Early or Slipping 3-4 Upshift

1. Improper fluid level.
2. Damaged or improperly adjusted linkage.
3. Low main control pressure to overdrive band servo.
4. Sticking or dirty valve body.
5. Burnt overdrive band assembly.
6. Damaged or glazed reverse clutch drum or overdrive band.
7. Worn governor seal ring or counterbore in case.