2018 GMC Denali swapping to 4.11 Gearing

[M1ck3y]

4.11's with an 8spd... You'll use a lot more fuel because your going to have to drive around in auto full time.

[ehediger]

52 minutes ago, DHeinze said:

Funny thing. This is my second wife. The first was conservative did well raising the kids. The second one a little crazy and doesn't want kids..... she graduates college this fall.... I may be in for a big surprise.....

So what is your opinion of 4:11 for just putting on larger tires? Probably 33’s. The 6.2  with 3:23 gears runs considerably better than my 15 w/ the 5.3, but I’d like a little more instant power.

 

Thanks for the help!

Edited November 2, 2018 by ehediger

[DHeinze]

15 minutes ago, ehediger said:

So what is your opinion of 4:11 for just putting on larger tires? Probably 33’s. The 6.2  with 3:23 gears runs considerably better than my 15 w/ the 5.3, but I’d like a little more instant power.

 

Thanks for the help!

My truck is stock with 22" rims and 3" of side wall on both sides making me 28". The 6.2 will spin the back ones all the way to the tire shop. There is a you tube video explaining tire size increases to gearing changes. I stumbled across it searching gearing swaps on GMC's. I think the guy had a early model Toyota with 33" on it. It was pretty informative. 

[DHeinze]

41 minutes ago, M1ck3y said:

4.11's with an 8spd... You'll use a lot more fuel because your going to have to drive around in auto full time.

You may be right...

[DHeinze]

Just now, DHeinze said:

You may be right...

The best 25 miles we ever got in the truck was 37.5mpg. Its nuts what a tailwind can do

[Darksky]

Let me throw a small wet blanket on your gear change fire...

Based on experience with my 2015 6.2 8speed High Country, I’m assuming that your 6.2 8speed Denali has the 9.76 inch rear differential, as does mine. GM installed the slightly beefier rear ends in these trucks, purportedly because of the bigger engine and the towing loads trucks equipped in this manner may see. As a 6.2 liter driver I’m “certain” that the strength of the 9.76 over the 9.5  is “absolutely” needed as I’m burning up the quarter mile daily. Whether or not it’s really necessary is a subject for further debate. 

 

That said, if you look at the gear supplier’s websites. You will see that the shortest gear available for the 9.76 inch diff is the 3.73 if you go to a shorter (numerically higher) gear such as the 4.10 or 4.56 you have to spend an additional +/- $300 bucks for a bearing set. That nearing set is actually an adapter to allow you to run the slightly physically smaller gear set which was meant for the 9.5 inch differential.

 

While this is not the end of the world, it does bear mentioning. You are slightly downgrading the internals of your “massive” 9.76 inch differential to those of the smaller (some might say puny) 9.5 inch differential.

 

It seems that the market for these gears is not large enough to merit the manufacture of more choices for the 9.76 inch differential yet.

 

*Please note: my tongue in cheek comments regarding the  big engine/little engine, giant/puny are just that. I read a comment in a thread earlier today about the “Dale” wannabes in their pathetic 6.2 liter “race” trucks and their general lack of good sense. I didn’t intend to push anyone’s hot button and I don’t think we need to be getting angry at one another over displacement.

 

I have a 2015 6.2 High Country. It was sitting on the lot amongst the 2016 trucks, I made what I think was a good deal on it. It is pretty and it runs well. I, like you want it to do even better. I have driven and owned an underpowered truck in the past and it suuu-uuuucked. 

 

When I regear, I intend on staying with the 3.73 gears, not a big change, I know. I would like to stay with the heavier 9.76 inch set.  I have upsized my tires to 34x12.50 R18 from stock, so hopefully the 3.73 is enough.

 

Tell me me why I’m right or wrong.

[ehediger]

Small wet blanket my ass! [emoji1787].

I guess 3:73s it is.

Your a genius gump, thank you for the response..by the way, there is no replacement for displacement.


Sent from my iPad using Tapatalk

[DHeinze]

On 11/2/2018 at 3:28 AM, Darksky said:

Let me throw a small wet blanket on your gear change fire...

Based on experience with my 2015 6.2 8speed High Country, I’m assuming that your 6.2 8speed Denali has the 9.76 inch rear differential, as does mine. GM installed the slightly beefier rear ends in these trucks, purportedly because of the bigger engine and the towing loads trucks equipped in this manner may see. As a 6.2 liter driver I’m “certain” that the strength of the 9.76 over the 9.5  is “absolutely” needed as I’m burning up the quarter mile daily. Whether or not it’s really necessary is a subject for further debate. 

 

That said, if you look at the gear supplier’s websites. You will see that the shortest gear available for the 9.76 inch diff is the 3.73 if you go to a shorter (numerically higher) gear such as the 4.10 or 4.56 you have to spend an additional +/- $300 bucks for a bearing set. That nearing set is actually an adapter to allow you to run the slightly physically smaller gear set which was meant for the 9.5 inch differential.

 

While this is not the end of the world, it does bear mentioning. You are slightly downgrading the internals of your “massive” 9.76 inch differential to those of the smaller (some might say puny) 9.5 inch differential.

 

It seems that the market for these gears is not large enough to merit the manufacture of more choices for the 9.76 inch differential yet.

 

*Please note: my tongue in cheek comments regarding the  big engine/little engine, giant/puny are just that. I read a comment in a thread earlier today about the “Dale” wannabes in their pathetic 6.2 liter “race” trucks and their general lack of good sense. I didn’t intend to push anyone’s hot button and I don’t think we need to be getting angry at one another over displacement.

 

I have a 2015 6.2 High Country. It was sitting on the lot amongst the 2016 trucks, I made what I think was a good deal on it. It is pretty and it runs well. I, like you want it to do even better. I have driven and owned an underpowered truck in the past and it suuu-uuuucked. 

 

When I regear, I intend on staying with the 3.73 gears, not a big change, I know. I would like to stay with the heavier 9.76 inch set.  I have upsized my tires to 34x12.50 R18 from stock, so hopefully the 3.73 is enough.

 

Tell me me why I’m right or wrong.

To be honest it is only for pulling our travel trailer. Not looking for a hotrod or a fast truck. The only reasoning for going to 4.10 was if you going to spend the money for 3.73 why not the 4.11 if I'm in the mountains all the time pulling it. I'm fine with 3.73 gearing i think it will accomplish the same end goal. Just didn't realize it was only designed for the 9.5. I don't turn wrenches for a living. I will always ask a questions. I have learned that there are dumb questions or answers. 

[DHeinze]

On 11/3/2018 at 2:56 PM, ehediger said:

Small wet blanket my ass! .

I guess 3:73s it is.

Your a genius gump, thank you for the response..by the way, there is no replacement for displacement.


Sent from my iPad using Tapatalk

Agreed!

[powerhaulic]

Having owned an '17 SLT max tow 6.2, I would think the 3.73 would be perfect for towing.

We towed an 8800# travel trailer NY to Fla several times, with good results but 3,73 would have been perfect.

If only tuning was readily available for the '17s and the 8spd, that truck would probably still be in the garage next to the L5P........lol

Too early torque converter lock-up (and shudder) was the only real issue

Edited November 9, 2018 by powerhaulic
typo

[DHeinze]

On 11/5/2018 at 4:49 PM, powerhaulic said:

Having owned an '18 SLT max tow 6.2, I would think the 3.73 would be perfect for towing.

We towed an 8800# travel trailer NY to Fla several times, with good results but 3,73 would have been perfect.

If only tuning was readily available for the '18s and the 8spd, that truck would probably still be in the garage next to the L5P........lol

Diablo has it for the 18' not a lot of options for the 8 SPD TCM. they have broke through the algorithms to unlock it.

The 2017 TCM is still a mystery with no unlock.

I spent some time on the phone with them before ordering it after asking the question in their forum. When you plug it in it will read the programming. You then email the file it saves for the ECM and the TCM to them and within 24 hours they return it jailbroken. Plug it back up and your in. 

[M1ck3y]

On ‎08‎/‎11‎/‎2018 at 7:47 PM, DHeinze said:

Diablo has it for the 18' not a lot of options for the 8 SPD TCM. they have broke through the algorithms to unlock it.

The 2017 TCM is still a mystery with no unlock.

I spent some time on the phone with them before ordering it after asking the question in their forum. When you plug it in it will read the programming. You then email the file it saves for the ECM and the TCM to them and within 24 hours they return it jailbroken. Plug it back up and your in. 

Daiblo doesn't have tcm tuning for 18's. just engine tuning for 17's and 18's

Edited November 10, 2018 by M1ck3y

[DHeinze]

That is what I'm getting from the forum at Diablo. They responded that they CV old access the 18 but not the 17. 

[DHeinze]

Sorry could access the 18

[DHeinze]

On 11/9/2018 at 8:45 PM, M1ck3y said:

Daiblo doesn't have tcm tuning for 18's. just engine tuning for 17's and 18's

HEre is the String from Diablo for the 8 SPD tranny Tune. 

https://forum.diablosport.com/viewtopic.php?f=62&t=62603