2008 Silverado 2500HD LY6 / 6L90 Transmission Shift Tune

[CNCMachinist]

Very new to HP Tuners. Just got my MPVi3 after going through the last 5 months of hell...

Original trans only had 120K on it (tow vehicle). I had 2-3 and 4-5 RPM flare shifts very early on with this trans. Bought the truck new. Got very bad - to the point where I manually shifted for over a year in order to bring RPM up, then back off on throttle to get it to shift half way decently. About July 2024, it began getting progressively worse. I decided to have the 6L90 replaced before it went completely.

I ended up getting an ETE reman 6L90. Big mistake!! It was installed in September 2024. The reman trans never shifted correctly since installed. Back-and-forth between the trans shop and ETE - never getting anywhere. The "new" trans still has sloppy 2-3 and 4-5 shifts, but not nearly as bad. The new issue is a 1-2 shift that takes over a full second according to my scan tool. All other shifts are between .25 and .4 seconds - depending on throttle position and speed.

I need firmer shifts from this trans. Period. I'd take shift kit style shifts any day over the slow, crappy, clutch-wearing shifts that I'm getting.

Does anyone have a transmission shift tune file for a mildly modified 2008 LY6 6.0L 2500HD used primarily for towing? It would be greatly appreciated!!

Thanks in advance.

[Tech1340]

Post your tune file and I?m sure someone can help you out.

[CNCMachinist]

I've still got to figure out how to do that. It's the most recent GM reflash program for the early 6L90's because I had to pay $250 to get the TCM reflashed after the reman trans installation.

[Alvin]

You shouldn't have to tune for a reman transmission assuming it was flashed for your vehicle in the first place.

[RDF1]

This is like putting a bandaid on a femoral artery bleed. There is a reason the transmission is acting the way it does.
A factory tune should operate the transmission just fine. You either have a valve body issue or a internal issue that needs to be addressed before trying to put the bandaid on which wont last long.

[CNCMachinist]

Not really. The first gen 6L90's have these same issues - Inherently and very often. It's not a coincidence that the orig trans AND reman trans have the same issues. I have heard others say the same thing. The factory programs for these early 6L90's do not address the inherent issues...

[Tech1340]

A friend of mine has the same truck. His had similar issues and I’ve been able to make it a lot better by adjusting shift time and shift scheduling. Also, Have you tried to reset the adapts through the scanner?

[DodgeBoy_8HP]

Very new to HP Tuners. Just got my MPVi3 after going through the last 5 months of hell...

Original trans only had 120K on it (tow vehicle). I had 2-3 and 4-5 RPM flare shifts very early on with this trans. Bought the truck new. Got very bad - to the point where I manually shifted for over a year in order to bring RPM up, then back off on throttle to get it to shift half way decently. About July 2024, it began getting progressively worse. I decided to have the 6L90 replaced before it went completely.

I ended up getting an ETE reman 6L90. Big mistake!! It was installed in September 2024. The reman trans never shifted correctly since installed. Back-and-forth between the trans shop and ETE - never getting anywhere. The "new" trans still has sloppy 2-3 and 4-5 shifts, but not nearly as bad. The new issue is a 1-2 shift that takes over a full second according to my scan tool. All other shifts are between .25 and .4 seconds - depending on throttle position and speed.

I need firmer shifts from this trans. Period. I'd take shift kit style shifts any day over the slow, crappy, clutch-wearing shifts that I'm getting.

Does anyone have a transmission shift tune file for a mildly modified 2008 LY6 6.0L 2500HD used primarily for towing? It would be greatly appreciated!!

Thanks in advance.

Can you share the tune and a log?

I can remote support you

[CNCMachinist]

I spent the better part of last weekend reading everything that I could about tuning for my application. A YouTuber (who shall remain nameless) absolutely pointed me in the wrong direction and my initial trans tune was terrible. Worse than it already was. So, I grabbed a cup of coffee and went to work writing my own trans tune for my 6L90 ? step by step. Not bragging, but my finalized trans tune is just about perfect. Everything comes on right where I want it, and feels like I want it to.

So then I decided to tweak the engine a little. My truck is basically stock except for K&N Cold Air Intake and DynoMax exhaust. I opened up PE and got that dialed-in first. Then, I added a little timing ? but nothing crazy as I run 87 octane. Again, what a difference!! Especially at WOT. I am so happy with my HPT purchase and the results of some research and work. Many of you helped TREMENDOUSLY with some of your past posts and/or replies.

Please feel free to critique my tunes and advise if there is anything that I have overlooked, or if something does not look right. I very much appreciate it!!

[bmpcamry09]

Engine side could use a lot more. All you really did was enable PE. Also, you added timing to the low octane which doesn't do much for you because it reads off the high octane until knock is detected. Start with the high octane table and datalog before touching low octane. A ton of stuff in torque management that can be done too.

I can get you a starter tune to point you in the right direction. $100. PM me if interested. Just finished a 2011 and 2008 truck in person locally and have a good starter file for trucks just like yours