77 K10 transfer case noise

[jcondo]

I have a 1977 K10 with a np203, non part time kit.
When I bought the truck the P.O. had taken the speedometer drive gear out of the tail shaft. I reinstalled it and fixed the broken speedometer gear reducer shaft, and reconnected the speedometer gear to the instrument panel.
Now when I put it in gear and hit about 20 mph there is a grinding type of sound. What I wanna know is, what all is inside of the tail shaft when I remove it to inspect the speedometer gear on the shaft?
And if anyone has a parts list with listed parts for the entire np203 that would be great.

[B. W.]

When you remove the tailshaft housing there should be some shims on the shaft (these shims set end play), then the speedo gear. It is a large spiral cut gear on the tailshaft that is plastic. It mates with the long steel gear you have a pic of.

My first guess would be the speedo cable. I've had more than a few go bad, they usually make a rotational noise rather than a continuous noise, sometimes the speedo needle will jump around also. But, if you had to fix the ratio adapter that could be the problem also.

Disconnect the cable but leave the ratio adapter on & see if the noise goes away. If it doesn't, remove the ratio adapter & check again. that will narrow it down.

[jcondo]

Thanks for the reply. I took the ratio adapter off, still the noise. Took the speedo gear shaft out and still had the noise. From what I’m guessing it’s in the transfer case. The only other thing I can think of is it might be because I have it lifted off the ground with the tires in the air.