6l80e Tow Haul problems

[Jonblarc7]

In my denali my trans shift fine without Tow Haul mode on. But as soon as you turn it on it goes all to hell and I'm so new to this I don't know where to start.


The problem

If I'm cruising down a flat road at 45 mph and turn on TH mode. With out changing throttle position or going up or down a hill. It immediately down shifts on gear to about 3,000 rpms then drops one more gear and now I'm sitting at 4,500 rpms just cruising down the road. And the down shifts are violent.

I pull a pretty big wakeboat and I can use TH mode at all. I have to manually shift it which it does fine, it's just annoying.

Here is the last tune I'm running, and I can log it to show you. I just wanted to ask if there is anything I need to set up in the log to look for first.

Blair 08 GMC Denali 2 ST fuel trim 4-27-17.hpt

[Rigo_eff1fitty]

Under pattern a d2 set it back to stock . I believe pattern a is for tow haul of not try patten b. But i believe its a

[Jonblarc7]

ok Thanks I will give that a try. I really would like to use TowHaul mode this weekend.


I was going to use the BlueCat tool to retune my trans. Do you know how well it works???

[Rigo_eff1fitty]

I have never used it but ive heard it works great.

[Jonblarc7]

So I tried pattern A and pattern B with no luck. As soon as you turn on Tow Haul mode. It starts dropping gears until it's running 4500 rpms. Then it won't up shift until your wide open. The truck pulled the boat an hour each way in manual mode fine.

Here is a short log of what it's doing. I pulled out and got up to about 45 and let the trans settle while I was on a flat road. I turned on Tow Haul mode and didn't increase the throttle or let off and up can see it start down shifting.


5-27-17 tow haul.hplBlair 08 GMC Denali bluecat 5-27-17 and pattern b back to stock.hpt

[Jonblarc7]

Also I add the bluecat info. The trans runs great I just need to adjust when it lock the TCC in 6th. It's just doesn't do it until 57-58 mph. I would like it to be just a-little sooner. Any suggestions


Thanks

[Rigo_eff1fitty]

Did you changed under d2?

[Rigo_eff1fitty]

try setting pattern a 5th 6th and d2 back to stock that got my issues fixed on a 2011 6l80 if not try pattern b.

[Jonblarc7]

Thanks man that got it. I put a stock tune from a 2010 Denali under pattern A. But I did all of them like you said.

If you got any suggestions on how to lower the lock up speed in 6th to about 50 or 52 I'm all ears. Right now it doesn't drop those last couple hundred RPMs until almost 60.

[Rigo_eff1fitty]

I am not to good with gm but i am guessing under apply release speed the 6th tab in normal . It all goes with throttle position %. So depending how heavy you got your foot on the pedal lower down the valeues their over 57 try lowering to 52 on the areas you want it to lock up early

[Rigo_eff1fitty]

I also suggest raising your wot shift rpm to 6200

[Jonblarc7]

Well pulled the boat to the lake today.

I made it 2 miles from the house then next thing I know. It starts dropping gears out of no wear and I'm sitting at 5000 RPMs before I could get Tow Haul off.

I guess I'll try and put everything under pattern B back to stock. And pull the boat again. If that doesn't work I guess I'll set the whole truck back to stock.

[Jonblarc7]

Well I set the whole trans tune back to stock to se if that would make a difference.

It didn't so I guess I'll take it to a trans shop or set it on fire.

I just don't get why the trans shifts fine in all other mode but Tow Haul.