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Discussion Starter · #1 ·
I really don't want to tune my duramax right now but it looks like I need to tune it inorder to tune the transmission. The upshift points when just DD are starting to get annoying and the amount of TC non locking when towing is obnoxious and I have only done about 300 miles of towing. So are there any options to just tune the transmission?
 

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FYI: 5th and 6th gears in the 6 speed are overdrives, just drop it to 4th or 5th and go on down the road. Motor will probably like it too

4th is 1:16 to 1
5th is 0:85 to 1
6th is 0:71 to 1
 
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Discussion Starter · #3 ·
FYI: 5th and 6th gears in the 6 speed are overdrives, just drop it to 4th or 5th and go on down the road. Motor will probably like it too

4th is 1:16 to 1
5th is 0:85 to 1
6th is 0:71 to 1
Why on early would I roll around at like 2000rpm in 4th? Thats exactly what is annoying about DDing? Also if i wanted to just run in a lower gear I would just keep it in tow/haul mode. But that isn't what i want
 

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FYI: 5th and 6th gears in the 6 speed are overdrives, just drop it to 4th or 5th and go on down the road. Motor will probably like it too

4th is 1:16 to 1
5th is 0:85 to 1
6th is 0:71 to 1
That's not what they were talking about. The stock trans tune upshifts way too late, IMO, and the TCC lock also happens too late at times, all in the name of "driveability." It's not an issue that manually keeping the trans in lower gears solves because it's the opposite problem, assuming the OP is feeling the same way I do about the OEM trans tune.

The GDE trans tune makes my truck shift more like the 68RFE behind my Cummins did, almost short-shifting to keep the engine at peak torque in lower gears instead of winding the engine out. Also locks the TCC early on.

The problem I have with the GDE trans tune is actually with towing, the 1-2 upshift really bangs into gear.
 
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You'll need a unlocked TCM and HP Tuner. $600-880 for everything.
 
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Discussion Starter · #7 ·
That's not what they were talking about. The stock trans tune upshifts way too late, IMO, and the TCC lock also happens too late at times, all in the name of "driveability." It's not an issue that manually keeping the trans in lower gears solves because it's the opposite problem, assuming the OP is feeling the same way I do about the OEM trans tune.

The GDE trans tune makes my truck shift more like the 68RFE behind my Cummins did, almost short-shifting to keep the engine at peak torque in lower gears instead of winding the engine out. Also locks the TCC early on.

The problem I have with the GDE trans tune is actually with towing, the 1-2 upshift really bangs into gear.
**** i didn't me to double post but i forgot to reply. this is exactly it. I feel like when i daily drive it refuses to upshift and not only is it kind of annoying to drive, it is just wasting fuel. And the 2nd issue is what you said about towing. I have only done 3 trips of about 100 miles with my brz but i feel like the TC is almost never locked even in tow/haul. I haven't driven't a vehicle with a TC in well over a decade so maybe i just hate TCs. Too bad they didn't offer a manual :(
 

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Why on early would I roll around at like 2000rpm in 4th? Thats exactly what is annoying about DDing? Also if i wanted to just run in a lower gear I would just keep it in tow/haul mode. But that isn't what i want
I guess I should have asked what you daily driving consist of, my bad

Mine is 1.2 mile to the interstate and then 1/4 mile off the interstate unless I am going fishing that day
 

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That's not what they were talking about. The stock trans tune upshifts way too late, IMO, and the TCC lock also happens too late at times, all in the name of "driveability." It's not an issue that manually keeping the trans in lower gears solves because it's the opposite problem, assuming the OP is feeling the same way I do about the OEM trans tune.

The GDE trans tune makes my truck shift more like the 68RFE behind my Cummins did, almost short-shifting to keep the engine at peak torque in lower gears instead of winding the engine out. Also locks the TCC early on. The problem I have with the GDE trans tune is actually with towing, the 1-2 upshift really bangs into gear.
Interesting. I am running GDE's "09AC" settings, which came with their compliant tune, and the 1-2 shift is a bit soft, slipping for a couple of seconds, while all the other shifts are quick, with a perfect blend firmness and smoothness. Earlier GDE settings I used were a bit harsher, but were still greatly preferable to the stock mushy and late shifting mess, in my truck's case, the stock 3-4 shift was particularly awful - I called it the "dipsy doodle shift" as it would slip, kind of engage, then slip, then finally engage. It was not shudder, just incredibly lazy.

With the exception of the 1-2 shift being a bit soft, the GDE settings seem to be as good as they could possibly be with our transmission. I just sort of ease off the line, and once it is locked out in 2nd gear, I can roll in the beans and go if I want to, punting forward nicely through the gears with it shifting at 2K RPM. This is not a big deal, as I am not a jackrabbit off the line driver anyway. I talked to GDE about this awhile ago, these transmissions all vary. I guess it was Keith I spoke to, he wishes that our trucks got the 8 speed like the vans with the 2.8 do.

Speaking of 8 speeds, after driving a rented RAM pickup with a 5.7 and it's marvelous quick and smooth shifting ZF 8 speed, and riding on my buddy's scary fast Mustang GT with it's ridiculous 5.0 V8 and incredible 10 speed rapid firing shifts in track mode like a machine gun, I can only conclude our 6L50 transmissions are so far behind the times as to be a bit laughable at this point. Can't complain though, the old 6 speed continues to serve well, have not had any abnorbal behavior, it is a smooth transmission, it is just not "sophisticated" like the new stuff. That ZF 8 speed in the RAM would be so sweet with our 2.8.
 

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Discussion Starter · #10 ·
I guess I should have asked what you daily driving consist of, my bad

Mine is 1.2 mile to the interstate and then 1/4 mile off the interstate unless I am going fishing that day
I actually wfh so its more running errands or going on trips. Like today i ran out for lunch and it was like 15 minutes of the engine roaring on a 40mph road which got real old real quick. When i took it on a 1000+ mile round trip I set cruise control at 75mph and just steered it was pretty alright.
 

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Interesting. I am running GDE's "09AC" settings, which came with their compliant tune, and the 1-2 shift is a bit soft, slipping for a couple of seconds, while all the other shifts are quick, with a perfect blend firmness and smoothness. Earlier GDE settings I used were a bit harsher, but were still greatly preferable to the stock mushy and late shifting mess, in my truck's case, the stock 3-4 shift was particularly awful - I called it the "dipsy doodle shift" as it would slip, kind of engage, then slip, then finally engage. It was not shudder, just incredibly lazy.

With the exception of the 1-2 shift being a bit soft, the GDE settings seem to be as good as they could possibly be with our transmission. I just sort of ease off the line, and once it is locked out in 2nd gear, I can roll in the beans and go if I want to, punting forward nicely through the gears with it shifting at 2K RPM. This is not a big deal, as I am not a jackrabbit off the line driver anyway. I talked to GDE about this awhile ago, these transmissions all vary. I guess it was Keith I spoke to, he wishes that our trucks got the 8 speed like the vans with the 2.8 do.

Speaking of 8 speeds, after driving a rented RAM pickup with a 5.7 and it's marvelous quick and smooth shifting ZF 8 speed, and riding on my buddy's scary fast Mustang GT with it's ridiculous 5.0 V8 and incredible 10 speed rapid firing shifts in track mode like a machine gun, I can only conclude our 6L50 transmissions are so far behind the times as to be a bit laughable at this point. Can't complain though, the old 6 speed continues to serve well, have not had any abnorbal behavior, it is a smooth transmission, it is just not "sophisticated" like the new stuff. That ZF 8 speed in the RAM would be so sweet with our 2.8.
How would I find which settings I'm using? My 1-2 upshift is fine when not towing, just when towing 4,000-5,000LB the 1-2 upshift off the line is really hard and I feel like over time something may break.
 

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How would I find which settings I'm using? My 1-2 upshift is fine when not towing, just when towing 4,000-5,000LB the 1-2 upshift off the line is really hard and I feel like over time something may break.
You could hook up your Autocal and read the tune off the TCM, then we could see what the tune file name is and tell how old it is.

I could not tell any difference between the "08AC" file and the "09" that comes with the compliant settings. As an existing customer, for $50 GDE will sell you the compliant settings, you can run their latest trans tune that way. Currently running their last pre crackdown "intact" engine tune with the trans tune from the complaint tune package.
 

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You could hook up your Autocal and read the tune off the TCM, then we could see what the tune file name is and tell how old it is.

I could not tell any difference between the "08AC" file and the "09" that comes with the compliant settings. As an existing customer, for $50 GDE will sell you the compliant settings, you can run their latest trans tune that way. Currently running their last pre crackdown "intact" engine tune with the trans tune from the complaint tune package.
I bought my tunes from GDE back in Feb so they were only selling the compliant tunes. I've emailed them to see if there's an updated trans tune that might help with this 1-2 upshift concern.

Sent from my SM-G986U using Tapatalk
 
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Interesting. It appears we are both using the same transmission tune file, but our respective transmissions behave quite differently. The "your mileage may vary" saying is true it seems. This probably explains the sloppy OEM settings - no change of a hard shift there, regardless of an individual transmission's tolerances.
 

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Interesting. It appears we are both using the same transmission tune file, but our respective transmissions behave quite differently. The "your mileage may vary" saying is true it seems. This probably explains the sloppy OEM settings - no change of a hard shift there, regardless of an individual transmission's tolerances.
I got an initial reply and this is the first they've heard of such a complaint, they also say the TCC is unlocked for the 1-2 upshift, so that being the case it's the TCC lockup, not the 1-2 upshift, that is harsh. It's the second RPM drop that happens roughly a second after the first RPM drop, I assumed the first drop was the TCC considering it was the softer of the two and resulted in less RPM drop than the second. I can load my truck up to (or a little over) GVWR and drive all day long without this happening, but hook up the horse trailer (~3,500LB empty) or boat (~4,500LB) and it happens every time when starting from a stop with normal throttle at about 25-35MPH when it does the 1-2 upshift and TCC lock. First RPM drop (apparently 1-2 upshift) is fine, second (very shortly after the first) is like it's just dumping the clutch on a manual trans since, I guess, the TCC lockup is happening very quickly.
 

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I bought my tunes from GDE back in Feb so they were only selling the compliant tunes. I've emailed them to see if there's an updated trans tune that might help with this 1-2 upshift concern.

Sent from my SM-G986U using Tapatalk
they were really good in the pre-clamp down days about rolling out updates due to feedback.
im not sure if that will carry on now if each variant needs to be recertified (maybe it doesnt...?)
 

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they were really good in the pre-clamp down days about rolling out updates due to feedback.
im not sure if that will carry on now if each variant needs to be recertified (maybe it doesnt...?)
I've already discussed that with them previously, after I noticed automatic grade braking was enabled in L mode, which my stock trans tune doesn't do and the owner's manual confirms it's disabled, I reached out about having it disabled and I was told that's the way the factory tune is (false) and that changing that would require recertification at a cost of like $12k. So, I've been fighting with the dilemma of keeping the GDE trans tune installed because overall it's better than stock, or putting the stock trans tune back to fix the harsh lockup when towing and to get downshift control back when in L mode.
 

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With the GDE compliant trans file I have not noticed grade braking activated in L mode unless Tow/Haul is turned on, then it is insane. Have not really focused on it though, but have been on many trips through the mountains. Hmm. Will have to check that out further.
 

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With the GDE compliant trans file I have not noticed grade braking activated in L mode unless Tow/Haul is turned on, then it is insane. Have not really focused on it though, but have been on many trips through the mountains. Hmm. Will have to check that out further.
Yeah, the whole point of L + Tow/Haul is to get the EB working at reasonable RPMs without the transmission downshifting and sending the RPMs to the moon. I'd used that mode countless times when stock so to lose that with the GDE trans tune was really disappointing.
 
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Just wanted to circle back on my experience with the GDE trans tune and GDE after taking some time to do some additional tow tests. My memory was fuzzy about which shift/RPM drop was the problem, turns out it was the 1-2 upshift and not TCC lock as it was the first RPM drop, not the second.

So, I went to the barn today and hitched up the horse trailer to test D, L, and T/H modes. Here's what I experienced and what I've passed on to GDE.
  • D, T/H disabled, trailer hitched up, starting from a stop with like 30-50% throttle there's a thud/bump as it upshifts from 1-2. TCC lockup is fine.
  • D, T/H enabled, trailer hitched up, starting from a stop with the same throttle input the thud/bump is much less pronounced and I don't see it as an issue. The difference here is that with T/H enabled the transmission isn't short-shifting for the 1-2 upshift and is holding 1st gear longer. The 1-2 upshift is firm but not harsh. The grade braking will downshift to the moon with minimal brake input even on flat ground.
  • L, T/H enabled, trailer hitched up, slowing from 55 to a stop it doesn't trigger grade braking on flat ground like in D. Apparently it only goes into rage mode in L with T/H when there are actual hills and it thinks it needs to downshift because the truck isn't slowing fast enough?
Anyway, GDE is going to try and reproduce the harsh 1-2 upshift while towing but without T/H enabled. Even if there's no fix, I can at least work around the issue by changing trans or T/H settings to run where it and I are both generally happy. Going back to the stock trans tune is a last resort, and the main test is going to see what our off-road trailer tows like once it arrives next year. It's much lighter than the other trailers I tow/have towed and I'll do whatever needs to be done to make sure the truck is happy towing it as we're planning on putting a lot of miles behind us with it.
 
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