I've been thru the whole speedometer cable, had it out checked and lubed, if I pull it out of the transmission I can spin it freely and it moves the speedometer just fine if I spin it fast.
The little plastic gear at the end of the speedometer looks just fine, and I can feel teeth inside the transmission - the only thing I can think of is that the gear on the inside of the transmission stripped out.
Anybody know how to get that gear out, or know how to figure out if its stripped?
I had one apart on an NP435 transmission a few months ago, but the trans wasn't in a truck at the time.
If you can shine a light in the drive hole, you will probably be able to see if it's damaged.
To replace the NP435 speedo gear, I removed the yoke from the tailshaft, unbolted & removed the tailshaft housing, removed a circlip from the tailshaft & slid the drive gear off. It engaged on a small pin to drive.
You would need to support the transmission & unbolt the rear mount from the crossmember to do this, if still in the vehicle. I didn't have to bother about that, or even drain the oil, the trans was just sitting on the shed floor.
The tail housing is held on by 4 bolts. the speedometer gear is nylon and is colored to match the transmission. the nylon gear is on the output shaft and held on by two c-clamps, one in front and one in back. You will need a special pair of plyers to remove the c-clamp. The gear will slide off. WARNING. Do not pull on the shaft without the tail housing in place or it will separate from the transmission and the inter roller bearing, that you can't see, will spill into the transmission causing more problems. The tail houseing holds the output shaft in place and the shaft must not be allowed to shift backwards!! When you take the tail housing off there is nothing holding the output shaft from coming out the back.
All the four speeds are relatively the same to get at the speedo drive gear in the transmission, T-18, T-19, and NP-435.
It's color coded depending on how any teeth the gear has. Either 6, 7, 8, or 9 depending on the rear end ratio, and the cut to the teeth, either left or right handed. This is different to the speedo cable gear on the end of the cable that is also color coded with teeth rangeing from 16 to 21 teeth and is to be matched with tire size.
You need to know the current rear end ratio of the truck, and/or the color of the gear inside the transmission to get the right one, or to get the right match.
If your speedometer is off, it would be a good time to replace the speedometer cable gear with the right set of teeth too.
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