NP435 bearing question

[Lee]

Hi,

Truck is a 1970 F250 Highboy with a 390.... yes a 390 I built from the 360 when I purchased it.

So, about 10yrs ago I rebuilt the NP435 due to popping out of 3rd gear. Purchased an overhaul kit from Novak. Replaced all bearings, seals, and synchro's. Tranny has worked flawlessly for 22,000miles until recently I started to notice a bearing "howl". Makes zero noise in neutral or reverse with the clutch out. Just makes it in forward gears with 4th being the worst. To trouble shoot the issue I have removed the short drive shaft from between the Tranny and the transfer case. No change in noise so it's not a U-joint or the input bearing of the transfer case.

I'm guessing the output bearing on the main shaft. Question of the day is.... why would this bearing prematurely fail? I read somewhere that over torqueing the nut on the rear of the yoke may cause this.

Comments / suggestions are greatly appreciated.
Lee

[Lee]

Update: Pulled the tranny and removed the rear extension housing to access the rear main bearing. First thing I noticed is the extension housing bushing came out with the yoke. It was clearly spinning in it's bore. Supposed to be a press in fit. Pulled the bearing and it feels fine but, since I'm already into it going to replace it. Have ordered seals, gaskets, and the bearing.

[Lee]

UPDATE #2.

Received the replacement parts. Output main shaft bearing, seals, extension housing bushing, and gaskets.

Test fit the new bushing in the extension housing and also on the yoke shaft.

Results: Original bushing is a little bid tighter in the housing, but loser on the yoke. New bushing is loser in the housing but tighter on the yoke.

Going to install new bushing in the extension housing using Loctite 620 Retaining Compound.

[Fraser]

While it's off, I recommend letting a machine shop have a look at the housing, they may be able to knurl it. Or at least measure it and tell you if further action is needed.
They may have other options as well. Re-installing, after the original has been turning could be dicey.

[Lee]

Update: Took the housing to my local Transmission shop. They knurled the bushing and the bore of the housing. Pressed in the bushing with Loctite added. Just have to put it all back together.