Performance Mods For 07 Denali 6.2 Liter

chrisnigro · April 5, 2007

I was curious if anyone had any experience/feedback with the GM cat-back exhaust or the GM air box upgrades?

I am considering the Performance Exhaust:

http://www.gmaccessorydealer.com/details.asp?prod_id=69448

And the air intake:

http://www.gmaccessorydealer.com/details.asp?prod_id=66378

Before I go and dump a ton of $$$ - I would love to know if anyone has any results.

C & A s Dad · April 5, 2007

Chris, not to sound sarcastic because I do not mean it that way at all, but you have already dropped a ton of $$$ s on a very nice truck. From all I have read and researched you will gain very little HP from the cat back and will even loose some torque in the low to mid range. The same can be said for the intake tube. Some of them will not hurt your low end but many will. I am just not familiar with the GM kit. From the looks of the OE tube on the newer trucks, GM has removed a lot of restrictive tubes and mufflers that were present with the earlier models.

My suggestion would be that you leave the OE pieces in place and enjoy your new truck.

chrisnigro · April 5, 2007

Chris, not to sound sarcastic because I do not mean it that way at all, but you have already dropped a ton of $$$ s on a very nice truck. From all I have read and researched you will gain very little HP from the cat back and will even loose some torque in the low to mid range. The same can be said for the intake tube. Some of them will not hurt your low end but many will. I am just not familiar with the GM kit. From the looks of the OE tube on the newer trucks, GM has removed a lot of restrictive tubes and mufflers that were present with the earlier models.

My suggestion would be that you leave the OE pieces in place and enjoy your new truck.

I don't disagree - I did drop some $$. You don't sound sarcastic - It is realistic. This is what I have been battling with.

If some guy replied, that he was getting better mileage & better performance with no downside - That might push me off the fence.

That is why I was asking for some feedback - before I make any purchases.

Thanks for the reply!

C & A s Dad · April 5, 2007

Chris, you will see in my signature that I do have a TrueFlow CAI on my Yukon XL. I did this because it does retain the factory air box but replaces what then was an awful looking intake tube. Is the TF really less restricive? I cannot really answer this but it does clean up the underhood and looks much better. In my case, it helped my mid to upper range torque when pulling my camper and it improved my mileage almost 1 MPG. Not a significant amount but every little bit helps.

Again, from what I have seen of the new Intake tube on the later model trucks, it would appear to me that GM has removed any restriction that may have been in there with the previous models. If you get a chance to look under the hood of a 02 or 03 model, you will see what I mean.

BTW If you decide to look into a CAI, I am not a fan of an open element system. There are many of this forum that have them and are satisfied with them. However, there are some good systems out there that either retain the factory air box or offer a box of their own.

ChrisNJ · April 6, 2007

what's the rpm's at at 65mph? if around 2K or less, then I would think 3.73 rears vs the stock 3.42's would do wonders. but to switch front and rear will be around $2500.

RCman · April 6, 2007

what's the rpm's at at 65mph? if around 2K or less, then I would think 3.73 rears vs the stock 3.42's would do wonders. but to switch front and rear will be around $2500.

No way, maybe if you have the dealer/stealership do it!

BOTH sets of gears shouldn't run you more than 350-450 total. Master installed kits (if you replace ALL bearings and seals [pointless on an '07]) run about $110 a piece.

Totals:

$350-450 Gears

$110 (x2) Master install kits

$50-70 Quality Gear lube

$5-6 Tube of RTV

Taking the high side of this $746. If you shop around $605. Spend a few bucks on tools (if you don't have 'em already), do it yourself, learn something about your rig... done. Finished. Bingo.

Ok... so maybe you don't like to get your hands dirty. Most good shops would install gears for around $300-400 and axle... even then its still a FAR CRY from $2500...

ChrisNJ · April 6, 2007

what's the rpm's at at 65mph? if around 2K or less, then I would think 3.73 rears vs the stock 3.42's would do wonders. but to switch front and rear will be around $2500.

No way, maybe if you have the dealer/stealership do it!

BOTH sets of gears shouldn't run you more than 350-450 total. Master installed kits (if you replace ALL bearings and seals [pointless on an '07]) run about $110 a piece.

Totals:

$350-450 Gears

$110 (x2) Master install kits

$50-70 Quality Gear lube

$5-6 Tube of RTV

Taking the high side of this $746. If you shop around $605. Spend a few bucks on tools (if you don't have 'em already), do it yourself, learn something about your rig... done. Finished. Bingo.

Ok... so maybe you don't like to get your hands dirty. Most good shops would install gears for around $300-400 and axle... even then its still a FAR CRY from $2500...

Yes, the $2500 is what the dealer quoted me. I know it would be cheaper elsewhere, just reporting what I was told. And i don't mind getting my hands dirty, use to rebuild engines in my youth, but at 40 something with 2 kids and my own businees, just can't seem to get into any projects anymore, nor really want too. So about $1500 by a local shop sound right? I am interested because I was thinking about getting a denali, but already thinking that the 3.42's gotta go. And have any ideas about how to disable the AWD? If it's like our old classics with "auto-4wd", just always on, then maybe just an added switch can turn it off and on????

ridnlow · April 6, 2007

Do you have the 6l80e?? if so I wouldnt worry about gears..

Here are the ratios for the 6l80e

1st gear ratio 4.02

2nd gear ratio 2.36

3rd gear ratio 1.53

4th gear ratio1.15

5th gear ratio 0.85

6th gear ratio 0.67

As you can see with a 4.02:1 1st gear ratio, you dont need 4.10's to get the truck out of the hole.

6l80e 1st gear final drive ratio with 3.42's.

13.75:1

4l60e 1st gear final drive ratio

3.06 x 3.42= 10.47:1

in a 4l60e equipped truck you would need to run 4.56 to be close to the 6l80e trans with 3.42 gears.

I would definetely look at a tune.. Rumor has it GM has detuned these new motors more than ever..

ChrisNJ · April 6, 2007

Do you have the 6l80e?? if so I wouldnt worry about gears..

Here are the ratios for the 6l80e

1st gear ratio 4.02

2nd gear ratio 2.36

3rd gear ratio 1.53

4th gear ratio1.15

5th gear ratio 0.85

6th gear ratio 0.67

As you can see with a 4.02:1 1st gear ratio, you dont need 4.10's to get the truck out of the hole.

6l80e 1st gear final drive ratio with 3.42's.

13.75:1

4l60e 1st gear final drive ratio

3.06 x 3.42= 10.47:1

in a 4l60e equipped truck you would need to run 4.56 to be close to the 6l80e trans with 3.42 gears.

I would definetely look at a tune.. Rumor has it GM has detuned these new motors more than ever..

What about 4th gear vs. 6th gear comparison? I have 2 8.1's. one with a 4sp-4:10's that runs like a muscle car at every speed, step on it at a light and it rocks, step on it at 70mph and it still rocks. i also have a allison 6sp/3:73's, that runs soooo low rpm's in 6th, that it has to downshift twice to get it moving at high speed, and the double downshift takes forever.

ridnlow · April 6, 2007

6l80e

1800 rpm, 3.42 gears, 0.67:1 OD and 30" tires gives you 70 mph cruise.

4l60e

1900 rpm, 3.42 gears, .70:1 OD gear 30" tires gives you a 70 mph cruise.

You get good acceleration and gas mileage to boot

Ive never looked at a 6l80e in tuning software but I imagine you could get it where say 70mph and under it wont shift in 6th.. that when when you kick down on it it will go to 4th.. just something to think about

Big Tool · April 6, 2007

Do you have the 6l80e?? if so I wouldnt worry about gears..

Here are the ratios for the 6l80e

1st gear ratio 4.02

2nd gear ratio 2.36

3rd gear ratio 1.53

4th gear ratio1.15

5th gear ratio 0.85

6th gear ratio 0.67

As you can see with a 4.02:1 1st gear ratio, you dont need 4.10's to get the truck out of the hole.

6l80e 1st gear final drive ratio with 3.42's.

13.75:1

4l60e 1st gear final drive ratio

3.06 x 3.42= 10.47:1

in a 4l60e equipped truck you would need to run 4.56 to be close to the 6l80e trans with 3.42 gears.

I would definetely look at a tune.. Rumor has it GM has detuned these new motors more than ever..

What about 4th gear vs. 6th gear comparison? I have 2 8.1's. one with a 4sp-4:10's that runs like a muscle car at every speed, step on it at a light and it rocks, step on it at 70mph and it still rocks. i also have a allison 6sp/3:73's, that runs soooo low rpm's in 6th, that it has to downshift twice to get it moving at high speed, and the double downshift takes forever.

That's the same way with the denali, it's just part of a 6sp i believe which i'm not completely fond of. an extra OD is great for mpg, but driveability wise isn't the greatest thing. with the 4.10's going 70 with my 6.0 i can just lean on the gas without downshifting and it will quickly climb to 100mph. My dad's denali with the 6.2 and 6sp has to drop to atleast 5th to keep up and most of the time it goes to forth. So imo the 6sp isn't always the greatest option...

svensk · April 6, 2007

Yeah, but he's gonna get to 100 faster than you with his 6speed. I'd put money on that.

I didn't think you could change out to 3.73 axel on a denali because of how complex the AWD is. I think it would be quite a pain the arse to disable it and make it a 4x4 or 2wd at the easiest. It doesn't use a transfer case like the 4x4 it has one more complex gizmos that gives a 60/40 split full time to both axels. I would leave it alone and get a tune.

C & A s Dad · April 6, 2007

what's the rpm's at at 65mph? if around 2K or less, then I would think 3.73 rears vs the stock 3.42's would do wonders. but to switch front and rear will be around $2500.

No way, maybe if you have the dealer/stealership do it!

BOTH sets of gears shouldn't run you more than 350-450 total. Master installed kits (if you replace ALL bearings and seals [pointless on an '07]) run about $110 a piece.

Totals:

$350-450 Gears

$110 (x2) Master install kits

$50-70 Quality Gear lube

$5-6 Tube of RTV

Taking the high side of this $746. If you shop around $605. Spend a few bucks on tools (if you don't have 'em already), do it yourself, learn something about your rig... done. Finished. Bingo.

Ok... so maybe you don't like to get your hands dirty. Most good shops would install gears for around $300-400 and axle... even then its still a FAR CRY from $2500...

Hey Bill, this is good info being batted back and forth but we do our best not to use the term "stealership" here. There are some really great Techs on this forum who provide a lot of good info and many of them make their living at GM Dealerships. I realize there are some less than honest Dealerships out there but I like to think the good ones far outweigh the questionable ones. I am not the "Forum Police" I just like having these Techs around this forum because of their knowledge.

ChrisNJ · April 6, 2007

6l80e
1800 rpm, 3.42 gears, 0.67:1 OD and 30" tires gives you 70 mph cruise.

4l60e

1900 rpm, 3.42 gears, .70:1 OD gear 30" tires gives you a 70 mph cruise.

You get good acceleration and gas mileage to boot

Ive never looked at a 6l80e in tuning software but I imagine you could get it where say 70mph and under it wont shift in 6th.. that when when you kick down on it it will go to 4th.. just something to think about

1800 and 1900 are way to low for responsiveness. good for gas, but i could care less about mpg. my 4sp-4:10's ran at 2500 at 70, and it was great. had a 6.0 with this that went pretty good with same, have an 8.1 with this setup that is just awesome. a tune would probably fix it. my 8.1-6sp-ally-3.7s's is similiar to your result above and i don't like it, i keep it manually selected to 5th on the highway and it's ok, but still at 2000 rpm is too low to get it moving, have to go to 4th, and the ally seems to take forever to downshift. so i still believe the 6sp is not good for me, maybe for most. i am frustrated, these trucks keep getting worse for me, no 8.1, now a 6sp, then they put a decent 6.2 in at least one of their trucks, and it's chocked with 3.42's, and a stupid AWD that I don't want. and C&A is correct, i like my dealership, they take care of me like no other, and in my time in life I need service more than i'm worried about costs. as of right now, my current 8.1-HD-pick-up is the best for me, but it rides like hell. the denali seems to be the next best choice, but has the gearing and AWD problem, and haven't driven one to report. the best truck i've ever owned, and still do is my wife's Burb-8.1-4sp-4:10's. it has the 8.1 stuffed in the non-HD frame. it has power now, everywhere, and rides good too. i can only wait, as gm typically comes out with niche trucks 2 years after a new intro. we'll see.

chrisnigro · April 6, 2007

Wow.. We really got derailed here! I am looking for feedback on bolt-on mods. I'm not cracking my pumpkins open and bustin out my feeler guages for this project.