Supose you overspeed an actual DAF,MERC,SCANIA,etc engine - like put a wrong gear or during engine brake:
Some say it should be the valves and piston.
Others had broke the clutch,etc.
Seems there is no a pattern.
Any personal experience?
Edzio.
i went from 5th into 1st (ment to go for 3rd) at about 55mph in my rs turbo and bent every single valve in the head, so in my experience the valves go first 
… pistons were alright though, just a bit marked… that was until i turned the boost up and put a hole a in one of them, but that was a different time 
Bearing in mind the reciprocating mass in the bottom end of a large truck engine and depending on how bad the overspeed in question is con rod failure would be a reasonable ( hypothetical ) bet.
Carryfast:
Bearing in mind the reciprocating mass in the bottom end of a large truck engine and depending on how bad the overspeed in question is con rod failure would be a reasonable ( hypothetical ) bet.
Either that or you’ll get a piston up yer backside 
i went out to a broken down scania, the driver was having problems with his gear
when i got there the bell housing had broken and the g/box at a strange angle
got it towed in , to find on the diagnostic computer, said at the time of distruction the eng was reving at 7,000 rpm
it had a sump full of deisel / oil due to an injector leaking
so basically it rev to 7,000 rpm until the rear of the crank,flywheel,clutch snapped off and cut the bell houing off like a circular saw
a new engine fixed it
I’ve often found it pretty impossible to go too far down the box without ramming it in. So unless there are other underlying problems, or you’re a complete plonker, then it shouldn’t happen.
ramhead:
i went out to a broken down scania, the driver was having problems with his gear
when i got there the bell housing had broken and the g/box at a strange angle
got it towed in , to find on the diagnostic computer, said at the time of distruction the eng was reving at 7,000 rpm
it had a sump full of deisel / oil due to an injector leaking
so basically it rev to 7,000 rpm until the rear of the crank,flywheel,clutch snapped off and cut the bell houing off like a circular saw
a new engine fixed it
Do you see some connection between engine overspeed and broken screw from main caps?
Edzio
Cam followers usually fail first on a push rod engine then the clutch drive boss rips out the center of the clutch spinner.Not very often overrevving will destroy a con rod,unless its oil from a failed turbo burning in the cylinders and causing the engine to overspeed.
Edzio:
ramhead:
i went out to a broken down scania, the driver was having problems with his gear
when i got there the bell housing had broken and the g/box at a strange angle
got it towed in , to find on the diagnostic computer, said at the time of distruction the eng was reving at 7,000 rpm
it had a sump full of deisel / oil due to an injector leaking
so basically it rev to 7,000 rpm until the rear of the crank,flywheel,clutch snapped off and cut the bell houing off like a circular saw
a new engine fixed itDo you see some connection between engine overspeed and broken screw from main caps?
Edzio
the only time ive seen maincap bolts is on the 440 scania engine,central maincap between cylinders 3 and 4
edzio…do you have a story to tell .■■ sounds like a true story on your behalf
Drive a auto box and this won’t happen
oneillmartin:
Drive a auto box and this won’t happen
Or a proper manual constant mesh one assuming someone’s really managed to wrong slot a synchro box and put a Scania motor up to 7,000 rpm 
without any con rods letting go but ‘just’ wrecked the crank instead. 
oneillmartin:
Drive a auto box and this won’t happen
If you’re Going down hill not on the power, will an auto shift up at max revs or will it overspeed the engine?
good question i would of said that the pistons & valves would go first but i suppose you would also need to think about wear on other components like has the previous user/ owner of the truck been heavy on the clutch
norb:
edzio…do you have a story to tell .■■ sounds like a true story on your behalf
Yes and no.
Engines like DS11 and TD121 used to bent the push rods as soon you entered the red area.
Modern engines seems more tolerant,not allways a valve will hit the piston - but when they fail
the failure is far more expensive.
Last week I saw a boken crankshaft from a DSC11 (113) where the overspeed was in debate,
just want up to date my knowladge about overspeed.
Everything falls out the bottom of a TS3.
stevieboy308:
oneillmartin:
Drive a auto box and this won’t happenIf you’re Going down hill not on the power, will an auto shift up at max revs or will it overspeed the engine?
On my auto Merc, it starts beeping at you when a downhill takes the revs into or near the red at all.
You have to change up, or more likely brake to bring your speed and revs down.
I haven’t left it to see what happens if you don’t do anything. I figure that, as the driver, doing something is what I’m there for
Bking:
Cam followers usually fail first on a push rod engine then the clutch drive boss rips out the center of the clutch spinner.Not very often overrevving will destroy a con rod,unless its oil from a failed turbo burning in the cylinders and causing the engine to overspeed.
Update had one last night it did not rip out the clutch boss it ripped off the pressure plate tie tags to the main clutch housing so the clutch just kept spinning with no drive to the flywheel.Told by LUK clutches the tie tags are designed to shear under compression to protect the engine.Shot the driver hee hee.
Bking:
Bking:
Cam followers usually fail first on a push rod engine then the clutch drive boss rips out the center of the clutch spinner.Not very often overrevving will destroy a con rod,unless its oil from a failed turbo burning in the cylinders and causing the engine to overspeed.Update had one last night it did not rip out the clutch boss it ripped off the pressure plate tie tags to the main clutch housing so the clutch just kept spinning with no drive to the flywheel.Told by LUK clutches the tie tags are designed to shear under compression to protect the engine.Shot the driver hee hee.
Hi Bking
Thank you for report.
In my experience (I was a fitter in 80’s) with heavy trucks,the first clutch part to go is the linning - burst the linning.
But it may be different for actual systems.
Edzio.
Simon:
stevieboy308:
oneillmartin:
Drive a auto box and this won’t happenIf you’re Going down hill not on the power, will an auto shift up at max revs or will it overspeed the engine?
On my auto Merc, it starts beeping at you when a downhill takes the revs into or near the red at all.
You have to change up, or more likely brake to bring your speed and revs down.
I haven’t left it to see what happens if you don’t do anything. I figure that, as the driver, doing something is what I’m there for
Mine beeps at random times , drops into Neutral at will then beeps but I guess as its done 240000 kms and its a Spatstros its going to seed fast. 