I just bought a 86 dodge NP435 transmission, for 4X4 and decided to overhaul it before trying to put it in service, there are some rust spots on the tops of some gears but nothing major, and have extra gears anyway. My concern is the mainshaft pilot bearing end, there is a swirl pattern on half the bearing surface like I have never seen before, (pics attached). the pattern is clearly visible and with a 10X magnifier it looks like very tiny rust spots, but the roughness is barely detectable with a fingernail, and I tried 320 grit wet or dry paper on it and it didn’t phase the pattern at all still hard as can be, And it micrometers out perfectly round and no taper, the needle bearing rollers all look like brand new and input shaft mating bearing bore is smooth as silk. Should I buy a new mainshaft, or just put it back together with new bearings and seals and run it

 

A picture is tough to tell from. It just looks like discoloration from the picture. Sounds like this tranny has been sitting around for a while. With any tranny cleanliness is next to godliness.

If I understand, we are talking about the end of the main shaft that goes into the end of the input shaft.

The roughness that you can feel with your fingernail. Can you feel it as you drag your nail around the shaft, or along its length, or both? If the input shafts bushing is totally smooth I would not hesitate to reuse the main shaft once the shaft is totally clean. I would not use any parts that the rust cannot be totally removed from. In the case of the gears there should be a wear pattern on them and rust is common outside of these wear patterns on a tranny that has set around for a long time without lubricant being circulated.

 

You know he's talking about a 4 speed manual transmission, right?

 

Yes. Typing is not my strong point. Sorry. LOL

 

No worries, didn't want the OP to be confused

 

Fingernail test defined; I can only detect the slight roughness along it's length, zero on circumferance.

Answer to question; "Can you feel it as you drag your nail around the shaft, or along its length, or both?"

And yes it is the end that goes into the input shaft bearing cavity with the needle bearings.

 

If the roughness is along the length and not around the circumference, the roughness is not rust related as that would be felt in both directions because rust is random roughness. What you describe is wear related. Ultimately you will have to decide how bad this wear is but with this sign of detectable wear I would replace the shaft because I hate to do a job twice. A rough inner bearing race, which is what the end of this shaft is, will eat the new needle bearings over time. JMHO

 

I have now bought two complete 435 trannys, both used but both had rebulders tags on them, and now I cannot build one solid unit. The one in my truck is and has been really growly in 2nd and 3rd so no doubt the mainshaft in it is toast too. Don't know what's up with these bad 435's, maybe bad rebulids? I drove an OEM one (hard) in a 71 3/4 ton PW, shop truck, for over 225K and the only problem I ever had was the two piece snap ring fell out once but nothing else ever went haywire with it. And in the 70's there were millons of them on the highway and normally, damge from undetected fluid loss, or just plain abuse were the only marked failures.

I'm thinkin of going to an automatic, easier to drive, easier to find, less costly for parts, and finally less chance of offspring and grandkids tearing up the rest of the running gears.

 

Have you considered calling the people at monster in a box and see if this is a known problem that they may have an upgrade for?

 

I have always known these transmissions to take ANYTHING you throw at them. It surprises me that you've had this many issues with them.