Denali 6-speed - Needs Tweaking!

[Raymond Lowe]

Overall, I really like this transmission. Under light to moderate acceleration, the shifts are smooth and the truck really boogies. But getting on a freeway ramp takes a deft touch on the throttle. I give the throttle just a wee bump to get it to downshift and then ease into the throttle. It will gain speed very quickly and normally you're OK.

 

But, if you need to really punch it and you're already doing 30-40mph, this thing sucks! After a big pregnant pause, it's going to drop down at least 1 or 2 gears lower than it should, the RPM's are going to shoot up near redline, and the truck isn't going to accelerate much at all cause now it's in the wrong gear. And then you instinctively let off the throttle worrying about the screaming engine which makes the manuevre all that much uglier and now all your passengers are staring at you like you're a dork.

 

I'm training myself to slip into manual shift mode when I'm entering a short ramp but this shouldn't be. I agree with others that suggest this tranny needs a software update. I like the fact that it downshifts quickly with a little bump of the throttle when you need it to but these wild RPM downshifts when passing need to be fixed.

 

Anybody at GM listening?

[BigJayDogg3]

If I remember right a good tune takes care of that problem.

[MS3DALE]

If I remember right a good tune takes care of that problem.

Yep,Should.They've always helped mine.

[BigJayDogg3]

**Threadjack**

 

Hey Rich, the Corsica is a Chevy right? What was it in other lines. Like how the Sierra/Silverado are basically the same vehicle and the Trailblazer/Envoy are for all practical purposes the same vehicle, what else is the Corsica?

[MS3DALE]

Well,The 2-door version of the Corsica was the Chevrolet Beretta (Which my mom has a '96)

Now up in Canada the Chevrolet Corsica was know as the Pontiac Tempest...Cool huh?

[BigJayDogg3]

yeah it is. I have seen a few of them around here, but couldn't for the life of me remember what they were called in other brands. Thanks.

 

Now back to our regularly scheduled thread.

[2017HD]

My manual for a 2500HD says to use half throttle when accelerating between 40 and 60. I have found that when accelerating if I wait for the tranny to hit 3rd and then lean into the throttle and keep the revs up around 3000 I can go like a bat out of h%#L while continuing on to 6th. The other approach I have taken is to hold the revs to around 2000 and take my time reaching 60 - which BTW is 2000 in 6th.

[Bostonsfavson]

Read my review of a Wester's Tune for our trucks Ray. It's titled "Wester's Tune on 2007 Sierra Denali" or something to that effect. Hopefully it helps.

[99silverado1500]

My dads GMC Sierra Duramax Allison has a abuse mode thing that when you rail the throttle to the floor it wont accelerate at that rate for 4 seconds it goes into a limp mode if thats what you want to call it, and after that it will accelerate normally, and the RPMs do jump up like that. A tune removes all of you problems.

[svensk]

I personally enjoy short onramps with my truck. I put it to the floor at 30mph and the back wheels break loose as it downshifts into first gear. My first gear ends with a 50mph redline shift of 5800rpms then snaps like a kick in the butt to 2nd.

Of course I have a wait4me performance tune running 92 octane with torque mgt. nuked along with abuse mode. With my 4l60e my 1-2 shift was the weakest part, now it feels like a manual banging through the gears under WOT. I could only imagine what the 6l80e would be like tuned.

[Raymond Lowe]

Read my review of a Wester's Tune for our trucks Ray. It's titled "Wester's Tune on 2007 Sierra Denali" or something to that effect. Hopefully it helps.

 

I'm quite happy with the power it has so I'm not sure a tune is the answer. An updated program for the transmission is what we need. I've read similiar complaints about this downshifting issue.

 

After all, how hard can it be? Your vehicle is going XX mph, you want to accelerate to pass or speed up quickly, you push the pedal down just over halfway to the floor, it should pick whatever gear that puts the RPM around 3-3500. This engine has tons of torque throughtout the entire range. So why does it pick a gear that awkwardly slams the rpm up around 5000? If you downshift manually to a gear where the rpm is around 3 grand and then roll onto the throttle, this truck is lightning fast, and smooth.

[ChrisNJ]

Raymond, I have problems with my 6sp too, but they are different than yours. Mine is an 07. I have the opposite problems, as mine performs poorly at light to mid throttle positions, basically keeping the r's way too low to move the truck the way i would like. I have to keep pressing more and more to get it to downshift, when it finally does, it is too late to get me up the hill, and now has to downshift two gears, it rocks, then i have to let off, and it goes back down to 1000-1200 rpm, this repeats itself all the way up a long hill, very annoying. I don't have any issues to get it to move out on an on ramp or passing, it does fine, for me. I agree 100% that the engine does not need anything, it's just the trans shift points and software are very bad (for me), unlike any gm trans i've every owned. I was told by gm that it's 'CAFE' and there is nothing they can do for me. but to me, it's wasting more gas going from rock-out to dog, and back 3 times up a long grade. I've haven't learned of any successfull trans tune yet, and subsequently have not gone there yet, living with it for now. Interestingly, my wifes new yukon xl denali, while still suffering from the dreaded upshift to 1000-1200 rpm, comes out of it very easily with just the slightest push of the pedal, in other words 'i want more, and it instantly and smootly comes out of 1200 rpm to the next gear propelling you like you want'. i have been told there is a very good/smart tuner around here, i just haven't had time to investigate. i'm hoping that a tuner can just eliminate the upshift to 1200 rpm, to say keep it in a gear a little longer, then upshift to say 1500-1800rpm, and all will be golden.

I wish gm would just put another button in, something inbetween econo mode and tow-haul. the tow-haul mode works great when towing, but is just way too aggressive for normal driving, and literally puts me in my seatbelt with it's engine-braking assist, and keeps the r's up way too high for driving non-agressive around town.

please report what you learn. i will too, just been crazy at work to get anything done on the truck front.

[Darkanion]

One complaint I've had about the 6spd transmission is that it seems to come out of 6th "too" quickly. My previous vehicle was an Acura TSX 6-speed. I got the Acura w/ the 6spd so *I* could decide which gear it was in and when. One of the things I always liked about it was that if I wanted to just nudge the gas a little and keep it in 6th gear and 'gently' get around someone, I could do that. It was torquey enough that it'd 'just go' without having to wind it up. On the other hand, if I wanted to haul-gas (and burn some extra), I could down-shift to 5th, 4th, 3rd, whatever and GO...

 

To me, the transmission program on the Sierra Denali seems to want to downshift a little "too" easily, while cruising down the highway. Some times, you just want to gain some speed, nudge the accelerator a little, and hear the exhaust growl a LITTLE without getting on it HARD and drawing a lot of attention to yourself. Some times, you're going up a small hill and you wish it'd "just pull a little more to maintain speed" without downshifting and all that b/s.

 

I was hoping the manual mode would help some with this, but it doesn't override the downshifts. In the few months I've had my truck, I've been learning some just how much I can 'nudge' the accelerator without having it downshift. But, it still seems a little touchy to me. One of the things I do like about the manual mode is that if I'm just easing back & forth to work (about 2-3 miles, at most, with too many red lights), I'll usually select manual and put it in 4th. That seems to cut down a lot on upshift/downshift and the occasional "lulls" when it doesn't seem sure exactly WHICH gear it should be in. I also catch myself doing it when I see a hill approaching ... or - for example - when I'm on the mountain roads in Colorado. Put it in 4th or 5th, keep the RPM up a little and listen to 'er sing, as I wind through the mountains...

 

Kinda makes me wish I was there, right now..

[sonjaab]

Quit pissin' and moaning !

 

Everybody cried and carried on about 6 speed, 6 speed, 6 speed !!!!!!!!!!!!!!!!!!!!!!

Well ya got it and this is how they work!

 

It sure takes some getting used to! Slow crusin' and its already in 5th so ya want to

step on it and get moving quickly and it drops down 2 or 3 gears.

Just smile and hang on!

 

I have been suprised several times with spinning tires, motor screaming and bouncing

off the rev limiter too!

 

Be careful what you wish for....................................

[MS3DALE]

Quit pissin' and moaning !

Everybody cried and carried on about 6 speed, 6 speed, 6 speed !!!!!!!!!!!!!!!!!!!!!!

Well ya got it and this is how they work!

I was kinda' thinkin' the same thing,I'll stick with my 4-speed.

Although I wouldn't mind having the "tap-up/tap-down" manual shift control ability.