2500 vs 3500 torque limiting?

H1ghlndr · February 12, 2020

I just bought a 3500HD AT4 Duramax that dealer had already coming in on order. Should be here in a few days. I had a previous 2015.5 Duramax 2500HD. Only differences I can seem to find are 12" rear-end, rear helper spring and apparently no torque limiting on 3500s? Everything else seems same.

Can anyone confirm / update these for me?

MTU Alum · February 12, 2020

The differences are three stage leaf spring, rear shock, 12 in rear axle, and 80 psi rear tire pressure for diesel trucks. Gas trucks stay with 11.5 rear axle.

12in rear axle allows for full torque in first gear

#iworkforGM

dlockwood26 · February 12, 2020

Your 2015.5 was also LML. The new ones are LP5. Bigger horse.

H1ghlndr · February 13, 2020

Thank you!

redwngr · February 13, 2020

FWIW, L5P came for 2017 model year.

L5P with 10 speed came for 2020.

newdude · February 13, 2020

On 2/12/2020 at 6:17 AM, H1ghlndr said:

I just bought a 3500HD AT4 Duramax that dealer had already coming in on order. Should be here in a few days. I had a previous 2015.5 Duramax 2500HD. Only differences I can seem to find are 12" rear-end, rear helper spring and apparently no torque limiting on 3500s? Everything else seems same.

Can anyone confirm / update these for me?

I've searched high and low about this and I can't find ANY documented proof of the "3500hd is the only one that gets max power in 1st gear".

Nothing from GM in any press releases, nothing in the Chevrolet training, nothing anywhere. Where do people keep getting this from?

All I've ever been able to find is from here: https://media.chevrolet.com/media/us/en/chevrolet/home.detail.html/content/Pages/news/us/en/2019/feb/0205-silverado-hd-2020.html

Quote

New Allison® 10-speed transmission matched with proven Duramax 6.6L Turbo-Diesel
“The 6.6L Duramax diesel and Allison® transmission is a legendary combination in the HD truck market with proven durability and capability that our customers expect,” said McQuaid. “For 2020, we made the combination even better and upgraded nearly every driveline component. As a result, we will deliver all 910 lb-ft of torque to the ground in first gear.”

It does NOT state any difference in models.

MTU Alum · February 13, 2020

There is a difference and this quote was probably taken out of context. The differences are small and most people couldn't tell the difference.

#iworkforGM

joelabq · February 14, 2020

I'm pretty sure the 12" rear is only in the drw. So that component, if shopping in the srw, will not be any different.

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jjackkrash · February 14, 2020

https://www.gmc.com/gmc-life/trucks/sierra-heavy-duty-purpose-built-to-trailer-like-pro

"This upgraded driveline includes new, larger, more robust front and rear axles, a standard 11.5-inch ring gear on 2500HD models, and a massive 12-inch ring gear on 3500HD diesel models. Additionally, the Sierra 3500HD does not need to limit torque in first gear, allowing it to transmit all of its trailer-pulling power to the wheels from a standing start."

jjackkrash · February 14, 2020

55 minutes ago, joelabq said:

I'm pretty sure the 12" rear is only in the drw. So that component, if shopping in the srw, will not be any different.

Sent from my LG-H932 using Tapatalk

I have seen several conflicting or at least vague reports on this from various gm sources, but believe based on mounting evidence that the 12" is on both the SRW and DRW 3500s. But I wouldn't bet pink slips on it either.

Edited February 14, 2020 by jjackkrash

MTU Alum · February 14, 2020

12 inch is on both srw and drw 3500.

#iworkforGM

CRApex · February 14, 2020

9 hours ago, jjackkrash said:

I have seen several conflicting or at least vague reports on this from various gm sources, but believe based on mounting evidence that the 12" is on both the SRW and DRW 3500s. But I wouldn't bet pink slips on it either.

This is from an artice with an Engineer from the HD truck team..Agree, lot's of conflicting info. II went and looked at a 2500 Dmax and 3500 Dmax, both SRW crews at the dealer. Parked right along side each other and the axles atleast looked identical. Not sure if there would be a visible difference between the 2500 and 3500. Also, why limit torque at all on an SRW if most people won't notice? The below article kind of suggests only the 3500 DRW would have no torque limiting due to the 12" ring gear. However, MTU is stating the SRW also gets the 12" ring which is in dispute with what the HD team engineer (Mcquaid) stated in the below exerpt. Very confusing info and GM really needs to clear this up.

Here is an exerpt from the article:

Beefier Axles
Having the gearing, torque, and cooling to handle the demands of trailering heavy loads is one thing, but those are of no relevance if the rest of the drivetrain can't handle the forces needed to get the power to the ground.

GM's engineers beefed up the size of the '20 HD's drivelines by 30 percent. While the single-rear-wheel 2500/3500HDs retain the same American Axle & Manufacturing (AAM) 11.5-inch ring gear in the rear axlehousings and 14.1x1.3-inch disc brakes as '19, the 3500 dual-rear-wheel (DRW) models now run AAM's massive rear differential with a 12-inch ring gear, tree trunk-sized 4.25-inch axletubes, and 14x1.6-inch brake rotors front and rear.

Per article with Chief Engineer for HD trucks:

With all of the upgrades, McQuaid says 2020 Chevy HD trucks will deliver all 910 lb.ft. of torque to the pavement in the first gear. The transmission is also capable of first gear lockup with all 910 lb. ft.

dadztoy · February 14, 2020

6 minutes ago, CRApex said:

This is from an artice with an Engineer from the HD truck team..Agree, lot's of conflicting info. II went and looked at a 2500 Dmax and 3500 Dmax, both SRW crews at the dealer. Parked right along side each other and the axles atleast looked identical. Not sure if there would be a visible difference between the 2500 and 3500. Also, why limit torque at all on an SRW if most people won't notice? The below article kind of suggests only the 3500 DRW would have no torque limiting due to the 12" ring gear. However, MTU is stating the SRW also gets the 12" ring which is in dispute with what the HD team engineer (Mcquaid) stated in the below exerpt. Very confusing info and GM really needs to clear this up.

Here is an exerpt from the article:

Beefier Axles
Having the gearing, torque, and cooling to handle the demands of trailering heavy loads is one thing, but those are of no relevance if the rest of the drivetrain can't handle the forces needed to get the power to the ground.

GM's engineers beefed up the size of the '20 HD's drivelines by 30 percent. While the single-rear-wheel 2500/3500HDs retain the same American Axle & Manufacturing (AAM) 11.5-inch ring gear in the rear axlehousings and 14.1x1.3-inch disc brakes as '19, the 3500 dual-rear-wheel (DRW) models now run AAM's massive rear differential with a 12-inch ring gear, tree trunk-sized 4.25-inch axletubes, and 14x1.6-inch brake rotors front and rear.

Per article with Chief Engineer for HD trucks:

With all of the upgrades, McQuaid says 2020 Chevy HD trucks will deliver all 910 lb.ft. of torque to the pavement in the first gear. The transmission is also capable of first gear lockup with all 910 lb. ft.

So this article is stating that the "dually" is the only '20 with a 12" ring gear...………????? Is this confirmed?

CRApex · February 14, 2020

1 minute ago, dadztoy said:

So this article is stating that the "dually" is the only '20 with a 12" ring gear...………????? Is this confirmed?

That what's the article say's if you choose to believe it. MTU is stating otherwise. Again when I looked at the 2500 and 3500 diesel SRW's side by side, the axles "looked" the same. Now we need to compare a dually axle, visually, to SRW to see if there is a visual difference. Again, it would be nice if GM would clear this up officially with specs on the website.

dadztoy · February 14, 2020

1 minute ago, CRApex said:

That what's the article say's if you choose to believe it. MTU is stating otherwise. Again when I looked at the 2500 and 3500 diesel SRW's side by side, the axles "looked" the same. Now we need to compare a dually axle, visually, to SRW to see if there is a visual difference. Again, it would be nice if GM would clear this up officially with specs on the website.

As I read it, all the 3500 Diesel models will be a 12"....

"Across the board, rear axles have larger, stronger components than ever before in order to both increase gross axle weight ratings (GAWR) and effectively deliver as much torque to the ground as possible. This upgraded driveline includes new, larger, more robust front and rear axles, a standard 11.5-inch ring gear on 2500HD models, and a massive 12-inch ring gear on 3500HD diesel models. Additionally, the Sierra 3500 Heavy Duty does not need to limit torque in first gear, allowing it to transmit all of its trailer-pulling power to the wheels from a standing start."