HD towing package on my 2017 - transmission replaced - does HD part# matter?

[ers37]

just had the 6L80 replaced with a rebuilt.... 120k miles.

Our 4WD 2017 has the HD tow package (RPO code: NHT)... my understanding is the 6L80 tansmission is actually a different part number than the standard 6L80. I'm not sure the difference, but seems to me it's the cooling fluid is routed different in the HD-variant vs. the standard(?)... but my question is this:

***Does it matter to be certain that the replaced transmission is the "HD" version? I personally can't figure out a way to verify myself what part#/version was replaced with.

[if consensus is it's a non-consequentional difference, then I won't bother; If it's a consequential difference, then how can a layman tell the difference in physical parts?]

 

[Doubeleive]

just had the 6L80 replaced with a rebuilt.... 120k miles.

Our 4WD 2017 has the HD tow package (RPO code: NHT)... my understanding is the 6L80 tansmission is actually a different part number than the standard 6L80. I'm not sure the difference, but seems to me it's the cooling fluid is routed different in the HD-variant vs. the standard(?)... but my question is this:

***Does it matter to be certain that the replaced transmission is the "HD" version? I personally can't figure out a way to verify myself what part#/version was replaced with.

[if consensus is it's a non-consequentional difference, then I won't bother; If it's a consequential difference, then how can a layman tell the difference in physical parts?]

nht is just a enhanced cooling package, a smidge bigger radiator basically, if it was a different transmission it would be a 6l90
**edit, not 100% sure on that though

 

[ers37]

I feel a little less concerned then... good. ***But then why then is there a distinctly different transmission part#, if it's not mechanically differnt?
--- normal: 24279064 (or: 19431764)
--- w/ HD towing package: 24279065 (or: 19431766)

 

[Joseph Garcia]

Ain't AI fun? Just ask (the answer may not be correct in every instance, though).

Transmission part numbers 24279064 and 24279065 are both associated with the GM 6L80 6-speed automatic transmission. The primary difference between these two specific part numbers appears to be related to the vehicle applications they are designed for and potentially certain optional configurations.

Here's a breakdown of the differences:

24279064: This transmission is typically associated with vehicles like the 2014-2019 Chevy Silverado 1500, 2014-2018 GMC Sierra 1500, 2015-2017 GMC Yukon, 2015-2018 GMC Yukon XL, 2015-2019 Chevy Tahoe, and 2015-2018 Chevy Suburban, often in 4WD configurations with a 5.3L engine. It may or may not include the tow package.

24279065: This transmission is more specifically linked to vehicles with a tow package (RPO code NHT), like the 2016 GMC Yukon XL 1500, 2016 GMC Sierra 1500, 2015 GMC Sierra Denali 1500, 2014 Chevrolet Silverado 1500, 2014 GMC Sierra 1500, 2015 Chevrolet Silverado 1500, 2015 GMC Sierra 1500, 2015 Chevrolet Tahoe, and 2016 GMC Yukon.

In essence, while both are 6L80 6-speed automatic transmissions, the difference between these two part numbers likely boils down to the specific vehicle configuration (like the presence of a tow package) and potentially minor internal variations to accommodate those differences, according to B-Parts. Therefore, it's crucial to confirm the specific year, make, model, trim, and engine of your vehicle when purchasing a replacement transmission to ensure compatibility.

 

[Doubeleive]

@NickTransmissions might have a more definitive answer.
I am not sure how much difference there is internally, such as maybe a different torque converter, clutch packs, etc.

 

[swathdiver]

just had the 6L80 replaced with a rebuilt.... 120k miles.

Our 4WD 2017 has the HD tow package (RPO code: NHT)... my understanding is the 6L80 tansmission is actually a different part number than the standard 6L80. I'm not sure the difference, but seems to me it's the cooling fluid is routed different in the HD-variant vs. the standard(?)... but my question is this:

***Does it matter to be certain that the replaced transmission is the "HD" version? I personally can't figure out a way to verify myself what part#/version was replaced with.

[if consensus is it's a non-consequentional difference, then I won't bother; If it's a consequential difference, then how can a layman tell the difference in physical parts?]

The NHT does have a different part number for a complete transmission as does the torque converter.

Regular 6L80 - 19431764

NHT 6L80 - 19437166

Torque Converter - 19419376 for NHT

TC New - 24247371 or TC Used - 19419378

 

[NickTransmissions]

just had the 6L80 replaced with a rebuilt.... 120k miles.

Our 4WD 2017 has the HD tow package (RPO code: NHT)... my understanding is the 6L80 tansmission is actually a different part number than the standard 6L80. I'm not sure the difference, but seems to me it's the cooling fluid is routed different in the HD-variant vs. the standard(?)... but my question is this:

***Does it matter to be certain that the replaced transmission is the "HD" version? I personally can't figure out a way to verify myself what part#/version was replaced with.

[if consensus is it's a non-consequentional difference, then I won't bother; If it's a consequential difference, then how can a layman tell the difference in physical parts?]

AFAIK, the only true HD version of the 6L80 transmission is the 6L90 transmission...Beyond that, the K2 chassis vehicles had a thermal bypass valve (which was anything but an upgrade). If GM put out a HD RPO for the 6L80, the RPO code would be different than the 6L80's RPO which is "MYC" (the 6L90 is "MYD")...

Referring to @swathdiver's post above, GMparts.com's listing for the 19437166 does make reference to a heavy duty towing package which implies the transmission has components that are either higher strength or can handle more torque/power/stresses than the non-NHT 6L80s. If that is the case, my guess is that the front planet is the six-pinion design ported over from the 6L90s and the 3-5-R clutch pack has one additional friction and steel (possible w/a lower profile 3-5-R apply ring like the Sonnax 35R Hi-Cap apply ring). The 4-5-6 clutch may also have an addl friction and steel but that would require programming, specifically tuning out the air bleed in the 456 clutch pack unless the GM unit somehow keeps the waved cushion plate (perhaps w/a thinner set of frictions and steels) in that clutch pack (the Sonnax kit deletes it).

But those are just guesses as I've never come across one of these NHT units before (or if I have, I didn't realize it at the time).

I did a quick G-search to see if anything definitive came up and found this thread where one of the members states the NHT option had nothing to do w/the transmission itself but the transmission cooler, which apparently is different on those NHT RPO trucks vs the non-NHT vehicles.

Check your glove box or where ever the RPO codes are available in your Tahoe and see if you have a different transmission RPO than the 'standard' 6L80's MYC. If so, that would indicate a substantially different transmission compared to the 6L80 we're all familiar with.

 

[swathdiver]

AFAIK, the only true HD version of the 6L80 transmission is the 6L90 transmission...

I built a 2017 GMC Yukon over at GMPartsGiant and found those numbers. Also perused through all the internal parts looking for NHT specific items and didn't see any, it was a quick look. Cases are the same too.

I'm speculating that the difference is in the programming.

 

[NickTransmissions]

I built a 2017 GMC Yukon over at GMPartsGiant and found those numbers. Also perused through all the internal parts looking for NHT specific items and didn't see any, it was a quick look. Cases are the same too.

I'm speculating that the difference is in the programming.

Yea def could be...Ive torn down a lot of 6L80s across all years and never seen any (yet) with factory upgrades beyond what enginnering changes to existing parts over the years to address common failures. Occasionally ill see some Sonnax stuff but nothing like the six-speed equivalent to the 4L65E (ie a "6L85") from the OEM

 

[ers37]

AFAIK, the only true HD version of the 6L80 transmission is the 6L90 transmission...Beyond that, the K2 chassis vehicles had a thermal bypass valve (which was anything but an upgrade). If GM put out a HD RPO for the 6L80, the RPO code would be different than the 6L80's RPO which is "MYC" (the 6L90 is "MYD")...

Referring to @swathdiver's post above, GMparts.com's listing for the 19437166 does make reference to a heavy duty towing package which implies the transmission has components that are either higher strength or can handle more torque/power/stresses than the non-NHT 6L80s. If that is the case, my guess is that the front planet is the six-pinion design ported over from the 6L90s and the 3-5-R clutch pack has one additional friction and steel (possible w/a lower profile 3-5-R apply ring like the Sonnax 35R Hi-Cap apply ring). The 4-5-6 clutch may also have an addl friction and steel but that would require programming, specifically tuning out the air bleed in the 456 clutch pack unless the GM unit somehow keeps the waved cushion plate (perhaps w/a thinner set of frictions and steels) in that clutch pack (the Sonnax kit deletes it).

But those are just guesses as I've never come across one of these NHT units before (or if I have, I didn't realize it at the time).

I did a quick G-search to see if anything definitive came up and found this thread where one of the members states the NHT option had nothing to do w/the transmission itself but the transmission cooler, which apparently is different on those NHT RPO trucks vs the non-NHT vehicles.

Check your glove box or where ever the RPO codes are available in your Tahoe and see if you have a different transmission RPO than the 'standard' 6L80's MYC. If so, that would indicate a substantially different transmission compared to the 6L80 we're all familiar with.

Yes, I can confirm there is the "MYC" code as well. Thank you all for the info. I've been [as a novice] looking into this too and without certainty, I think these may be the difference:
--- additional ball/check valves for trans fluid
--- larger trans radiator/cooler
--- upgraded (or additional) friction pad(s) clutch
--- slightly different torque converter (I've seen small differences in dimensional measurements between the TCs online; also reference to "reinforced" for the HD one)
--- and software, incl. less gear shifting/searching programmed in.

all-in-all leads me to not be concerned to be certain the rebuild was an "HD" option.

 

[NickTransmissions]

Yes, I can confirm there is the "MYC" code as well. Thank you all for the info. I've been [as a novice] looking into this too and without certainty, I think these may be the difference:
--- additional ball/check valves for trans fluid
--- larger trans radiator/cooler
--- upgraded (or additional) friction pad(s) clutch
--- slightly different torque converter (I've seen small differences in dimensional measurements between the TCs online; also reference to "reinforced" for the HD one)
--- and software, incl. less gear shifting/searching programmed in.

all-in-all leads me to not be concerned to be certain the rebuild was an "HD" option.

No additional check balls beyond the 8 check balls in the valve body starting in 2014+ (that 8th check ball can be retro'ed to any VB back to 2010 w/the third design spacer plate). No additional frictions or steels, either, unless you add them via aftermarket hi-cap kits. The 6L90s had an additional friction and steel in every clutch pack in the HD/HP units.

Also the JMBX torque converter is the same for the 6L80s and 90s except for the 90's TCs have a flanged hub - this applies to the trucks...The Camaro ZL1, CTS-V and other performance vehicles have a completely different torque converter.

Software and radiator/trans cooler is believe is where the main upgrades for that package lie as it relates to the transmission...

 

[ers37]

No additional check balls beyond the 8 check balls in the valve body starting in 2014+ (that 8th check ball can be retro'ed to any VB back to 2010 w/the third design spacer plate). No additional frictions or steels, either, unless you add them via aftermarket hi-cap kits. The 6L90s had an additional friction and steel in every clutch pack in the HD/HP units.

Also the JMBX torque converter is the same for the 6L80s and 90s except for the 90's TCs have a flanged hub - this applies to the trucks...The Camaro ZL1, CTS-V and other performance vehicles have a completely different torque converter.

Software and radiator/trans cooler is believe is where the main upgrades for that package lie as it relates to the transmission...

Nick, thank you for all the knowledge! question feels resolved to me.

... now on to figuring out the best way to prevent/delay the notorious lifter failure that'll kill the cam/engine. (had this happen to an earlier Tahoe at ~170k miles and I don't want to go through that again...)

 

[NickTransmissions]

Nick, thank you for all the knowledge! question feels resolved to me.

... now on to figuring out the best way to prevent/delay the notorious lifter failure that'll kill the cam/engine. (had this happen to an earlier Tahoe at ~170k miles and I don't want to go through that again...)

You're welcome, man!