NP203 needle bearings?

[SplitterHD]

Hey everyone,

Apologies if this isn’t the right place for this—I’m new here. I'm currently building a ‘78 K5 Cheyenne and just finished dropping the drivetrain into a freshly painted frame. The setup I’m running is a 5.3 LM7, NV4500, and the original NP203 transfer case.

Since the truck originally had a 350/TH350 combo, I had to swap in a 32-spline input shaft for the NP203 and redrill the case to match the NV4500’s six-bolt round pattern.

Now for my question: How critical is it that every single needle bearing makes it back into the case? The input shaft has around 130 needle bearings, and when assembling it, I was confident I packed each of the three stacks (separated by spacers) as full as possible. However, today I pulled the PTO cover off to reseal it and found one stray needle bearing sitting at the bottom of the case.

Obviously, the correct approach would be to tear the transfer case apart again and track down where I missed it. It was designed to have a specific number of bearings, and clearly, one is not where it’s supposed to be. But the little voice in my head keeps saying, "It’s just one needle bearing… it’ll be fiiiiiine…”

What do you guys think? Is it worth pulling everything apart, or would it likely be okay as is? I do have a 32-spline NP208 as an alternative, but I’ll be adding a turbo soon and figured the cast iron NP203 would be the stronger choice.

Any advice or insight would be much appreciated! Thanks!

 

[76zimmer]

Welcome aboard!
I would consider swapping that 203 out for something better. I’m not sure what, others will chime in, but AFAIC the 203 is only good for the range box on a doubler.

 

[Wes Harden]

Welcome @SplitterHD,

I know the np203 will operate in pretty worn condition, but I haven't been inside one in over 40 years can't answer this. Hopefully some with more recent experience will chime in soon.

 

[tarussell]

Those needle bearings form around that shaft for support of the gear and work as a unit all together - if one roller is missing it will cause the remaining ones to flat-spot instead of continuously rolling around along side its counterparts with minimum friction as it is designed to do.

Each roller works off of its counter part on either side to stay in place creating full support since there is no cage keeping the individual rollers spaced evenly - any gap in the lineup will cause the remaining ones to degrade rapidly thereby polluting the oil and send debris all throughout the case and killing all the other bearings.
And once bearings loose tolerances they can no longer support the shafts/gears as designed and will cause extreme wear/damage to the teeth of each gear - it’s a domino effect that does not end well.

It would be better to have all the bearings worn somewhat equally from extreme high mileage or use than to have just one roller missing. This is not one of those cases where a missing part won’t hurt. Worn parts can still do their job but a missing component will cause damage and failure, especially when it is a bearing!


On a side note: a NV-4500 mated to a NP-203 is a very long setup in a short wheelbase K5 chassis resulting in a very short rear driveshaft - might be something to consider depending on the amount of lift being used.

 

[Chickntrk]

it’ll be fiiiiiine…

Most likely not, the rollers together act as one bearing....I agree with the others though, there are better transfer case options, like any of them. If it were me Id put the 208 in.

 

[SplitterHD]

Thank you all for the suggestions and for sharing your knowledge on this whole thing!

Ive taken your advice and have since removed the NP203 in favor of the NP208 I had kicking around. This actually had the unexpected benefit of allowing me to use some random driveshafts I had laying around from some (unknown) square body. I can’t even remember where they came from but they fit! Might have the get the rear shaft lengthened a bit, won’t know for sure until I actually have a U joint in it.

https://imgur.com/iGWIlwG

NP203

https://imgur.com/VaGEF1B

NP208

 

[Chickntrk]

Love it when a plan comes together

 

[BoondocK5]

When I was building my doubler, I had a few of those needle bearings go missing on both the 203 gearbox and 205.
Rounding them up is a complete shit show as even the places that sell them want to know exactly wear they came from.
I’m just a mechanic that puts stuff back from where it came. With little care of what it’s called and how many are in a replacement bag of them.

What I ended up doing was using my micrometer's and measuring the diameter of what ever needle bearings I needed. Then cutting up a bit of drill rod I had from several harbor freight drill bit sets I had kicking around. I could always get within a few thousandths either side of the correct size. I only needed one or two.
I cut them to length, deburred them, polished them up, and stuck them in there. A bunch of axle grease made assembly a breeze.
Works like a champ.
Some would question this use. But, it’s not a bad choice when you consider that getting the correct ones is next to impossible, and going without them creates a spot for wear.
I’m not concerned about it at all.

 

[SplitterHD]

When I was building my doubler, I had a few of those needle bearings go missing on both the 203 gearbox and 205.
Rounding them up is a complete shit show as even the places that sell them want to know exactly wear they came from.
I’m just a mechanic that puts stuff back from where it came. With little care of what it’s called and how many are in a replacement bag of them.

What I ended up doing was using my micrometer's and measuring the diameter of what ever needle bearings I needed. Then cutting up a bit of drill rod I had from several harbor freight drill bit sets I had kicking around. I could always get within a few thousandths either side of the correct size. I only needed one or two.
I cut them to length, deburred them, polished them up, and stuck them in there. A bunch of axle grease made assembly a breeze.
Works like a champ.
Some would question this use. But, it’s not a bad choice when you consider that getting the correct ones is next to impossible, and going without them creates a spot for wear.
I’m not concerned about it at all.

I mean hey, it’s not stupid if it works right?

 

[SplitterHD]

Love it when a plan comes together

After 6 months of disassembly, planning, and acquiring the pieces, it really does feel good to have the whole thing come together. I’ve been considering creating a build thread but it has yet to be seen if I want to put in the effort lol

 

[76zimmer]

Its worth it to document everything.
I use mine many times to look for what I used for parts or to reference other things of the build! DO IT!