5R55S Hard Shifts


New member
I bought a 2003 LS V-8 sport with 19,000 original one owner miles. The car shifted with a distinct thud when going slow and hard engagement when accelerating. This was only happening when shifting from 3-4 or 4-3 auto mode or select shift mode made no difference. Reverse was somewhat harsh as well. Going from drive to reverse was not nearly as bad as park to reverse. Six transmission shops wanted to rebuild the transmission but I resisted. It ran fine but I wanted to update the car for daily use. I replaced the following with new ford parts: 8 new coil packs, plugs and a TPS. I then turned attention to the shifting problem. Nobody was willing to hook up pressure gauges and everyone used their scan tools. All the transmission shops said the problem was internal. I read up plenty on these finicky devils and worked with a local guy I trusted but did not rebuild transmissions. I pulled the valve body and rebuilt it.... exact same issue remained. We thought it was electrical. All the testing appeared to show the solenoid pack was ok. We tried a new one.... no change... The pcm had remanufactured sticker on it and we decided to send it back to the rebuilder for testing it was “good” no change in shifting. We never saw any codes thrown and found any shorts or bad sensors. After trying the pcm again, we saw no change. It was reflashed at Ford. I read that several updates were done to the pcm so I ordered one off eBay. I installed it and shifting went crazy and that hard thud in 3-4 4-3 remained. The Ford dealer said this computer was fine too, we then tried a brand new ford solenoid pack no change! At this point it shifted horrible and line pressures were all over the board according to the scan tool. I reworked the valve body again with no change. Originally I put in a kit that was suppose to fix lousy and hard shifting and this time I reversed it. I then went to a small local transmission and he tested it with the high end scanner. Nothing appeared wrong. We put the original pcm back in which Ford also said was good, original solenoid pack and had the original problem of reverse harsh hard-4 to 3 and 3-4 with a thud and hard engagement. Adjusting the bands Helped for 10 minutes! Ultimately the trans shop felt the servo bore was worn and we rebuilt it. This did nothing. We had the exact same issues! I then suggested we put a newly rebuilt pcm in it. Voila!!!! Fixed!!! I learned the hard way that the local ford dealer cannot diagnose- numerous shops want to throw transmissions at these and a long hard road lead us back to the computer that I was told by ford was good and no tranny shops saw any issues with it in their scanners! I know servo bores cause problems but at 19k miles? This car had a rebuilt transmission put in by ford at 259 miles! A new valve body in less than two years of the cars life, a rebuilt pcm all before I got it in 2018! I’m guessing Ford chased this problem and Miss diagnosed it the whole time it was under warranty!!! I hope this helps anyone that is struggling to get their LS or other vehicle with this Transmission running! They say tap the pcm and see if pressures chsnge but mine were not reading high ever! Good luck!!!