* Low or Incorrect Fluid Level: This is the simplest and cheapest thing to check first. Ensure the transmission fluid level is correct when the transmission is at operating temperature (check the dipstick after driving for 20-30 minutes). Low fluid, especially when cold, can cause shifting problems. Also, ensure the correct type of ATF is used (consult your owner's manual).
* Fluid Viscosity: The wrong type of ATF, or ATF that's degraded, can thicken significantly when cold, leading to sluggish shifting. Even if the correct type was used initially, it's possible it's degraded. A fluid and filter change with the correct type is warranted.
* Valve Body Problems: The valve body controls shift scheduling. Problems within the valve body (worn or sticking valves, incorrect valve body assembly during the rebuild) can cause the transmission to stay in first gear when cold because the fluid isn't flowing correctly until it warms up and the fluid becomes less viscous. This is a very common cause of A4LD shifting issues.
* Governor Problems: The governor regulates shift speed and timing. A malfunctioning governor, either mechanically sticking or having an issue with its internal components, could prevent proper upshifts when cold.
* Sensor Issues: Various sensors (e.g., temperature sensor) provide input to the transmission's computer. A faulty sensor can cause the transmission to behave erratically. Although less likely to cause *only* a cold-start issue in first gear, it's worth consideration.
* Torque Converter Issues: While less likely, a problem with the torque converter (though rare, it could bind when cold) could contribute.
* Improper Rebuilding: Unfortunately, the rebuild itself might not have been performed correctly. Some potential sources of error might include: Incorrect valve body adjustments, damaged or incorrectly installed components, or the use of inferior parts.
Troubleshooting Steps:
1. Check and correct fluid level and type. This is the absolute first step.
2. Perform a complete fluid and filter change. Use the correct type of ATF specified for your A4LD transmission. Dexron III/Mercon is a common choice, but consult your owner's manual for specifics.
3. Inspect the valve body. This usually requires disassembly. If you're not comfortable with this, take it to a transmission specialist. Look for any signs of wear, damage, or incorrect installation.
4. Check the governor: Access and inspect the governor for any mechanical issues or binding.
5. Scan for trouble codes: Use an OBD-II scanner (if your vehicle is equipped for it; it might not be with a 1990 model year) to check for any transmission-related codes. However, older OBD systems often lack transmission codes, and other diagnostics will be necessary.
Recommendation:
If you're not experienced with automatic transmission repair, it's strongly advised to take your Ranger to a reputable transmission specialist. They possess the tools, expertise, and experience to properly diagnose and repair the problem. Given the transmission has already been rebuilt, pinpointing the exact cause requires a skilled professional. They can perform further testing to identify the specific component causing the cold-start first-gear issue. Continuing to drive it with the problem could cause further damage to the transmission.
