Yep! A very useful troubleshooting technique - use your voltmeter in parallell with the cables to the starter (check both sides of the circuit) while a buddy cranks the engine over. You are looking for significant voltage drop, the clamp can be fine but corrosion on the wire interface will hork the current draw. Also, see what the current draw is while cranking the starter itself - the voltage at the battery terminals themselves should not drop below 9.5 volts, say.
If the Truck has sat for a long time, corrosion at the various electrical grounds will do exactly what you describe. Also, check for loose connections - hot or smoking wires when this happens.
If the starter itself is bad, it will draw excessive current, rebuilds are hit and miss and even if they work, they generally don't seem to last very long sometimes. Note too, starters have a rated duty cycle, When an engine is tuned properly the starter is engaged for just a split-second. If the engine does not start right away, the starter windings become extremely hot and need a half an hour or so cool down before it is safe to try again. Hardly anybody knows this, and even fewer follow the spec. But unless you feel like shelling out the dough and replacing another starter, until you fix the underlying, take it easy on your starter, 15 seconds of starter grinding, better go get lunch. It would also save your battery if you had an outboard charger to top that off too. Let us know what you find! Tedster
Cleaning all the grounds and SAE connectors with solvent and then treating with a good electrical grease like NO-OX-ID pays dividends. The voltage drop on old, corroded connections can be significant.