O.T. Calling Ford ZF 6-speed experts

I just replaced the clutch, flywheel, pressure plate, T/O bearing, pilot bearing, clutch fork & pivot on our 2001 F350 diesel truck (SRW, 4x4). All parts came from South Bend. Transmission now shifts perfectly, but at idle, in neutral and with clutch engaged, I hear what I first thought was T/O bearing noise, but when I disengage the clutch (apply the clutch pedal), the noise disappears. Before I did the clutch job, this noise was also present but at a much lower volume.

Now, I'm wondering what the likely source of this noise is. It sounds like a bearing rattle or light growl (or gear chatter) and if I throttle up a little (1250-1500 RPM), it goes away--it seems to only happen at idle. When I removed the OEM flywheel, the pilot bearing was missing some needles and the input shaft did have a little wear but it still had a good fit with the new pilot bearing that came with the new flywheel. I polished the input shaft and also used lube for the install.

If anyone could offer any information or advice, I would be grateful. My son & I did the job and those that have done the same job before us know its a fairly big one to drop the ZF transmission w/transfer case, so I don't really want to do it again unless its necessary. At the same time, I don't want to damage the transmission with continued use, if one of the internal bearings is bad.

The noise will be the input shaft bearing and/or the first gear inside the transmission case,,probably a bit of both.

There is a kevlar pilot bearing available for these and it will outlast several needle bearings. An added plus for the kevlar is, it will tolerate some damage to the trans shaft.

LUK or Southbend should have them.

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/zfs640_inputshaft.jpg">

My vote is for the input shaft bearing or the mainshaft pilot bearing.

Of course, the countershaft bearing are a possibility, as well.

If its the sound I think youre describing, my 01 made the same noise. Does it sound kinda like a power steering pump that low on fluid, but not as loud?

Bob,

When we had the transmission down, I checked side movement of the input shaft and there was none. I was thinking about maybe the mainshaft pilot bearing was more likely. Also rotated the input shaft by hand and it spun freely and with no noise...What confuses me is the way the noise goes away when I throttle up the engine...

I suspect that with the new clutch disc the new circumferential spring dampers in the disc are allowing higher amplitude engine firing torsionals are getting through to the transmission. These torsionals are causing all the loose parts to rattle inside the transmission. Loose parts being free play between the gears and also axial or end play on all shafted gear sets.
Gear rattle

I think Vern is right on the money...........My friend replaced the clutch in his "ZF" equipped service truck a few years ago and ended up with the same results as you, more noise from the trans. than when he started..........

If it's any consolation he drove it for several years before he sold it recently........to my knowledge it's still running...........

I believe ATF is the recommended lube for those transmissions but I think I've heard of people mixing 50% ATF with 50W manual transmission oil to help reduce noise??