My 6-speed manual tranny in my 03 F-350 crew cab 4x4 has developed a worrying noise.
SYMPTOMS: 1) it does not happen until the engine and tranny get warmed up. 2) it only happens in a very limited RPM range, right about at 1500 RPM. 3) It only happens under power, not when I back off and coast. 4) it seems to do it in all gears. 5) it sounds for all the world like some pieces of metal sort of rattling around in the tranny. It is a "light" noise, not like big parts clunking around. 6) I don't believe I can detect any strange vibrations in either the truck or the shift handle. 7) Otherwise it drives fine on local or freeway trips.

One thing that may or may not be important: when we got the truck (used) I drained the tranny and being a dum****, did not read the owner's manual and re-filled with standard gear lube oil. I only realized later that these trannys drink ATF fluid. We changed the lube and it has been in there now for perhaps 6000 miles.

We drove the truck for many many miles with the regular gear lube with no apparent problems.

Anybody out there have a clue? Is the tranny about to self destruct?

Or, alternatively, could it be something else like in the clutch department?

Many Thanks from out here in Washington.

 

Clutch would be my first guess. The ZF sourced trans you have is usually pretty stout. A good though inspection of the driveshaft (u-joints and slip shaft for seizure, looseness) would be a good idea if not done already. I've seen a lot of manuals and t-cases misfilled like you did over the years without witnessing anything blowing up to date. Patience is required for these kinds of noises, tuff to isolate when they only happen under narrow circumstances.

 

Thanks, Chad. Yeh, I figured the standard gear lube did no harm. We have shaken all of the u-jnts etc and stuff still seems tight.

I had heard that the clutch on these is some sort of unusual multi-piece thing. Any chance I'm just hearing slightly rattling clutch parts? Or alternatively maybe the throw-out bearing?

 

The 7.3 clutches were standard single mass flywheels. Not sure ifvthey went back to dual mass for the 6.0. My clutch in my last truck,a 2000 7.3, was rather noisy.