NP-435 Grinding in first. - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 01-11-2009, 07:16 PM   #1 (permalink)
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NP-435 Grinding in first.

My early Bronco has a NP-435 that was running fine until I pulled it out to fix a leak. Like a dumbass I grabbed the output shaft and pulled it to get the trans out. The shaft and the bearing both slipped out about 1-2 inches and then slipped right back in. Now I've got everything back together and it all works fine but has a grinding noise when I use first gear.

So what did I fuck up? And how do I fix it?
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Old 01-11-2009, 08:09 PM   #2 (permalink)
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First is a straight cut gear. It may make a whining noise, same with reverse. Now if it's actually GRINDING????
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Old 01-11-2009, 08:27 PM   #3 (permalink)
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It never made this noise before I slipped the output shift out.

While I had it out it fell off the floor jack and landed on it's side as well.

It definately sounds like two gears are hitting each other. It only makes the noise when it is in first gear and the Bronco is moving. All other gears are fine and don't make any noise.

Could the shift forks/gears have become mis-alighned or something?
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Old 01-11-2009, 08:42 PM   #4 (permalink)
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output shaft is also the main shaft. I am guessing when you pulled on it, you dropped the pocket bearings that go in back of the input shaft that the mian shaft rides on.

http://www.drivetrain.com/np435_p1.jpg
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Old 01-11-2009, 08:42 PM   #5 (permalink)
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This diagram shows a "first-speed gear stop" on the mainshaft. Maybe that thing moved.

http://www.motorsport.wlrgroupco.com/np435fsmdiag.JPG
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Old 01-11-2009, 08:45 PM   #6 (permalink)
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output shaft is also the main shaft. I am guessing when you pulled on it, you dropped the pocket bearings that go in back of the input shaft that the mian shaft rides on.

http://www.drivetrain.com/np435_p1.jpg

Sounds like the damn thing will have to go to a rebuild shop. I aint got the coin for that right now.
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Old 01-12-2009, 08:18 AM   #7 (permalink)
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You can always try rebuilding it yourself. A friend of mine rebuilt his for around $165 in parts. He isnt that mechanically inclined either and his holds up to his built 460 and heavy right foot.
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Old 01-12-2009, 11:34 AM   #8 (permalink)
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Sounds like the damn thing will have to go to a rebuild shop. I aint got the coin for that right now.
this is very easy to check out. drain the fluid and see if there is any roller bearings laying in the bottom from the pto cover. If there is, put them back in the input shaft. it is easy.


you might be able to lift the main shaft from the pto cover or you might have to take off the shift cover to lift it. Remove the input shaft put all the bearings back in the pocket, use grease to hold them in. reinstall input shaft using the same shims that were behind the retainer.
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Old 01-12-2009, 01:43 PM   #9 (permalink)
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The bolts that hold the tailhousing on are different lengths. If you put a long one in the wrong hole it will hit the gear in first.
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Old 01-12-2009, 04:14 PM   #10 (permalink)
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The bolts that hold the tailhousing on are different lengths. If you put a long one in the wrong hole it will hit the gear in first.
Wow, I hope thats it. Where do the short bolts and long bolts go?
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Old 01-12-2009, 04:48 PM   #11 (permalink)
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Wow, I hope thats it. Where do the short bolts and long bolts go?
That would be my guess too. It's the lower left it looking at it from the rear if I'm remembering correctly. It's been a few years since I did the EXACT same thing.
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Old 01-14-2009, 05:43 AM   #12 (permalink)
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The bolts that hold the tailhousing on are different lengths. If you put a long one in the wrong hole it will hit the gear in first.
It worked! I backed out the lower left bolt and drove it, no grinding!! I'm very stoked! I was ready to take it out and have it rebuilt. Thanks Q & D I owe you a few cold ones, just let me know what flavor and where to send em!

And thanks to Rockit for telling me which bolt to shorten, that saved me some time too.

Now if I can just figure out my brake problem I can go wheelin!
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