Good afternoon All! My name is Frank and I am the owner of a 2024 3500 Denali Ultimate with the 6.6 DuraMax.

I'm going to be towing an RV and would like to monitor what gear the truck is actually in. I have several apps on an iPad and NONE of them can read the TCU to tell me the actual gear (actually, none of them have any of the 2024 specs in them). Can anyone tell me what I can do to read the actual gear of the truck (putting the transmission selector in "L" shows the gear but you must shift manually and I really don't want to shift into "L" at 65 mph). I have gone to the OBD-II sections of the forum and have not been able to find anything regarding the 2024 species. the DuraMax also has a new variable two vane turbo that would be nice to monitor also. Can anyone help me out?

GMC Denali Ultimate
6.6 DuraMax
Allison 10 speed
4 Wheel Drive
Short Bed
Crew Cab

Thanks in advance,

Frank

PS: the service manager at the dealership told me that PID'* were only for Fords ???

Congratulations!

I don't know of a way to do this. I've seen it in F-150s for years, and a couple of Suburbans I rented years ago also did this and showed V-8 and V-4 operation. I can't find a way that your vehicle would do this, nor a way to get this though OBD2 except perhaps with a $5k Snap-On diagnostic tool.

From page 85 your Sierra/Sierra Denali 2500 HD/3500 HD Essential Operating and Safety Information manual:



Like a boost gauge? . . . or a tachometer for your turbocharger?

I'm a little leary of putting the transmission into manual mode (shifting to L) for a couple of reasons. 1. what if it actually downshifts to L when i'm doing 70 with 15000 pounds of RV behind me. 2. putting the transmission into manual mode means I need to shift by using the buttons on the selector. What I would like to know is when i'm driving down the road (either normally or with RV) what gear the truck is actually in.

I suppose that if I place it in manual mode, select 10, then it MAY tell me what gear it is actually in. I have placed it in manual mode a couple of times and the truck actually starts out in third or second gear. meaning it can pick any gear from that number down. Since it shows on the console, there MUST be a PID that tells what gear the truck is in while in Drive.

I have yet to attempt the manual PID that was suggested earlier, possibly tomorrow.

THanks,

Frank

You can select any gear but the computer will not engage until specific parameters are met. When things like vehicle speed are over the set parameter for that gear range it will not engage that gear until that parameter falls within the program limits.

Understandable, but keep in mind that these are not the hydraulic/vacuum-controlled units of yesteryear. If shifting to L caused it to shift to a ridiculously-low ratio, you'd hear of blown engines, transmissions, car wrecks, etc. all the time with these. Thanks to the computers they put on board, the engineers can keep things like this from happening.

Referring to "L" like this implies that the "L" range selection of the lever puts the transmission in the lowest possible ratio. It doesn't. It refers to Lower ranges. This is one of the indirect results of prindles getting too big. Remember when it was P-R-N-D-L2-L1? Click click click you're in Drive. Want manual 1st for whatever reason? Another click click and you're there. Then overdrive came along. GM added a click. Other manufcturers did various things including a separate overdrive button. Regardless, Click click click you're in Drive. Another click click click and you're in manual 1st.

Then . . . the 6-speeds showed up. Nobody wants Click click click click click click click click to get to manual 1st, let alone the swing of the lever probably pointing at the transmission hump. Let alone doing this while driving. They had to be practical and fins another control to select range.

Now . . . the 10-speeds are here. Nobody wants Click click click click click click click click click click click click to get to manual 1st, let alone the swing of the lever probably pointing at the brake pedal. Let alone doing this while driving. They had to be practical and fins another control to select range.

Actually no. It means you can select the highest gear that the transmission will allow while operating in L (Manual Mode). All gears below that number are available. As driving conditions change, the transmission can automatically shift to lower gears. For example, when L5 is selected, 1 (First) through 5 (Fifth) gears are automatically shifted by the transmission, but 6 (Sixth) cannot be used until the plus/minus button on the shift lever is used to change the range.

This is the same behavior as the Turbo 400s, Turbo 350s, and 4T6x transmissions. This is also the same as the 4L6xs, except the 4L6x could do second-gear start when 2 was selected and would stay in 2nd unless the driver put their foot down far enough at too low of a speed, then it would declare how stupid the driver is and downshift to 1st.

I believe this is not available without a $5,000.00 diagnostic tool of some sort.

Not on the display. You will only know by counting shifts.

Just like described above, but let'* get the wording right or we might end up on a tangent. When you place it in manual mode while stopped, it starts out displaying the highest gear that the transmission will allow, but is actually engaged in the lowest gear ratio. If you release the brake and accellerate, it will shift 1-2 then 2-3 then not shift any higher.

I, like you, had a hard time "losing" the ability to know what gear my transmission was in with the electronic selection. Then, I realized that I have the same as before, just with up and down arrows or +/- buttons. My 1985 C30 never indicated what gear it actually had engaged. My Yukon never did either. I just told it the highest gear it could use with the lever. Now it is buttons.

I will say, yes blasphemy here, that Ford offers an [actual gear engaged] display on some or maybe all of their pickups. Well, except the Lightning of course.

I suggest your best bet is to find a quiet road somewhere, and try this out at progressively faster speeds until you have a feel for it, then let the automatic transmission be automatic with your top-ratio-available guidance.

Banks Super Guage setup will allow you to monitor a gazillion parameters. You can setup 7 screens in each Guage. I have two. One always reflects RPM, trans gear, torque converter status i.e. Locked or unlocked, and boost pressure.

The other Guage I have a pages setup for:

Temps: EGT1, EGT 5, trans, oil, coolant, fuel rail, and intake air.

Pressure: i.e. Oil, fuel rail, boost, DPF, ect.

Emissions: DPF percent, DPF regen status, avg regen mileage, avg DPF Time, etc.

Anyway it'* a sweet setup. They have a Guage cluster that mounts through the existing fastener for the grab handle. I can send you some pics and whatnot if you are interested.

I've also put all the other Banks parts of my truck except the new air horn i.e. CAI, boost tubes, exhaust, derringer, and pedal monster. I generally run the pedal monster off for commuting and the derringer on lvl 2. It'* a sweet setup. Seen an increase in mileage, 2-3. Put the derringer in lvl 3 or higher and the pedal monster in street mode and it'* wild. Banks has their stuff together.