Attention Denali Owners!

Big Tool · January 24, 2008

Since my dad got his 07 denali XL, something has alway just seemed extremely wrong with the way the transmission shifted and the programming of the fuel deliver. For example going 40mph you hit the gas the tranny would dowshift, and then bog down for a couple secods then there would be a sudden rush of power. If you stomped it to the floor it would just haul ass and it wasn't so noticable.

Another problem since having the denali is the cruise control. If you are on the interstate with the cruise on the trany is constantly shifting on every tiny hill. By shifting i don't just mean going to 5th which would be ok, but it would go all the way down to 4th and scare the crap out of everybody in the truck.

The shifting and horrible power delivery were so bad, my dad actually bought a tundra. "not just b/c of those reasons but they did contribute"

Since my dad bought the tundra the Denali has became the family loaner vehicle. My Sierra had a couple warranty issues so that meant i was going to be in the denali for a week or so. When i first started driving it, i started thinking about what might cause the issues and the cheapest thing to try was premium fuel. The first tank was pretty much normal. After the first tank or so i imagine the computer had enough time to readjust itself the timing, fuel mixture etc for the premium fuel and it is amazing.

Now when you step on it there is absolutely no delay or bogging down what so ever. You simply had to drive the truck before and after to appreciate the difference. Also since switching to premium while crusing on the interstate it never shifts out of OD. I couldn't believe it. I've taken it on several 50+mile trips in some of the hillies interstate driving around my area and it never shifts out of OD. Only once or twice has it shifted out of 6th gear, and my dad's tundra does the same thing on the same hills.

Today i drove the denali and the Tundra back to back and the denali feels much more powerful than the Tundra, not to mention is much smoother. I hate to surrender the denali back over to my parents, but they need it more than i do. "Sister is pregnant and she and my mom always ride in the denali instead of my moms cts"

Moral of the long post is if you spent the big $$$ on a denali do the right thing and feed it some high octane fuel. Your denali will thank you for it. Hopefully if any of you are having problems like ours it will have the same effect.

btw denali has over 70,000 miles on it now and going stronger than ever.

tobias · January 24, 2008

70k in one year, d**n.

Bostonsfavson · January 24, 2008

Thanks for the info Ed. I always run 93 in my truck as the octane certainly has a noticeable effect on these engines. There's a reason that premium fuel is recommended; the lower octane fuel really causes the computer to retard the timing.

X-man · January 24, 2008

Thanks for the information, I have been wondering whether to use regular or not. I guess the answer is not.

GM also recommends using top tier fuels. Around here Arco regular is around $2.90 whereas top tier Chevron premium is around $3.50. That's quite difference. Unfortunately, I didn't think of this when I bought my Sierra Denali. I guess I'll be keeping my old Caprice for a daily driver.

Big Tool · January 24, 2008

70k in one year, d**n.

It's been parked for the past few months since my dad got the Tundra. My dad is very rough on vehicles and dosen't give a crap how bad they get beat up, on top of that he's constantly on the road between South MS, and South Tx. The denali was a wreck when he bought the Tundra, now the denali is spotless and lookin good, and the Tundra looks like Azz. The rear bumbper on the tundra is bent in from hitting a pine tree, and the drivers side rear bed panel is folded in from hitting a metal pole at out deer camp. He's pretty hardcore and can afford to not worry about screwing up a truck I didn't take after that part of his behavior luckily for my sierra and all my other trucks of the past. Everybody knows if that if i have a truck it has been taken good care of.

The denali is getting pampered by my mom and sister. The roughest thing they do is scrub a curb trying to get into the mall parking lot lol...

tobias · January 24, 2008

70k in one year, d**n.

It's been parked for the past few months since my dad got the Tundra. My dad is very rough on vehicles and dosen't give a crap how bad they get beat up, on top of that he's constantly on the road between South MS, and South Tx. The denali was a wreck when he bought the Tundra, now the denali is spotless and lookin good, and the Tundra looks like Azz. The rear bumbper on the tundra is bent in from hitting a pine tree, and the drivers side rear bed panel is folded in from hitting a metal pole at out deer camp. He's pretty hardcore and can afford to not worry about screwing up a truck I didn't take after that part of his behavior luckily for my sierra and all my other trucks of the past. Everybody knows if that if i have a truck it has been taken good care of.

The denali is getting pampered by my mom and sister. The roughest thing they do is scrub a curb trying to get into the mall parking lot lol...

When a Denali becomes the family loaner, I'd say he probably can afford not to worry. You thought about taking it over for good?

Big Tool · January 24, 2008

Thanks for the info Ed. I always run 93 in my truck as the octane certainly has a noticeable effect on these engines. There's a reason that premium fuel is recommended; the lower octane fuel really causes the computer to retard the timing.

That's what it felt like to me the timing that is. When i would hit the gas it was like it temporairly flooded then it would lean out and the power would build up suddenly.

ChrisNJ · January 24, 2008

There is a TSB out for all nbs 6sp's that fixes most of the trans shifting issues. Came out a couple months ago and has made the Denali even better. You have to ask for it though, the dealer will not put it in unless you complain about the trans shifting issues. And will take a couple tanks of gas to really work, but I like it a lot better now. Mine worked noticably better right away, but with 1K on it now, it's getting much much better.

Raymond Lowe · January 25, 2008

I have had similiar experiences with premium. The truck would hold those gentle inclines in 6th instead of bogging down which really makes an improvement in the driveability. It makes me wonder if a Westers tune might help this even more.

Starting to lean towards the tranny update. Driving around town, the Denali upshifts great. I was quite happy with the shifting. A few days ago, I went on a trip. It's the highway where the tranny programming is the most annoying. It just doesn't react properly on hills or passing. Your doing 40-45 and you need to accelerate quickly into an opening in the next lane and that's where it will fall on it's face, pause, downshift 2 gears lower than it needs with a big jerk, race the crap out of the engine, and you don't really take off because the timing has backed way off due to abuse management.

Curious if the update has addressed this shortcoming.

ChrisNJ · January 25, 2008

Much agree that the 6sp has had some issues with certain situations. Since my TSB update it feels a lot better, closer to a manual trans feel than any prior auto-trans i've owned. Still not the instant power avail at any speed with the 8.1-4sp-4:10, but that's not he 6sp's fault. Throttle position and response is much improved. Again, still not perfect, but I am satisfied, which is tough for this brain.