I rebuilt my engine from a 351M to a 400 in 2018. While out, I upgraded to the larger clutch/flywheel, replaced the pilot and throw out bearings, and things went back together just fine. I cannot recall exactly when the noise started but I would hear a loud rattling between 3rd and 4th gear and every now and then, there'd be a loud bang, almost like a gunshot underneath. No issues other than the noises were observed.

I was pulling trees this past spring and rode the clutch a little hard and could smell it burning so I decided it was time to take things apart. I went the route of taking the t-case and trans out from below (I'm fixing some rust and repainting the bed as well so the bed is currently off.). Given the NP435 is 40+ years old, I sent it off to the local tranny guy for a once over for cheap insurance while things are apart. Upon pulling the bell housing, the throw out bearing was laying in the bottom. I can't figure out how this happened. The crazy thing is that I could shift just fine. The fork has some light wear but nothing significant. It's attached and seems to be functioning fine.

I'm going with the Centerforce dual friction setup this time. I have enough engine mods that I need a little more oomph and I have no plans of taking this apart again any time soon. I will replace the fork but this is one of my questions. I see two listed for my truck: before/after DG0,001. Given that my truck is a hodgepodge of all different years, I have no idea what it actually is. My existing fork matches the "before" style but maybe that's not the best fit? Engine size seems to have no impact on which is used. The only difference I can tell is that the "after" has a tang that appears to stick out farther for the spring. I'm wondering if it is also longer and I need the length? What else could cause the throw out bearing to come off? My adjusting rod was replaced in 2018 as well. It was slightly bent.

While browsing threads, I see where people have had their fork pivot come off the bell housing. Mine seems fine but would it be good insurance to pop the rivets out and replace with screws now while I can?

 

These clutches can take a lot of abuse and still run. My TO bearing also hanging loose and the fork retainer spring was broken off.

Since the fulcrum/pivot was very wobbly, I tapped the bell and pivot for 3/8-24 fine thread and used counter-sunk screws, with red loctite, washers and nuts.





Not going anywhere!

 

Seems like re-securing the pivot mount is a no-brainer. I'm so glad I looked here before reassembling. Thanks!