* TV Cable Adjustment (Most Likely): The Throttle Valve (TV) cable connects the throttle to the transmission. It tells the transmission when to shift. Incorrect adjustment is the most common cause of shifting problems, especially being stuck in a lower gear. It needs to be precisely adjusted to match the transmission's specifications.
* TV Cable Linkage: Check the cable itself for damage, kinks, or binding. Make sure the cable is properly seated and moving freely at both ends.
* Transmission Control Module (TCM) or PCM (Powertrain Control Module): These computer modules control the transmission's shifting. A faulty sensor, a wiring problem, or a malfunctioning TCM/PCM could be preventing the proper shift commands from being sent. A diagnostic scan is crucial here.
* Shift Linkage (Less Likely, but Possible): If the transmission is a manual (highly unlikely on a 1992 Imperial), there's a shift linkage that could be adjusted incorrectly or broken. However, it sounds more like an automatic.
* Governor: This is a mechanical device inside the transmission that helps determine shift points. Though less probable given the new transmission, a faulty governor could cause issues.
* Fluid Level and Type: While you have a new transmission, double-check the fluid level and type. Using the wrong fluid can cause problems.
* Valve Body (Transmission Internal): If all else fails, there could be a problem *within* the new transmission's valve body. This is less likely given its newness, but a manufacturing defect or damage during installation are still possibilities.
What to do:
1. Check the TV cable adjustment FIRST. There should be a specification in your repair manual or online for your specific model. Adjust the cable according to these instructions.
2. Inspect the TV cable and linkage for damage.
3. Get a diagnostic scan: This is absolutely essential. A scan will read codes from the TCM/PCM and pinpoint the problem. An auto parts store often offers free code reading.
4. Check the transmission fluid level and type.
5. If all else fails, return to the installer: If you had the transmission professionally installed, contact the installer immediately. They may have a warranty and should troubleshoot the issue.
Ignoring the diagnostic scan is a waste of time and money. Getting a professional opinion early on can save you from unnecessary repairs and expenses. The problem almost certainly lies in the *control* of the transmission, not within the transmission itself, given its recent replacement.
