OK, I've got a real puzzler here. A few months ago this started. During a specific period temperature-wise, I get a loud tapping that's tied to RPM when I put the clutch in.

I had my buddy who has a transmission spot replace the clutch, slave cylinder and throwout bearing...but it persists. Took it to my other friend's shop whose helper has been working on fords forever and he thinks it's the thrust bearings on the crank that are worn, but that sounds a bit deadly to me.

It goes away when the clutch is out at all times. It also goes away when the truck actually gets to highway temp. Stethoscoping you can hear it loudest in the bottom lip of the bell housing and a bit less so in the rear of the oil pan.

I found this thread which seems to discuss in the third response (from IMP), but the OP hasn't been active in years: https://www.f150forum.com/f10/knock-...leased-228978/

Here's a video showing the sound. You can also hear the throwout bearing spinning in the race when the clutch is out, but pay attention to the tapping: https://photos.app.goo.gl/NNWh3z1dqokeSq1S7

Any thoughts? That old thread seemed to suggest input shaft bearing? It's been intermittent for months, and it's driving me crazy. Really hoping it's not a camshaft issue.

 

No one?

 

Did your buddy replace the pilot bearing when he replaced the other parts? In case you don't know what the pilot bearing is, it goes in the back of the crankshaft and the very tip of the front of the transmission input shaft rides in it and the pilot bearing keeps the transmission input shaft centered.

When the clutch pedal is up everything turns together, ie the back of the engine and the transmission input shaft, so the pilot bearing doesn't really come into play. When the clutch pedal is pushed down, the crankshaft keeps turning and the input shaft of the transmission stops turning so the pilot bearing turns and comes into play. If the pilot bearing is rough or maybe not even there or the bearing in it is out it could cause your noise.

The bottom line I suspect the pilot bearing or possibly the guy who has worked on Fords forever is correct.

 

Pilot bearing noise will be present as you engage the clutch.

 

OK, so update is that it's definitely the thrust bearing. After further inspection I've got crankshaft creep. I can move it forward and backward with a prybar.

Now I'm trying to figure out how difficult it would be to replace the bearings with the engine in the truck. I realize that's a bandaid on a gaping wound, but I'm hoping it would get me through this current ****e world sitch where I'm dealing with funding issues that prevent putting in a reman or paying a local machine shop to do a rebuild. Looks like main cap 3 is where the thrust bearing is, but I'll likely just swap em all if I do it since I'll already have the pan off.

I've been searching around on the tubes and found a few vids that show people using little set screws to rotate bearings out while turning the shaft by hand. Anyone have a success or horror story on replacing main bearings while your 302 is in the truck?