2003 Lincoln LS V8 Trans Shifting Problems


New LVC Member
Mar 6, 2023
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I purchased a 2003 LS v8 with 130k miles and a number of issues... the largest being shifting issues. Was told originally it needed the solenoid pack replaced (had codes for all three shift solenoids). I started by replacing the solenoid pack, but it did not fix the problem. I then sent out the PCM to be tested/repaired and it tested okay. The company that tested the pcm noted to looked for bad grounds. I then found the o2 sensor wires were cut and the 4 wires were touching - causing a bad ground (cats were stolen and previous owner had repaired by installing a pipe where the cats were originally w/o replacing o2 sensors). I then made sure the wires could not touch, but still do not have o2 sensors (all circuits are open for sensors and heaters). This got rid of the codes for bad solenoids, but the trans still shifted very poorly. I then replaced the entire valve body with an "upgraded" sonnax reman valve body. This did not make any difference to the shifting.

The 1-2 shift is harsh, 2-3 shift hits hard then the car seems to defuel for a split second then take off again, the 3-4 shift is slow and has a bit of shudder, 4-5 has no issues.

The car obviously has codes on for the o2 sensors/cats missing, but no other codes on the pcm. I was planning to replace these once the shifting issues were resolved, but is it possible that these open circuits could be causing poor shifting? The only other common problem I have read about for these transmissions is the servo bores wearing out, but I thought that the worn out bores would result in losing gears?

Any other possible causes? I have read that even the coil packs could cause poor shifting, but this seems extreme to be caused by any type of misfire.

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