A TSB on this:
TSB 88-16 (Mar)
SUBJECT: GM TRANSMISSIONS
PROBLEM: No upshift
CAUSE:
May be caused by imprex material lodged in a seat or under a ball in the governor. Imprex material is used to seal transaxle cases against porosity and has the appearance of RTV sealer. This material can prevent the governor balls from seating properly, or can plug the feed passage and result in low governor pressure.
CURE:
If it is suspected that imprex material has migrated into the governor, remove the governor from the transaxle. Reinstall the governor cover without the governor. Start the engine and shift transaxle to drive for approximately 5 minutes. This will flush out the governor oil passages.
Clean the governor and check for proper seating of the governor balls. Hold the weights outward against the bails and pour solvent into the governor shaft. If solvent leaks past the balls, replace the governor. If no leakage is found, reinstall the governor and verify operation.
And just a general checklist for a "1st gear only" condition:
1st Speed Only No 1-2 Shift
1. Governor valve may be sticking.
2. Driven gear in governor assembly loose, worn or damaged.
3. The 1-2 shift valve in control valve assembly stuck closed. Check governor feed channels for blocks, leaks, and position. Also check control valve body gaskets for leaks and damage.
4. Intermediate clutch plug in case may be leaking or blown out.
5. Check for porosity between channels and for blocked governor feed channels in case.
6. Check intermediate clutch for proper operation.
