Diablew Tune Review - 2014 Sierra 5.3L

[Bill Reinhardt]

Truck details

• Make/Model: GMC Sierra
• Year: 2014
• Engine: 5.3L L83
• Trim: Work truck (blue blood truck right here)
• Transmission: 6-speed w/ 4 wheel drive
• Gears: 3.42
• Miles on truck: ~53k
• Miles driven on tune: ~3k
• Performance Mods: None, apart from the tune of course
• Other mods: bed cover, remote start, tailgate damper
• Tuner: Diablo Intune I2
• Truck role: Getting to/from work and doing work. Have another car for long trips

 

Background

 

I purchased a Diablosport Intune I2 for my previous vehicle, 08 Colorado I5. The tuner for that truck was the best investment I ever made, especially for the transmission tune. Lightning-quick shifts, more power, better throttle response, no complaints. That truck has since left my life, needed something with more payload, in comes the Sierra...

 

Intro

 

The truck commutes 15 miles per day for work and is otherwise a weekend warrior. About 80% city, 20% highway driving. Had no complaints with how the truck drove, until I started noticing an occasional downshift "clunk" when going around corners between 20-30 mph. Then, I remembered how awesome the I2 made my Colorado transmission. Said, "Screw it, lets tune this thing and see if the problem goes away." So I purchase the extra license for my i2, install the canned 87 octane/firm shift tunes, and go out for a drive... Big mistake. The canned transmission tune was QUITE bad. Started investigating, lots of complaints on the Diablosport forums, only solution is to try a Diablew tune. So, $150 and 3k miles later, here we are!

 

The Process

 

Contact Diablew with your information, wait 5 seconds for him to respond, pay the man, follow the instructions, profit (for him... and you, eventually). Don't want to cover this too much as it's not that interesting. Onto the tune!

 

The Tune

 

One engine and one transmission tune provided with tweaks available upon request. The engine tune can be provided for the octane of your choice, but keep in mind that the 87 and 89 octane tunes are the same with no spark advance provided for 89 (ie. might as well run 87 unless you tow in high temps, or just request the 91+ tune).

 

The engine tune, after driving 150-ish miles... wow, I like it. Noticeable power increase in the low end (around 1.5k rpms). Feels better across the board. On the stock tune, I was getting random blips of knock retard on mobil gas, even 89 octane. The Diablew engine tune has yet to register ANY knock retard on 87 mobil. Better for the engine, more power, can't complain. The V4 mode was also disabled, though I did not have an issue with V4 (part of the "Cannot notice it's even working" club, which only has 7 or so members on this forum). MPGs are about the same, pedal feel is spot-on, spins the tires too easily (not a complaint, unless its raining)

 

The transmission tune, on the other hand... it's not bad, but not for me. This was the primary reason why I wanted to tune in the first place, but I am a bit disappointed as a transmission tune made my Colorado (by comparison) FAR better than stock. The tuned transmission on this truck shifts a tad later (which I felt wasn't necessary) and also *tries* to shift firmer. I say "tries" because the firmness is random. When the transmission tune shifts firmly across all gears, I love it. But, the inconsistency breaks it for me. It also does NOT shift faster than stock, or at least not noticeably so. After searching through tune forum posts for this truck, it seems like everyone has had a different experience and probably no fault to Lew as a tuner, just that the truck has a silly transmission. No improvements after 3k miles of driving on this transmission tune, either. Remember that downshift clunk when taking turns around 20-30 mph? Since the transmission now shifts harder, the flaws are more pronounced. I reverted back to stock and due to the additional engine power in the low end, I think it makes the stock tune that much better. Due to the higher shift points, I feel that this tune would make more sense for a truck with the 3.08 gears (vs. my 3.42) as many people with 3.08's seem to hate the shift points. The tune is worth a shot no matter what, but my truck did not like it, unfortunately.

I gave the Diablew TCM tune another shot. After the paint-stick-gas-pedal mod, this tune has definitely improved. Lew says its the adaptive transmission just doing its thing (more the reason to shove something up behind that gas pedal, the truck just performs better all around). The upshifts are much better, driveability all around is "as it should be" and the shift speed is definitely better than stock. Shifts fast and smooth. The only complaint I had was with the downshifting. When approaching a stoplight, the truck felt like it had a less-aggressive engine brake, causing me and my passengers to lunge forward. After asking Lew to modify the downshifts to be less-aggressive, I loaded the new TCM tune and all is well. I have changed my review to reflect that the TCM tune takes some time to adjust, but combined with the gas pedal mod, its totally worth it. Just be wary of how your truck behaves on the downshifts and notify Lew accordingly.

 

Final thoughts

 

Want more power for only a few hundred clams? Get a Diablewtune. More power than the canned tunes, less knock retard, and will take advantage of engine mods. Certainly try the transmission tune as "your mileage may vary" (har har), but the engine tune alone was worth it. Estimated gains from Lew are 12-39 HP, 10-35 lb-ft of torque, and +0-3 mpgs (all of which are mod dependent). Since I have no mods, I am happy with an additional 12HP/10lb-ft.

 

Feel free to ask any questions!

[catpartsman]

Thanks for this write up! I’ve been researching tunes for my truck and since I just ordered an Airaid JR kit I’m gonna order a time very soon. I’ve been looking at the diablo intune and SCT but leaning toward the Diablo. Since this write up I’m gonna do the diablo with the diablew tune. This is just what I was looking for!


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[Bill Reinhardt]

On 6/20/2018 at 10:26 PM, catpartsman said:

Thanks for this write up! I’ve been researching tunes for my truck and since I just ordered an Airaid JR kit I’m gonna order a time very soon. I’ve been looking at the diablo intune and SCT but leaning toward the Diablo. Since this write up I’m gonna do the diablo with the diablew tune. This is just what I was looking for!
 

I appreciate the feedback! Yea, just make Lew aware of your mods and he will adjust the tune to take full advantage of them.

 

I should also add that I just did the paint stick gas pedal mod (link) yesterday. Wow, holy crap, that forum post is not wrong. Made the tune feel much better and more responsive. I had to use 2 paint sticks, though (broke one in half, shoved it up underneath the plastic).

[SWOYER]

I like my diablew tune also, really smoothed out the stock trans clunk and such. Truck is much peppier on the 93 tune. 

[Bill Reinhardt]

On 6/24/2018 at 5:07 PM, SWOYER said:

I like my diablew tune also, really smoothed out the stock trans clunk and such. Truck is much peppier on the 93 tune. 

Curious as to what engine and rear axle you have

[Bill Reinhardt]

Updated my review to reflect new developments with the TCM tune. Much improved after the stupid but necessary paint stick gas pedal mod. Also had Lew adjust for downshift feel. Clunk is still present, but it seems to be more of a driveline slack problem than a transmission problem.

[catpartsman]

Ok. Maybe I’m missing something regarding the gas pedal flex. I have zero flex issues with my pedal. Everything seems to be mounted solid and I am not sure where I would even put the paint stick. Can someone tell me if I’m missing something here?


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[Yondu]

38 minutes ago, catpartsman said:

Ok. Maybe I’m missing something regarding the gas pedal flex. I have zero flex issues with my pedal. Everything seems to be mounted solid and I am not sure where I would even put the paint stick. Can someone tell me if I’m missing something here?


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Yours looks different than mine perhaps you have adjustable pedals? Mine are fixed. Before I put a shim behind the mount on the bottom I could push the gas pedal down with my hand and see the mount flexing before the gas pedal itself moved. I've heard some say the adjustable pedals have no flex other say they have less flex but I've never seen them in person.

[catpartsman]

Yes my pedals are adjustable. I’m guessing that’s the difference in the lack of flex. Thanks for the reply!


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[midwestdenaliguy]

1 hour ago, catpartsman said:

Yes my pedals are adjustable. I’m guessing that’s the difference in the lack of flex. Thanks for the reply!


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I looked at mine too and they put in a different bracket in the 2016+ trucks, I have a 2016 Sierra. Also, yours is adjustable (like mine) and I have zero movement in mine. Most 2016+/adjustable pedal guys don't have the flex like the 2014/2015 pedals. Some claimed they did and put in the shim, but it seems to be rare. If you watch a video on a 2014/2015 pedal bracket moving it's very obvious.

[catpartsman]

That’s very interesting of the years you mention. Mine is a 2015 that I purchased new in March of 2015. I wonder if it is a certain factory that has the issues with bracket movement?


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[midwestdenaliguy]

1 hour ago, catpartsman said:

That’s very interesting of the years you mention. Mine is a 2015 that I purchased new in March of 2015. I wonder if it is a certain factory that has the issues with bracket movement?


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That could be it too. They may not have been a problem on all adjustable pedals regardless of year as well.

[Bob985]

Lew just did a tune for me and I have to say im very impressed

[catpartsman]

I really like mine. My brother mentioned how much more get up it’s got than before.


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