NP 435 gear noise

[NeverSatisfied]

I know the NP435 has some big gears in it, but I was driving my bronco back from the exhaust shop (been running open headers up to this point) and for the first time I realized my NP makes a lot of gear noise at 3000 RPM+ in 4th gear (running about 65 w/ 4.56 gears). I'm running the 435/203/20 combo and obviously there's a lot of gears spinning inside this group when cruising

I was just wondering if anyone else was experiencing this, or if I have a problem. It's not an excessive noise, but under light load cruising speed it's enough to make someone whos used to the quiet 3 speed/20 combo concerned

 

[Broncobowsher]

That’s a bit strange that you get gear noise in 4th. Considering that 4th gear is a direct shot and doesn’t use any gears. What’s in there is just spinning along for the ride and splashing the gear oil around to keep the bearings wet.

How are the rest of the gears for noise?

You mentioned noisy under light load, are you sure it is the transmission and not axle noise coming up the driveshaft?

With the 435/203/20 combo, are the CV and U-joint angels still good?

 

[NeverSatisfied]

Yeah, I was a little confused by the noise/slight vibration only occuring in 4th. I thought I had everything else pretty well straighted out.

My driveline is only an inch longer that stock, I moved the perches so the pinion is down about 2 Degrees from perfect alignment.

It goes away as soon as I drop below 3000 rpm in 4th or shift to neutral and let the clutch out when running abo\ve 3000

I only used gaskets and seals when I put the 435 back together with the new tailshaft for the conversion. Everything else looked good (for a guy that has never rebuilt a tranny). But one thing that makes me think Im looking at a 435 rebuild is that if I try to grab the 2-3 shift very quickly I get a gear grind (synchros?).

Im thinking my best route is a $165 435 rebuild kit from the graveyard since it needs it anyway. That would at least take one part out of the equation. I hate the thought of pulling that damn 435 again... all that stuff weighs a ton!

 

[68 Broncoholic]

Does it ever pop out of gear?
I bet the rear u-joint is bad too...

 

[NeverSatisfied]

I just might try that U-Joint. If I remember correctly, I think I was missing one needle bearing in one of the caps. The only thing that gets me is it never did it when I had the C4 and no lift in it.

The tranny never pops out of gear. It just does the grind if I go 2->3 very fast and makes a rumble in 4th above 3000. It just really sounds like the noise is emminating from the 435.

 

[45acp]

Its a 435. You're not gonna be able to shift it "very fast". "Kinda quick" is about all itll do. ;D It may need some syncro's, but honestly its just a truck tranny and shifts like one no matter what you do.

 

[Broncobowsher]

The 435 will grind if shifted anything faster then regular. So that is normal.

For grins lets play with some driveline stuff. You say it only happens above 3000 RPM.
Try a lower gear and just hold a high RPM and check that.
Rev it to 3000+ with the transmission in gear, but the clutch pressed in.
Then again with the clutch released and transmission in nuetral.
Then again with the trans in 4th gear and the 203 in nuetral
Then again with the trans in 4th, 203 in gear and 20 in nuetral
Then depending on front driveshaft angle/condition try a drive with the rear shaft removed and driving only on the front axle.

Somewhere in the above you should be able to narrow down where it is coming from.

 

[NeverSatisfied]

thanks for all the input, I'm going to give this a shot tomorrow and I'll report back.

Hopefully I can narrow it down.