Anyone know what the redline is? my tach says 5k, but when i get on it the most i have seen was just under 4k. What is the highest safe RPM to spin the dmax at?

I think 3,250 is about max, 5,000 is max when down shifting to slow a load on a hill.

EFI will allow you to rev out alot more.....and put a smile on your face!!!!

3,450 RPM is all it will fuel to. 3,250 is the max it will upshift at under power.
Test it for yourself- P or N and wood the throttle. No, it won't hurt anything either.

max grade braking is 4650

max grade braking is 4650

I thought it was 4800 on the LBZ's for grade breaking, I could very easily be mistaken though. I haven't ever had mine down shift nearly that high while loaded.

yeah iv seen max like 3850 with my edge on 5

The safe RPM for the rotating assemblly when NOT under power load (on the fuel) is just under 5000 rpm. This is based upon the physical properties and characteristics of the crank, rods, bearings, etc.

The stresses induced while under power (using the throttle) are much different than those of free-rotational energy. The factory tune from GM would never create enough stress to ever hurt the Dmax bottom end; it's quite well engineered when used in stock form.

That is why there is a difference of rpm for what you'll see on a downshift versus an upshift.

What you do to your engine under power load and a tuner is up to you. I cannot comment on where the safe limit is for a modified Dmax when fuel above factory tune.

I thought it was 4800 on the LBZ's for grade breaking, I could very easily be mistaken though. I haven't ever had mine down shift nearly that high while loaded.
Opps, your right chris, I had a thought that it was wrong, but posted anyway :D
Boy to the EGT's drop when your at 5k :lol:

I thought it was 4800 on the LBZ's for grade breaking, I could very easily be mistaken though. I haven't ever had mine down shift nearly that high while loaded.


So it's ok for the motor to rev up to 4800 rpm while using the grade braking feature? I always freak out when it stats downshifting too much and reving up the motor. I then turn off tow/haul mode and switch over to manual to keep the revs down. I figured since these are diesels we shouldn't over rev past 3k for extended times down long grades.

All is well, leave it in tow/haul and let it rev. We have been over this on here before,too. The truck, if stock, is way smarter then we are. It will not allow itself to inflict any pain. It will up shift or whatever it needs to do, to stay in a "safe" zone for itself. You can even be going 90mph and manually drop the trans down to first gear, and the tranny will only drop down as far as is safe for the engine. They are friends and chat with each other about what you think you want to do. Then they let you know what they will do.

Thats good to know, on the weekend I was towing in tow/haul mode and it down shifted and went up to 4500 rpm. I quickly took it off tow/haul and hit the brakes,changed my shorts.lol