75 K10 No Speedometer-NP203

[rich weyand]

OK, follow along. Inside the NP203 is a speedometer driven gear. I have seen them with 18 and 22 teeth, stamped "H" and "M" respectively. The driven gear has a square hole in the end that is a mate for a speedometer cable. This is a heavy duty steel part and is very unlikely to be a problem. They are also hard to find.

The driven gear is retained in place by a threaded sleeve with an internal O-ring oil seal. Part number is AC DELCO #326561, and is easy to find. This sleeve is threaded to accept a speedometer cable.

Onto the sleeve is mounted a ratio adapter. This adapter ratios run from.73 to 1.36, and there's a bunch of them. This corrects for axle ratio and tire size. The part number varies with ratio, as the ratio is built in to the part.

Onto the ratio adapter is mounted the speedometer cable.

The ratio adapter and the NP203 driven gear are both females: there is a "key" that connects them. The correct key is HR124. On the other side of the ratio adapter, the ratio adapter is female and the speedo cable is male, but not the same. The adapter you need is HM146. You get them here: http://www.texasindustrialelectric.c...on_Adapter.asp. No internet ordering, you call them on the phone. They're like $10 for the pair.

If you know what the axle ratio and tire diameter is, I can figure out the right ratio and give you the part number. Or just give me the ratio (stamped on the adapter) and I'll look up the part number if he wants an exact replacement.