Hey guys! A new truck with new symptoms has once again brought me out of hiding. I saw a truck today, and bought it. It seemed like a dandy, but on the way home developed a problem.

Truck:1995 Powerstroke F-Superduty. 5 speed, granny gears (Max of about 70 mph) Has a 12' electric over hydraulic dump. 236xxx miles. Very slick old truck.

I bought the truck knowing it has a draggy starter. No biggie. It was running like a scalded dog, but coming up a hill a little over half way home, it developed a vibration. I thought sure it was a u-joint, just because I'm a veteran with those. It got worse, and I didn't think I would make it home. I have narrowed this down to Pre-clutch. I was pushing in the clutch coming home and coasting down the hills at idle, because it made the vibes go away.

But, even with the clutch in it will shake the whole truck when you rev it up. It is smooth as a kitten at idle, then terrible until about a grand, not as bad till 1500, then the higher you go the worse it gets. However, it still runs smooth the whole time. This does not seem to be related to any kind of miss, ect.

Is it possible this in in the flywheel? Harmonic Balancer? Or am I way off base?

Please help.

 

 

Does it still have the dual mass flywheel?

 

I honestly have no clue. Is there any way to tell?

 

Remove the inspection plate and try to rotate the flywheel. If it moves, that's the two masses moving relative to each other ==> ready to let go.

 

When you shut it off do you any clanking coming from the clutch area?

 

Sounds like DMF to me.

You can feel it in the clutch pedal if you put a little pressure on it.

 

By it not doing it while its cold, could that suggest harmonic balancer? I can't really feel it in the clutch. It didn't show any sign if trouble until about 25 miles down the road.

 

typical dual mass flywheel.
when cold they work properly. once hot they start to do all kinds of weird things.

i had one that would smoke the tires if you did a third gear clutch dump cold.
once hot you could let the clutch out in fifth gear at a stand still with no throttle and the engine would not even loose any rpms.

 

My DMF vibrated the whole truck too, exact same symptoms as the OP described. That's where I'd put my money...

 

There are clutches in the actual DMF itself, if they heat up they break loose.

 

So how do I know for sure? And will I need to replace the clutch while i'm at it?

 

I've had a few 6 speed 99.5 trucks, but this is my first obs manual 7.3.

 

Yes, you'll need a new clutch, pp and flywheel if thats the case.


I got a side DMF picture around here someplace.

It's pretty obvious when you have one.

 

See "inspection plate" reference above ^^^^^. If the truck's on it original clutch at 236,000, that's about as long as two clutches usu. last. And more generally, unless you know it's VERY new, it's just smart to do it while you've got the tranny out.