'll dog on the streets but get better mileage and speed ONCE up-to-speed. Too high, and you can take off hard from a dig, probably smoking the tires, but you'll end up spinning the motor crazy trying to maintain 65mph.

Might as well pull the diff cover off and just count the teeth. Its nice to verify for sure what you have in there, as well as checking on the mechanical shape of the parts. Besides, its good maintenance to change the oil once and a while.

[mrhurt73]

going to high can hurt, but mine is 3.08 gear ratio with 215/75/15 tire size which makes it a 27.697 in tall tire.

and i get 22mpg, i keep speed in 70mph range, depending upon state i'm in.

but i also changed ratios in HP tuners so transmission would not always be shifting from overdrive back to drive too.

[Houston Ben]

Thanks for the replies all! The initial takeoff is fine, it just seems when I am on the freeway at speed it feels a little dog-ish if I give it just a little gas to speed up a little or while going up an overpass. the first tank I figured I was getting 19-20mpg but the second tank seemsto be getting less....

but i also changed ratios in HP tuners so transmission would not always be shifting from overdrive back to drive too

mrhurt73, that is probably what I need to do. Thanks for the help all!

[BR3W CITY]

If its doggy on the freeway then checking those settings out is a must. Sounds like either;

your tire size/gearing isnt set correctly and it thinks your at a different speed than you actually are,

OR your shift points are set poorly or just left at stock (let the shifts have a little bit of harshness to them, if they are too soft its really hard to tell if your slipping),

OR your lockup settings aren't correct (or the lockup wiring/brake switch isn't working or set right).

[Houston Ben]

Thanks for the help BR3W CITY!
I think it's all the above but the lockup. I am 100% certain that the tire size and gearing isn't set correctly and that the shift points are stock.

As far as the lockup, I think I have it set up right. When I hit the brake, the brake wire provides power going to my relay switch. Also, when I press on the brake peddle I can hear the relay activate.

Damn, I didn't know there was so much involved in this!! Oh well, still fun!

[BR3W CITY]

Originally Posted by Houston Ben

Thanks for the help BR3W CITY!
I think it's all the above but the lockup. I am 100% certain that the tire size and gearing isn't set correctly and that the shift points are stock.

As far as the lockup, I think I have it set up right. When I hit the brake, the brake wire provides power going to my relay switch. Also, when I press on the brake peddle I can hear the relay activate.

Damn, I didn't know there was so much involved in this!! Oh well, still fun!

Ben there are also settings for the lockup in the tune as well. You can set the speeds at which it can engage, and iirc you can also make another adjustment to the TCC adapt and Regulator offset.

[jorgensensc]

Ben,
You have the 6l80e right? Don't get wrapped up in the relay confusion. Just make sure the TCC wire to the ECM is getting 12 volts WITHOUT your foot on the brake (if you are using an 2008-10 trans, the wire going to the trans for the TCC needs power also, partway through 2010+ only the ECM needs the power from the brakeswitch). When you put your foot on the brake you lose the 12 volts. Make sure you are wired that way. The 4l80 is wired opposite, which is the way I wired my 6l80 initially. Hart_rod gave the correct wiring schematic. When I corrected mine I immediately noticed a difference. My understanding is the ECM controls TCC lockup under certain conditions, third gear and up light pedal acceleration being one of them. So if your TCC isn't engaging your clutch is slipping. As a side note I also noticed my trans temp went way down once I corrected the wiring issue. Hope this helps you a little.
Shawn

[Houston Ben]

Ahhh CRAP!!! I hope I didn't screw the thing up!!

Yes Jorgensen,my engine and transmission (6L80E) are form a 2011 1500... SOOOOOO Just so I'm clear.... I need constant 12v to the wire going to the computer..... the only time the wire will not be getting 12 volts is when I put my foot on the break.... is this correct??

[Houston Ben]

I have a problem then... I just went to my truck and I can not find a constant 12 volts that is cut off when I press the brake peddle... any suggestions??

[Houston Ben]

Or maybe I can run my relay different??

[Houston Ben]

Hi Shawn, I just re-read the lockup threat that hart Rod started and can only find where he stated the wire needs power when the brake is pressed, did something else come of this?

[jorgensensc]

Ben, I'm sorry brother! It's late here and I wasn't thinking clearly. You are correct. It needs power when brake is applied. Although I read this also http://m.ls1tech.com/forums/showthre...891&styleid=25
And it states that the wire to the ECM needs a ground when the brakes are not applied. So not only do we need 12 volts when brakes are applied, we need an actual ground when brakes are not applied. At least that is what I understand from the thread I read.
How do you interpet it?

[Houston Ben]

Hahahah, Shawn, you had me scratching my head all night! LOL. I will have to check that link out today and see what I can make of it.....but I am really just a beginner on this stuff.

BR3W CITY, Thanks for the info, I will have that checked out when I get it tuned.

[Hart_Rod]

Originally Posted by jorgensensc

Ben, I'm sorry brother! It's late here and I wasn't thinking clearly. You are correct. It needs power when brake is applied. Although I read this also http://m.ls1tech.com/forums/showthre...891&styleid=25
And it states that the wire to the ECM needs a ground when the brakes are not applied. So not only do we need 12 volts when brakes are applied, we need an actual ground when brakes are not applied. At least that is what I understand from the thread I read.
How do you interpet it?

Originally Posted by Houston Ben

Hahahah, Shawn, you had me scratching my head all night! LOL. I will have to check that link out today and see what I can make of it.....but I am really just a beginner on this stuff.

BR3W CITY, Thanks for the info, I will have that checked out when I get it tuned.

I think I get it now. Take a look at this diagram, this is how I'm going to wire mine. Ben you just need to add a resistor to your setup.

[jorgensensc]

Originally Posted by Hart_Rod

I think I get it now. Take a look at this diagram, this is how I'm going to wire mine. Ben you just need to add a resistor to your setup.

That is how I was thinking to wire it. But wait one minute. That was on an '08 6l80, not the 2010+ The previous ones wires the TCC straight from the brake switch, the newer ones wire through the ECM, which then sends the signal to the TCC. Do we still need to pull it down to ground if we are going through the ECM? I'll post up the wiring diagram differences.

[jorgensensc]

2008 6l80e

[jorgensensc]

2011 6l80e

[jorgensensc]

And the other 2011 6l80e

[jorgensensc]

Ok, so dumb question. In the 2011 schematic it shows the TCC valve having ignition source from the Tcm, which is running all the other shift solonoids also. Then the valve is triggered with the normally open ground. Which I assume is triggered by the ECM via canbus when it wants the TCC engaged. So, why would we supply no voltage to the ECM during driving? If we supply voltage only during braking doesn't wouldn't that tell the ECM to engage the TCC only during braking? But then it wouldn't engage because the TCC engage is a function of other data ( speed, gear, acceleration) that the ECM interprets and decides to engage or not. I understand why it would be done that way on the 2008-2010 trans, since the Tcm gets a signal directly from the brake switch. But on 2010+ trans there is no signal from the brake switch to the Tcm, only to the ECM, which then sends the signal controlling the TCC to the Tcm via canbus.
Ideas?

[Houston Ben]

Wow, this is going way over my head now, lol. From reading the LS1 tech form link it sounds like Hart Rod's idea will work. I see he had posted there to get confermation as well.

One question, can I still drive my truck or will this hurt the trans??

Also, I sent an email to 1050tunes.com who did my harness and asked how they recommended I wire this but have yet to hear back, I will keep all informed.

[jorgensensc]

My understanding is that it won't hurt anything, but again I'm no expert. I'm also very confused. The problem I really have is determining what the ECM needs to send the engage/disengage the TCC. 12 v or ground. On the older 6l80 I can plainly see why it needed the 12 volts, because the brake lights gave the ground when the brake was not depressed. On the newer trans it already has the 12v at all times, and the ground is switched by the Tcm from direction given to it by the ECM. So the question becomes, what does the ECM want from the brake action?

[dayj1]

Originally Posted by jorgensensc

So the question becomes, what does the ECM want from the brake action?

In your case, the ECM wants 12V to ECM connector X1 (pin 9) when the brake is pressed.

The easiest way to hook everything up is to connect the light blue/white wire going to pin 9 of ECM connector X1 to the same terminal of your stock brake switch that goes to the brake lights (it's usually a white wire in a GM harness and actually goes to the turn signal switch before heading out to the brake lights).

That way you don't need an extra relay at all. You also don't need a resistor in circuit at all unless you have LED tail lights as the filament in the bulb will work as a pull-down resistor to ground the light blue/white wire when the brake pedal is not pressed.

[jorgensensc]

Originally Posted by dayj1

In your case, the ECM wants 12V to ECM connector X1 (pin 9) when the brake is pressed.

The easiest way to hook everything up is to connect the light blue/white wire going to pin 9 of ECM connector X1 to the same terminal of your stock brake switch that goes to the brake lights (it's usually a white wire in a GM harness and actually goes to the turn signal switch before heading out to the brake lights).

That way you don't need an extra relay at all. You also don't need a resistor in circuit at all unless you have LED tail lights as the filament in the bulb will work as a pull-down resistor to ground the light blue/white wire when the brake pedal is not pressed.

This sounds great, but please help me to understand. Why would not having any voltage ( or possibly a ground through the lights) tell the ECM to tell the Tcm to flip the ground in the Tcm to engage the TCC solenoid?
Conversely why would giving the ECM 12 volts while braking tell the ECM to disengage the TCC?
Not trying to be difficult. I totally understand why it worked that way on the older 6l80, but the newer ones communicate differently with the Tcm.
Are most of the signals the ECM receives grounds or voltage? Why does the ECM need both voltage and a ground to send a signal to the Tcm via canbus?it seems like you would just need one or the other.
Can anyone elaborate any more?
Shawn