Cause:
The non-anodized valves score and seize in the bore
Correction:
These valves are hard anodized with annular grooves which eliminate surface wear and reduce valve hang-up.
GM 4T60-E and 4T65-E shift valves have changed materials over the years, starting with steel, changing to silver-colored uncoated raw aluminum, and finally anodized aluminum. These units can have a combination of these materials with the silver-colored uncoated raw aluminum being especially problematic due to scoring/scratching and intermittent sticking. The Sonnax 4-3 manual downshift valve eliminates surface wear and reduces valve hang up.
n 4T60-E units, fits '91-later units only.
Symptoms:
Cause: The non-anodized valves score and seize in the bore
Correction: These valves are hard anodized with annular grooves which eliminate surface wear and reduce valve hang-up.
GM 4T60-E and 4T65-E shift valves have changed materials over the years, starting with steel, changing to silver-colored uncoated raw aluminum, and finally anodized aluminum. These units can have a combination of these materials with the silver-colored uncoated raw aluminum being especially problematic due to scoring/scratching and intermittent sticking. The Sonnax 4-3 manual downshift valve eliminates surface wear and reduces valve hang up.
SONNAX Installation Instructions