07+ Sierra Denali Owners, What Do You Think?

mdrew · August 25, 2008

..........About your truck that is.

I have an 05 SD and am thinking about buying an 08 this week. I don’t spend much time on forums and I’m not up to speed on all the new gadgets, tunes, problems with the new drive trains, etc, etc that are discussed by folks who spend a fair amount of time on these forums…. I figured it might be a good idea to throw my situation out for input from folks who are up to speed. I spent some time with the search function, but there’s not a whole lot of talk about the SD’s, and they are somewhat unique.

The reason I ask is I’m still infatuated with my 05. For the past twenty years or so, I’ve had a routine where I buy a new truck every 24-36 months. I’ll put the own I have up for sale and put that money towards the new truck and then I cover the balance owed with cash that I set aside each month. In other words, I pay payments to myself into a separate account that I never touch till the day comes when I need it for the next vehicle. This keeps me in a new daily driver that I don’t have to tweak on. I’m just too darn busy to spend the few days off I get under my truck.

So anyway, I’ve had many different trucks over the past two decades including Ford and Dodge. Each time I buy a different truck, it isn’t long before I find myself ‘wanting’ a new truck because it has something new and cool that I think I need. When the new SD’s came out in 07 I was pretty jazzed over the 6.2 and six speed. I couldn’t stand the new look, particularly with the front end, but it’s grown on me over time, some……(I still don’t like it much). Then I test drove one for curiosities sake and wasn’t all that impressed. It just doesn’t have the pep that my 05 has. (I suspect that’s mostly due to the 3.42’s in the new trucks verses the 4.10’s in my 05). Because I liked my 05 so much, and I didn’t care for the new body style all the much and I wasn’t too impressed with the new truck’s performance, I decided a year ago I’d just keep my 05 and put some money into it (aftermarket shocks, rotors/calipers, headers, supercharger). Seeing how I no longer have a warranty, I may even pull the engine and give it a refresh with a different top end, cam and some port work.

……….well now I’m reconsidering again. Someone has offered me a fairly decent price on my truck (everyone knows I take very good care of my vehicles) and with the GM sale going on, I can pick up a new SD for a pretty good price. I took some more time test driving an 08 SD the other day and was less critical than before. Although my 05 still has the edge performance wise, I’m pretty sure the 08 can be woken up with a mild tune, or swap the gear sets out with 3.73’s if needed. I also like the interior of the 08 a wee bit more. I think I’ve just about talked myself into buying the 08…. But I figured I’d ask for input first.

Are there any known issues with the 6.2 or the six speed? What about the truck itself? Anything that I should consider? I heard the new body has a three piece bed? I have also heard (from a GM service tech) that the dealer can now determine if the vehicle has been tuned, even if you swap the PCM out with the OEM board. Can that be true?? Are there any glaring issues with these new trucks??

Thanks for reading and your time...........Michael

Darkanion · August 25, 2008

I've had my '07 SD since May '07. I'll have 19k miles on it here soon and the only time it has been back to the dealer was to buy a new "smooth" tailgate cap, because they're supposed to work better with the tonneau covers.

I haven't had any problems with the engine, transmission, or much of anything else. Every once in a while, the transmission shifts a little odd. But, over time, I've gotten used to. They're supposed to have a new 'program' for the transmission. But, I'm not sure I really want them jacking with that, since I've pretty much gotten used to how it is and how far I can push the accelerator down, going up a hill, before it downshifts, etc.

It will be going to the dealer, here soon, though.. I just got back from a vacation and I noticed that the driver's rear door handle (plastic covered 'chrome' apparently), is pulling loose from the body. I have no CLUE what caused that, as I don't jerk on the door handles or anything. But, it's definitely coming loose. Aside from that, no complaints, what so ever..

Here is a thread about SD's :

http://www.gm-trucks.com/forums/index.php?showtopic=71393

Here's one about the 6-spd transmission :

http://www.gm-trucks.com/forums/index.php?showtopic=70001

Good luck!

Bish · August 25, 2008

I've got an 08 YD and I came from an 01 Tahoe. Not the pickup but I'll give you my opinion.

18K miles since Christmas and I just had the right front strut replaced because it was blowing oil and squeaking. Other than that I have had no issues. Regarding performance, I am a bit surprised you didn't feel much difference compared to your 05. To me it is like night and day. I had a 5.3 4x4 3.73 gears in my Tahoe, catback, intake and tune. On my YD, I only have a tune and it rips compared to my Hoe. 1/4 mile time at 14.7 which I think is fantastic for a 6000lb brick. I also get 2mpg better with the extra 100+ HP. I think the six speed really helps with mileage as at 80mph I'm at 2K rpm.

Overall I'm extremely happy with the 08.

mdrew · August 25, 2008

Thanks guys….. I have to admit, that heated steering wheel and windshield wiper fluid are calling to me (I live in Alaska).

My 05 is pretty peppy. It came with the 345 hp 6.0. That engine coupled to 4.10 gear ratio makes for a truck with some serious snap off the line. It’s wonderful towing a trailer loaded with snowmachines too.

Darkanion · August 25, 2008

I also get 2mpg better with the extra 100+ HP. I think the six speed really helps with mileage as at 80mph I'm at 2K rpm.

That's very true. This last trip, there were long stretches of road out in West Texas and New Mexico, where I could set the cruise on 80 and the RPMs stayed just a hair under 2k, which kept it in the non-PE part of the tune (which gets better fuel economy).

I generally ran speed limit, plus five, for most of the trip... except for a stretch of West Texas that had a speed limit of 80.. I just stayed at the speed limit, for that stretch of road. I averaged better than 20 mpg for the whole 3k mile trip.

VMax2007 · August 25, 2008

Thanks guys….. I have to admit, that heated steering wheel and windshield wiper fluid are calling to me (I live in Alaska).

My 05 is pretty peppy. It came with the 345 hp 6.0. That engine coupled to 4.10 gear ratio makes for a truck with some serious snap off the line. It's wonderful towing a trailer loaded with snowmachines too.

Don't get too excited about the heated washer fluid. My truck has it (I live in MN) and it is pretty lame. Better than nothing I guess, but don't get your expectations too high is all I'm sayin'

mdrew · August 25, 2008

Is the wiper fluid warm enough to melt ice on the wipers?

How well does the six speed and fuel management work in the mountains? I have to drive through a mountain range about once a month. Actually, I’m surrounded by mountains. My 05 rarely drops out of OD when I travel about 70. I average 16.5mpg on these trips at that speed.

I noticed that the new trucks have eliminated the rear heater vents. Do ya’ll notice any problems with the back seating area getting warm?

I also noticed that they don’t offer a CD changer anymore, or at least the truck I test drove did not have this. Why would GM do that??

Darkanion · August 25, 2008

Is the wiper fluid warm enough to melt ice on the wipers?

How well does the six speed and fuel management work in the mountains? I have to drive through a mountain range about once a month. Actually, I'm surrounded by mountains. My 05 rarely drops out of OD when I travel about 70. I average 16.5mpg on these trips at that speed.

I noticed that the new trucks have eliminated the rear heater vents. Do ya'll notice any problems with the back seating area getting warm?

I also noticed that they don't offer a CD changer anymore, or at least the truck I test drove did not have this. Why would GM do that??

The 07 and 08 SD's don't have AFM. (I don't remember if the 09's will have it or not.) Depending on the grade, it would sometimes downshift to 5th (and every once in a while 4th, but that was uncommon). But, that really just depending on how steep the grade was, how fast I was going, and how much I wanted to maintain "that" speed.

I know you probably aren't familiar with the area, but from Safford, AZ, up through the Tonto National Monument area, up to Tuba City (near the Grand Canyon), I managed 20 mpg. There are some pretty good hills in there, especially between Safford and Flagstaff, up through the Tonto area..

From Tuba City to Cortez, Colorado (some up, some down, some hills, some flats), I managed 21.7. From Cortez, CO, up to Carbondale, down through Independence Pass, and down to Salida, CO (much more mountainous), I managed 21.6 mpg.

Oddly enough, I got better mileage in the mountain areas than I did on the flat lands. (Maybe my foot is heavier in the flat lands? )

I know this is going to sound like a smart-ass answer, but I'm never sitting in the back... So, no, I haven't noticed any problems with heating or cooling. The few times I've had people in the back seat, though, I've asked if they were getting enough air. No one has ever complained.

From what I've seen, you can either get the CD Changer OR the NAV system, but not a NAV w/ CD Changer. No clue why.. The "claim" is that a NAV CD Changer would take up too much room..??

mdrew · August 25, 2008

Wow….that’s pretty impressive numbers for a 400HP AWD truck. I think I can rest assured that the mileage will not go down from where I’m at now. I grew up in AZ (Cottonwood), so I went down memory lane and drove around AZ starting at Sierra Vista, up to the Canyon through the Slide Rock area and Flagstaff, through Tuba City and Monument Valley, back to 4 corners, through Shi-Low and back to SV where my parents live. The mountains aren’t quite as steep as here, but I do remember some fairly steep grades.

That’s a bummer about the fuel management. For some reason or other, I thought the SD’s had it but the Yukon Denali did not. It would seam from what you are getting that this truck doesn’t really need it though.

I see you have a tune. Do you know if what the GM service Tech told me is true? If you pop the OEM PCM back in before getting some service work, can they tell if you’ve been running a custom tune? The local dealerships up here are really cracking down tunes and warning folks to not buy one or use a programmer.

Darkanion · August 25, 2008

Just for clarification, mine is RWD, not AWD. So, the AWD ones will take a 1 to 2 mpg hit on the gas mileage. But, still, for a 400hp, 5000 lbs. truck... Yeah... It does pretty good on the mileage, IF you can keep your foot out of it and drive easy. It doesn't take much "spirited" driving to cut the mileage down pretty good.

I have mixed feelings about it "not" having AFM. On the one hand, the truck not having it is one less thing that can go wrong. On the other hand, it would be nice to get a little better mileage. BUT, if you drive it easier (where the AFM could actually kick in and do its thing, if you had it), you're going to save some fuel costs anyway. So, I'm not sure really how much "more" I would save if I did have AFM on mine.

When I bought the truck, though, I was actually glad that it didn't have AFM. I know most people haven't had issues with it. But, I'd rather have this incarnation in production longer, before I buy a vehicle with it on there. Let them work the bugs out, first.

I don't really have a good answer for you re: the tunes. I've "heard" that they can detect tunes. (Although, to be honest, I'm not sure HOW they could tell a truck had been tuned, if you swapped out the PCM, which is where the tune is located.) When I bought the Predator, people claimed dealers couldn't "see" the tune, even if it was still in there. So, I went with it... Being a computer guy, it didn't make sense to me that they couldn't see changes to the programming. But, the claim was that they couldn't see the tunes, so I bought the Predator and tuned my stock PCM.

I've thought about getting another PCM, to put a stock tune into. But, I haven't bit the bullet on that yet. Maybe before I buy HP Tuners and start messing with that... Maybe I'll get a stock-tuned PCM mated-up with this truck and then put "this" PCM back in it for tuning with HPT.

One thing to note : On the 6-spd transmission, the TCM is inside the transmission. So, for a tuner to remove Torque Management and most of the other so-called "nannies," the TCM will need to be programmed. There again, being a computer guy, I don't see how they could NOT tell that it had been reprogrammed.. So, that's a risk you'll have to calculate for yourself.

Now... From what I have read & heard about how GM is detecting tunes.. It's not that they are reading the PCM to see what the tune is actually doing, but that there is a 'counter' that keeps track of how many times a PCM has been flashed. So, basically, if their computers don't show that GM has ever reflashed the PCM and your PCM says it's been flashed 7 times, they know you've probably had a tune in there.

Supposedly, some people are claiming that GM is only doing that on the Duramax diesel engines. They're not as worried about the gas engines, so they "supposedly" haven't done the counters on the gassers. I'm not sure if I believe that or not. If you code a counter for one model PCM, it seems like it should be pretty stinkin' easy to take that same code and put it in other PCM's...

Bare minimum... In my mind... Even if you have a stock PCM with a stock tune and you swap it out, right before you take it in for service or warranty work... Unless everything else in the engine compartment is clean, they're going to see "dust everywhere, except... down... here.. where the PCM is.. hrmmmm.. Looks like someone has been messing with that." Then, that opens the door for them to 'suspect tampering' (or whatever) and take action on the warranty or whether or not they are going to cover the warranty work, if it's related to drivetrain.

Sorry for being so long winded... But, that's my 2 cents (plus a few) ...

Lincoln30 · August 25, 2008

I love my 08 SD and no real problems in the first 14K miles. My 08 stock is alot quicker then my modded 99 5.3 w/4.10s and it drives SO MUCH nicer. I love my 99 and I still have it but it nothing compared to the new one. The 99 pretty much just sits there and kills the battery now (I have it on a battery tender while I figure out how to let go of it).

BTW: the heated steering wheel is nice and even in TX I've gotten some use out of it. The downside is the wood part of the wheel gets really cold, so you need the heater but it warms the wood part very slowly...I wish they did this wheel in all leather.

mdrew · August 26, 2008

In regards to AFM, I think I might be confusing it with variable valve timing. I had thought variable valve timing allowed four cylinders to drop off when not under a load, which is what I had thought was referred to as Active Fuel Management. So for clarification’s sake, can someone tell exactly what AFM is?

Re; tunes. I ‘believe’, but by no means certain, that these trucks have additional memory that is no in the PCM. Or, I should say, that’s what the Tech was hinting at and that’s how they can tell if you’ve been messing with OEM tuning parameters.

Darkanion · August 26, 2008

AFM is the cylinder deactivation that you're thinking of. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy.

VVT allows the lift or duration or timing (some or all) of the intake or exhaust valves (or both) to be changed while the engine is in operation.

rvsahs · August 26, 2008

Just for clarification, mine is RWD, not AWD. So, the AWD ones will take a 1 to 2 mpg hit on the gas mileage. But, still, for a 400hp, 5000 lbs. truck... Yeah... It does pretty good on the mileage, IF you can keep your foot out of it and drive easy. It doesn't take much "spirited" driving to cut the mileage down pretty good.

I have mixed feelings about it "not" having AFM. On the one hand, the truck not having it is one less thing that can go wrong. On the other hand, it would be nice to get a little better mileage. BUT, if you drive it easier (where the AFM could actually kick in and do its thing, if you had it), you're going to save some fuel costs anyway. So, I'm not sure really how much "more" I would save if I did have AFM on mine.

When I bought the truck, though, I was actually glad that it didn't have AFM. I know most people haven't had issues with it. But, I'd rather have this incarnation in production longer, before I buy a vehicle with it on there. Let them work the bugs out, first.

I don't really have a good answer for you re: the tunes. I've "heard" that they can detect tunes. (Although, to be honest, I'm not sure HOW they could tell a truck had been tuned, if you swapped out the PCM, which is where the tune is located.) When I bought the Predator, people claimed dealers couldn't "see" the tune, even if it was still in there. So, I went with it... Being a computer guy, it didn't make sense to me that they couldn't see changes to the programming. But, the claim was that they couldn't see the tunes, so I bought the Predator and tuned my stock PCM.

I've thought about getting another PCM, to put a stock tune into. But, I haven't bit the bullet on that yet. Maybe before I buy HP Tuners and start messing with that... Maybe I'll get a stock-tuned PCM mated-up with this truck and then put "this" PCM back in it for tuning with HPT.

One thing to note : On the 6-spd transmission, the TCM is inside the transmission. So, for a tuner to remove Torque Management and most of the other so-called "nannies," the TCM will need to be programmed. There again, being a computer guy, I don't see how they could NOT tell that it had been reprogrammed.. So, that's a risk you'll have to calculate for yourself.

Now... From what I have read & heard about how GM is detecting tunes.. It's not that they are reading the PCM to see what the tune is actually doing, but that there is a 'counter' that keeps track of how many times a PCM has been flashed. So, basically, if their computers don't show that GM has ever reflashed the PCM and your PCM says it's been flashed 7 times, they know you've probably had a tune in there.

Supposedly, some people are claiming that GM is only doing that on the Duramax diesel engines. They're not as worried about the gas engines, so they "supposedly" haven't done the counters on the gassers. I'm not sure if I believe that or not. If you code a counter for one model PCM, it seems like it should be pretty stinkin' easy to take that same code and put it in other PCM's...

Bare minimum... In my mind... Even if you have a stock PCM with a stock tune and you swap it out, right before you take it in for service or warranty work... Unless everything else in the engine compartment is clean, they're going to see "dust everywhere, except... down... here.. where the PCM is.. hrmmmm.. Looks like someone has been messing with that." Then, that opens the door for them to 'suspect tampering' (or whatever) and take action on the warranty or whether or not they are going to cover the warranty work, if it's related to drivetrain.

Sorry for being so long winded... But, that's my 2 cents (plus a few) ...