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I do this every time I come/go anywhere. I'm not in high gears though (never really tried it on the highway). When I crest the hill at the top of the canyon, I hit the EB, wait for it to upshift to 4th due to the lack of throttle, then drop it into L (3rd gear). I just hold it there all the way down, tapping the brakes as necessary on warmer days to keep it within 5mph of the 35mph speed limit. Does not down shift unless I tell it, which I don't because I don't want it to rev to the moon.

If I have cruise on, it'll downshift to the moon once it gets to some mph over the set point. If I have EB and cruise on, it'll shift to the moon with a lower threshold over the cruise set point. It WILL down shift if I'm going very slowly (like when I pull into the driveway), but not for braking purposes that I've experienced.

I wonder if there's a difference in GM's trans tune from year to year?
 

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@Duken4evr , thanks for the impressions .. curious about your long term impressions re. EGR residue etc once you have some more miles on this tune.

@GreenDiesel , does the latest tune hobble the truck when codes are thrown .eg. my truck which is on an older GDE tune currently has a NOX sensor code .. I just clear it and go about my business without worrying about any "xx miles till speed limited " messages .
 

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Discussion Starter · #65 ·
@GreenDiesel , does the latest tune hobble the truck when codes are thrown .eg. my truck which is on an older GDE tune currently has a NOX sensor code .. I just clear it and go about my business without worrying about any "xx miles till speed limited " messages .
Now that alone might be reason enough to buy the tune! One of my biggest fears is getting stranded 2 states from home with a truck full of toys and my family (or in the 3rd world country called Miami while passing through with my boat) due to some emissions problem. If the GDE tune would allow you to just clear the code and continue indefinitely, and fix the problem when it's convenient for me, then that's worth the price of admission by itself!
 

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Now that alone might be reason enough to buy the tune! One of my biggest fears is getting stranded 2 states from home with a truck full of toys and my family (or in the 3rd world country called Miami while passing through with my boat) due to some emissions problem. If the GDE tune would allow you to just clear the code and continue indefinitely, and fix the problem when it's convenient for me, then that's worth the price of admission by itself!
Yep
Esp. when not even on the roads.

Happened to me on the beach with 2 kids and 2 other adults and a bed full of camping gear . I just cleared the code and carried on. I'd be curious about the current behavior.

Likewise with a DEF heater code in the middle of our famous texas electric outage :)
 

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@Duken4evr , thanks for the impressions .. curious about your long term impressions re. EGR residue etc once you have some more miles on this tune.

@GreenDiesel , does the latest tune hobble the truck when codes are thrown .eg. my truck which is on an older GDE tune currently has a NOX sensor code .. I just clear it and go about my business without worrying about any "xx miles till speed limited " messages .
It depends on the fault code as far when limp mode is active. Part of being emission compliant is meeting the OBD requirements, DEF messages need to be fixed in a timely manner.
 

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Discussion Starter · #68 ·
One more data point; going by this post there is a specific 6L50 transmission for the 2.8 diesel that is rated 550Nm, or about 406 ft lb. The GDE web site shows their tune bumps the engine to 403 fb lb torque, so that's more or less right at the max rating for the transmission, but most importantly not significantly over the rated torque. Assuming the post about the specific transmission for the 2.8 is accurate, that alleviates the concern about twisting the transmission harder than it was designed for.
 

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So i have a question for green diesel. I am considering getting your tune in about a year when my extended warranty is over. My main concern is blowing a head gasket sooner with the extra power. Are your cylinder pressures lower across the rpm band with your tune. I am more interested in the drivability of it and lower egr levels.
 

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One more data point; going by this post there is a specific 6L50 transmission for the 2.8 diesel that is rated 550Nm, or about 406 ft lb. The GDE web site shows their tune bumps the engine to 403 fb lb torque, so that's more or less right at the max rating for the transmission, but most importantly not significantly over the rated torque. Assuming the post about the specific transmission for the 2.8 is accurate, that alleviates the concern about twisting the transmission harder than it was designed for.
Rather certain GDE's results are from the chassis dyno, not an engine dyno. Based on their stock vs tuned numbers, the stock HP number is ~10% less than published power at the crank, torque is ~5% less. So 406lb-ft + 5% = 426lb-ft at the crank. Similarly, 202HP at the wheels + 10% = 222HP at the crank. Rough estimate just based on GM's crank numbers vs GDE's stock numbers from a chassis dyno.
 
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Rather certain GDE's results are from the chassis dyno, not an engine dyno. Based on their stock vs tuned numbers, the stock HP number is ~10% less than published power at the crank, torque is ~5% less. So 406lb-ft + 5% = 426lb-ft at the crank. Similarly, 202HP at the wheels + 10% = 222HP at the crank. Rough estimate just based on GM's crank numbers vs GDE's stock numbers from a chassis dyno.
I seem to remember discussions on tuner sites that dyno numbers where best left as relative numbers of before and after tunes using the same dyno. Comparing results between different Dyno manufacturers resulted in differences that would lead to much debate. What dynos did GDE and GM use?
 

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I seem to remember discussions on tuner sites that dyno numbers where best left as relative numbers of before and after tunes using the same dyno. Comparing results between different Dyno manufacturers resulted in differences that would lead to much debate. What dynos did GDE and GM use?
Manufacturer-published numbers are from an engine dyno, GDE from a chassis dyno (IIRC for GDE), as I mentioned. GDE's results with stock vs tuned is on the same dyno so they can be compared, what I'm saying is that if we use 181HP and 369lb-ft as factory numbers at the crank from the engine dyno then GDE's stock numbers from the chassis dyno give a rough estimate of drivetrain losses at similar RPMs and factoring those losses into GDE's chassis dyno numbers gives an approximation of what the numbers are at the crank. GDE's numbers are not at the crank and as such are not what the transmission or torque converter are seeing, what they see is higher.
 

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Manufacturer-published numbers are from an engine dyno, GDE from a chassis dyno (IIRC for GDE), as I mentioned. GDE's results with stock vs tuned is on the same dyno so they can be compared, what I'm saying is that if we use 181HP and 369lb-ft as factory numbers at the crank from the engine dyno then GDE's stock numbers from the chassis dyno give a rough estimate of drivetrain losses at similar RPMs and factoring those losses into GDE's chassis dyno numbers gives an approximation of what the numbers are at the crank. GDE's numbers are not at the crank and as such are not what the transmission or torque converter are seeing, what they see is higher.
I think I got the gist of you original post. I wasn't trying to mix types of dynos but rather dyno manufacturers. Hypothetically an air filter manufacturer makes a claim that the filter they are selling will add HP. They test the original vehicle with a chassis dyno from manufacturer A that is known to read lower HP and then add their filter and use a chassis dyno from manufacturer B that is known to read higher. They haven't lied per say but they aren't truthful either. Both dynos are valid but from what I understand they calculate HP slightly different.

I want to emphasis I am not implying GDE or any tuner on this site does that. All I am suggesting is that results before and after on the same dyno is best. Cross comparisons using different dyno types and manufacturers less so, including when drivetrain losses need to be estimated.

Have you considered weighing the truck and using one of those acceleration apps. You could back calculate the losses to the input shaft and negate the TC slippage. Tow the truck in neutral at varying speeds with a strain gauge and to get the rolling resistance and air drag. But then again drivetrain losses under load would have to be estimated. But you could then set an alarm if you exceed a torque level. Just a thought.
 

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GDE mentioned on p2 using the above system. The splash graphic shows an engine dyno, but the specific device is mounted in the vehicle, which points further to chassis dyno.
 

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I think I got the gist of you original post. I wasn't trying to mix types of dynos but rather dyno manufacturers. Hypothetically an air filter manufacturer makes a claim that the filter they are selling will add HP. They test the original vehicle with a chassis dyno from manufacturer A that is known to read lower HP and then add their filter and use a chassis dyno from manufacturer B that is known to read higher. They haven't lied per say but they aren't truthful either. Both dynos are valid but from what I understand they calculate HP slightly different.

I want to emphasis I am not implying GDE or any tuner on this site does that. All I am suggesting is that results before and after on the same dyno is best. Cross comparisons using different dyno types and manufacturers less so, including when drivetrain losses need to be estimated.
Yes, well aware of this and why the numbers are all estimates. GDE never claimed to be comparing their dyno results to GM's numbers, I was simply providing rough estimates on output at the crank in the context of what the transmission may be seeing. The chance of there being 0% drivetrain loss is 0%. The numbers I used based on GM's and GDE's numbers are actually on the low end of what "typical" drivetrain losses are (It's been a while, but I think 12-18% loss was the typical range across various vehicles). Could our drivetrain see higher losses than what I estimated? Sure. I doubt it would be much higher, though, but all I have to go on for crank output is the info from GM vs GDE's stock dyno numbers. SAE net ratings from manufacturers include all exhaust components and engine-mounted and -driven accessories (alt, water pump, A/C compressor, etc) and it's been that way since roughly 1972. Meaning the chance our engines deviate much from GM's published numbers is pretty low. Based on that assumption, we can get a reasonable idea of what drivetrain losses are to compare crank output, which ultimately isn't what matters when it comes to performance. The numbers were simply to say that the GDE tune likely exceeds the input shaft rating of the 6L50 when putting out peak torque.

Have you considered weighing the truck and using one of those acceleration apps. You could back calculate the losses to the input shaft and negate the TC slippage. Tow the truck in neutral at varying speeds with a strain gauge and to get the rolling resistance and air drag. But then again drivetrain losses under load would have to be estimated. But you could then set an alarm if you exceed a torque level. Just a thought.
I don't care enough to do anything of the sort.
 

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@GreenDiesel Great info, thank you very much! Final question; relative the OEM tune, do you run higher fuel rail pressures for the same power output?
I didn't see an answer to this. Did you get this along the way somewhere? My concern is that I have the dreaded HPFP ticking going on and I do have the @GreenDiesel tune installed and was wondering if I need to worry or not.
 

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I guess ignorance is indeed bliss. I've been running for about 30k miles with the ticking, and that was before I installed the tune. I hope that is all it does it tick and I don't have to put up $4k for that repair bill.
 

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I guess ignorance is indeed bliss. I've been running for about 30k miles with the ticking, and that was before I installed the tune. I hope that is all it does it tick and I don't have to put up $4k for that repair bill.
Looking at one of the newest diesel supeliments for the 2.8l they (GM) now recomend running fuel additives for non top tier diesel (almost every diesel fuel sold in the US right now). My 2016 they said it was not needed.:rolleyes:
 
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