Q: What are the differences between the Throttle valve cable and detent cable on Buick Century?
A: On all transmissions except the THM-250, THM-350, and THM-400 models, a Throttle Cable controls hydraulic pressures, shift points, shift feel, and downshifting, while the THM-250 and THM-350 utilize a detent cable, and the THM-400 employs an electrical detent switch, which requires separate adjustment. Although the detent cable resembles the Throttle Cable, it solely manages downshift functions, with the distinction in terminology reflecting their different roles rather than their designs. Prior to making adjustments, determine the cable type in your vehicle, either Type One or Type Two. The Type One Cable features a snap-lock assembly integrated with the cable, located next to the cable mounting bracket at the engine, which should be in the locked position for adjustment. The Type Two cable has a different locking mechanism, also positioned similarly, with a lock tab that is set when released and adjusted when pushed downward; earlier models from 1981 can be identified by a visible spring beneath the lock tab, which is absent in 1982 and later assemblies. For Type One, first remove the engine air cleaner assembly, then push up on the bottom of the snap-lock at the cable bracket to ensure the cable can slide freely. Next, move the carburetor lever to the wide open throttle position and hold it there, push the snap-lock flush, and allow the lever to return to the closed position. If this adjustment does not resolve issues with late shifting or lack of part throttle downshift, a qualified mechanic should conduct a transmission fluid pressure test.