Fuel Cutoff / 5th gear lockout question (6spd ally with lbz)

[madden]

Here's what I want to do: I'd like to run through the traps in 4th gear at around 3900 rpms on the drag strip. My theory is that this will reduce damage to the C3 clutches by keeping it out of 5th gear. I know that the best power is to be had at around 3200 -3400 rpms but this theory is centered around having fun at the drag strip without limping.

On my LB7 there is a tab under engine>fuel control>fuel shutoff> RPM Limits. This tab does not appear on the LBZ. One thought that I have was to tune the tranny to shift at the desired rpm at the 4>5 WOT upshift. I guess I could do that in the tow/haul mode only and then you could use the tow/haul button when you want to quarter mile race. Is this how I should tune the LBZ to run up to 4100ish rpms in 4th gear or am I looking in the wrong direction?

[trentnell]

Here's what I want to do: I'd like to run through the traps in 4th gear at around 3900 rpms on the drag strip. My theory is that this will reduce damage to the C3 clutches by keeping it out of 5th gear. I know that the best power is to be had at around 3200 -3400 rpms but this theory is centered around having fun at the drag strip without limping.

On my LB7 there is a tab under engine>fuel control>fuel shutoff> RPM Limits. This tab does not appear on the LBZ. One thought that I have was to tune the tranny to shift at the desired rpm at the 4>5 WOT upshift. I guess I could do that in the tow/haul mode only and then you could use the tow/haul button when you want to quarter mile race. Is this how I should tune the LBZ to run up to 4100ish rpms in 4th gear or am I looking in the wrong direction?

just raise the 4-5 shift to 110 mph and rpm to 3900 rpm in t/h table but rev this high at your own risk i have done it but you can have valve train failures.

[madden]

just raise the 4-5 shift to 110 mph and rpm to 3900 rpm in t/h table but rev this high at your own risk i have done it but you can have valve train failures.

Thanks man,

I've been researching the safe rpm limits of the stock duramax block and have found that this should be pretty safe.... most folks just don't care to spin the motor above 3500 because it does not make the best power beyond that. I've even found that the engine braking feature will "push" the rpms to beyond 4500 on a steep downgrade. (It's only freewheeling the engine in this situation (no fueling) but the internal parts are still turning that fast.

[madden]

By the way trent, are you shifting at around 3500 rpms on your 12 second passes?

[madden]

just raise the 4-5 shift to 110 mph and rpm to 3900 rpm in t/h table but rev this high at your own risk i have done it but you can have valve train failures.

I tried this and the truck will not fuel beyond the stock shift point. Being that the fuel tab is blank on the LBZ (as opposed to the LB7) I'm not sure what needs to be done. Can anyone help?

[madden]

Being that no one from HP Tuners is chiming in on this thread can I assume that the software will not allow me to do this on an LBZ? I wish someone from "@HPTuners" would at least respond to this thread.

[Programmer]

Post your file so someone can look at it.

[madden]

This is the last file I tried. It will remain in 4th gear @ wot (in t/h mode) but will not fuel past the stock shift point.

[madden]

I tried the changes and the truck still will not fuel beyond the stock rpm limit. It runs about 88 mph in 4th gear with 265/75/16 tires and then shuts down. The file is attached.

[Programmer]

I'll try get this fixed up for you tomorrow...

[madden]

I'll try get this fixed up for you tomorrow...

[Programmer]

No guarantees...I need you to test it. Pull your TCM fuse prior to the reflash.
If you get an error message "Index out of ..." you need to update your HPT to the newest beta by contacting support at hptuners.com.