* Incorrect parts during rebuild: This is the most likely culprit. The wrong gears, planetary carrier, or other internal components could have been installed during the rebuild. This is especially possible if the shop wasn't using OEM parts or lacked proper expertise.
* Internal damage during or after the rebuild: Something could have been damaged during the reassembly process (a bent shift fork, damaged gear teeth, etc.). Alternatively, debris from the rebuild process might remain in the transmission causing issues. Driving after the rebuild with a low fluid level could also cause further damage.
* Valve body issues: While less likely given a recent rebuild, problems within the valve body could be causing incorrect shifting, leading to the code. A faulty valve or solenoid could be preventing proper engagement of third gear. This is often overlooked but important if the rebuild only focused on the mechanical components.
* Low or contaminated transmission fluid: Check and change the transmission fluid (even if it was recently done). Low fluid or contaminated fluid will cause significant damage, even in a newly rebuilt transmission.
* Wiring or sensor problem (less likely): Though less probable after a rebuild, a wiring harness problem or a faulty sensor could cause the TCM to incorrectly report the gear ratio. This is less likely but worth investigating if mechanical issues are ruled out.
Troubleshooting Steps:
1. Fluid Check: Immediately check the transmission fluid level and condition. Low or dirty fluid necessitates a drain and refill *at minimum*.
2. Professional Inspection: Given the recent rebuild, return to the shop that performed the work. They bear responsibility for ensuring a functional transmission. They should have the diagnostic tools and expertise to pinpoint the problem. If the warranty has expired, unfortunately, you'll have to pay for a diagnosis.
3. Get a Second Opinion: If you're unsure of the original shop's diagnosis or capability, take it to another reputable transmission specialist for a second opinion. This can help rule out potential bias.
The P0733 code points to a significant internal transmission issue. Ignoring it will lead to further damage and potentially a complete transmission failure. Prompt professional attention is crucial.
