Highest RPMs should go?

Finally a good answer.

I spoke with a Detroit engineer about the DD15/DT12 combo and the high engine speeds while on the engine brake going down hill.
2200 is what they are rated (and designed) for. Over that can damage the engine.
And don't try to get more than 1700 while accelerating unless you want to blow something up.

Letting it get to 2700 is just careless and sloppy.
And the OP would NEVER have let it happen if it was his own truck.

 

Ok, so the real question..
How fast were you going at 2700rpm.?
Let's say you was in the big hole. Seems lots of the new rigs are geared to run about 65mph @1200rpm or so. If that's the case, at 2700rpm, my math says 146.25mph.. How bout it..

 

Lmao . Man that would be fun

 

What would you consider a huge mountain?

 

1800-2200 is normal on the DD15 and DT 12 transmission. You don't want to go over 2400 you should get dash warning at 2400 about. I would guess at 2700 or 2800 engine might start coming apart. They never say what Maxx is it can handle.

 

Some of ya'll act like hitting 2,700 is an instant death sentence for an engine. Probably didn't even phase it for the couple seconds it happened.

 

TBF, I don't even think the tach in the last truck I drove went that high... if memory serves, it topped out at 2500

 

If the engine is running normally if it is still pulling all should be well. You might have taken some of the miles off the engine's life. I also agree about the electronics that will tattle on you. I used to tell green drivers all the time. Learn what your engine's operating RPM range is. Take a marker and mark right on the glass of the tach. REMEMBER! This is of critical importance! Operating an engine UNDER the recommended RPMs "lugging" is just as bad as going over. In fact, I have spoken to some diesel mechanics that swear they see more damage from "lugging" than most anything else.

 

Been preaching this the last 25 years with the new lightweight diesels everyone installs in boats .

I actually killed a year old 30 thousand dollar motor from it being lugged.

Marine specs called for max rpm 36-3800 rpm. This is a 4 liter 6 cylinder diesel marinized by yanmar , Toyota excavator motor that is no longer in production .

I had it propped for 3700.

Exact motor I bought to replace it a year later specified max rpm 4-4200


Many people buy the new boats with the lightweight high rpm diesels and think they have a Real Engine. .

Than the Misses loads up 2000 pounds of clothing and cookware into the thing along with the 40 cases of beer the Captain keeps at hand at all times along with the friends and kids invited and now the boat is 25% overweight.

Out they go every weekend cruising at 85% rpm just like the dealer told them to do.

Except the throttles are Mashed to the wood to maintain the Safe rpm. .

Heck I've seen small sailboat motors Roached from over propping and lugging .

 

It's not just Marine applications either. Most larger prop aircraft have what is called a constant speed prop. While flying you have to "set" the prop to match the engine manifold pressure. If a pilot makes a mistake and does not set that prop back upon landing, it is possible to destroy one of the engine "jugs" because of the backpressure if by chance the pilot has to apply full power after a landing abort. I have seen a pilot destroy an engine in a Cessna 182 at the Peachtree Airport near Atlanta because they did this. I still remember that pilot screaming mayday mayday to the tower. That guy almost busted his butt that day. So yes, careful and easy does it when it comes to operating these engines!