My F350 Powerstroke Diesel 5-speed manual has developed a perplexing problem that is getting worse. If I put the truck in Neutral, and take my foot off the clutch, the engine starts to make a horrible rattle, which shakes the entire truck. If I put my foot on the clutch, the rattle goes away. This only happens in Neutral. When I’m driving, there is no particularly noticeable rattle, and the truck seems fine. The only thing I can think of is a worn pilot bearing, but one would think that would affect in-gear operation also. Any ideas?
Not a pilot bearing. That can’t make noise with the clutch engaged (foot up), as then the crankshaft, clutch disc, and tranny input shaft are all clamped together.
If it’s truly an engine noise, I’d say it would have to be a crankshaft thrust bearing problem. This is pretty rare.
More likely it’s a transmission noise. The tranny input shaft bearing is the prime suspect. With the clutch disengaged (pedal down), the shaft can sit still in its bearing while the crank and pilot bearing spin around its forward tip. Pedal up, that shaft has to turn in its bearing. Typically the noise would totally disappear in direct drive (usually 4th gear) when the input shaft is directly coupled to the output shaft, which then supports the input shaft near its bearing. It would still be present in other gears, but to a lesser extent than in neutral.
Well, by putting your foot down on the clutch pedal what’s happening is the disengagement of the clutch assembly from the flywheel. However, if the noise isn’t present while driving, that would seem to rule out a bad clutch/pressure plate. There isn’t much else left in that area except for the bearing. Obviously, I’m no help other than rendering an opinion similar to yours.
You didn’t mention the model year. There are at least three generations of powerstrokes. I’m very well versed in 1st gen. These have a dual mass flywheel, not sure about the later ones, but guessing all the V-8s do, maybe not the V-6s. Sounds like yours may be going south.
Luk sells a simplified replacement if the OEM replacement is too rich for your blood.
It’s a 1995.
In retrospect, I should have known it was first gen. as the later ones got 6 speed gearboxes. A '95 is almost a slam dunk that the dual mass flywheel is shot.
Essentially this two flywheels coupled by springs. Meant to dampen torque fluctuations, and make life a bit easier for the transmission. There is a plate on the bottom of the bell housing that makes inspection easy. Don’t have the specs handy, but there should be little radial slop between the two, and no play in the bearings that support the rear mass.
The 8 cyl powerstrokes obviously have 8 cylinders, but also rev pretty high for a diesel of such displacement, so the torque spikes are not near as bad as many other diesels…I’m looking at you Cummins! By all accounts the ZF-5 survives OK with the plain Luk flywheel.
Two tips: If you have a dealer do the work, be very insisting that they NOT re-flash the ECU. Yours has probably been done already, but 95-96 owners who got the “upgrade” are universally disappointed…less power, lower fuel milage. Apparently there is no going back either.
Second, If you do the work yourself, rent a stout transmission jack…makes it almost easy.
Plenty of experts here:
http://www.thedieselstop.com (I might know member #17)
Thanks for the tips. I’ll take a look at it, and if it’s the flywheel, I’ll do it myself when I get another vehicle up and running (always something, isn’t it?).
You should crawl under there, pull the inspection plate, and have a look/feel at how bad it is. Get an idea of how long you can put off the repair. If pieces of broken springs fall out when you take the plate off, you maybe aughta take care of it sooner than you were thinking.