Help...New NV4500 mainshaft too small...???

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thrashingcows

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I've been working on getting the NV4500 rebuilt, and converted to 4wd. I just finished assembling the back side of the new fully splined 4wd mainshaft and went to install the rear bearing expecting it to be "tight" and the bearing fell into place!!

I measured my old 2wd mainshaft where the bearing sat and it measure out to 1.877". The new mainshaft bearing surface measures 1.874" and the ID of the new bearing is 1.875".

Any suggestions on what I can do to fix this issue...or should I try and get a replacement mainshaft from the company I bought it from....I bought it months and months ago so I'm sure there will be no warranty, or exchange.

Anyone else run into this issue before?
 
Can you get your hands on another bearing and check I.D. ? Otherwise a good machine shop may have a solution.
 
I tried the new bearing on the old 2wd shaft...would have been a perfect pressed on fit. So I'm pretty sure it's the machining on the new mainshaft.

I would have considered that the bearing was at fault if the measurements of the old and new shafts were the same. But since they are off by .004-ish I have to assume it's bad machining on the new shaft.
 
OK I think things might be usable as they are. I was looking, and thinking about things and noticed that the 5th gear rides against the inner shell of the bearing.

[ame="http://s697.photobucket.com/user/thrashingcows/media/84%20Crewcab/PICT8819_zps6390ad63.jpg.html"]PICT8819_zps6390ad63.jpg Photo by thrashingcows | Photobucket[/ame]

[ame="http://s697.photobucket.com/user/thrashingcows/media/84%20Crewcab/PICT8820_zpsb94cecba.jpg.html"]PICT8820_zpsb94cecba.jpg Photo by thrashingcows | Photobucket[/ame]

Once the nut on the 5th gear is torqued to 250 ft/lbs it should lock that inner shell in place.

Thoughts?
 
I got a response from the company I bought the upgraded mainshaft from...Here's their reply.

HI Brian,

The aftermarket shaft we sell is different in this area. A tight press fit is not required.

When the main shaft 5th gear nut is tightened it draws the bearing cone into the bearing cone so there is not advantage of a tight press for this bearing surface.

We use this same shaft in our own rebuild department and have sold over 3000 shafts with no issues from this bearing journal.

Thank you for your purchase.

Billy
Click to expand...

So I guess it's good to go.
 
Only issue I see with this is that you can't properly set your main shaft end play unless this bearing is torqued down with the 5th gear nut.

Since there is a thrust washer beneath the bearing that needs to be compressed tight, and the other components on the mainshaft that might shift and move once under the load from the 5th gear nut.
 
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