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I have a 1996 F250 with the 7.3L PSD with 202,000 miles that is having some intermittent transmission issues and usually show up under load. The pickup has a new VSS as well as a rebuilt PSOM, speedometer and cruise work as they should. Also, all brake lights have been checked including the 3rd brake light, all are functioning properly and are incandescent bulbs. The code I pulled was P1728 and has since been cleared and has not returned. The fluid was changed around 20,000 miles ago with a new filter and I installed a remanufactured solenoid pack which I don't think was great quality. The pack passed the in the lower end (20.5-21.5 ohm) of the specified range between all pin point tests. I already ordered a remanufactured Sonnax Solenoid pack since the current pack did not hold any air (less than 5 psi) on the ball seats and seemed to leak to the bottom of the solenoid body. The issue I am having is in third gear there is pulsing when the torque converter is locking but once it is locked it seems to hold well. When going into a 4th gear shift on its own there is approx. a 50 RPM flair then the converter locks and it seems good to go. If i manually shift it into 4th gear by using the OD OFF button it seems to shift like it should with minimal flair. The trans does not get hot, 180-190 deg F is about as warm as it's ever been. When code was thrown I was going up hill with a one sled on the sled deck and the trans temp was around 140 deg F with a 20 deg F ambient temp, but rose to 165 deg F and never went much above that. I have been using a Snap-On brick scanner to monitor and all solenoids seem to be commanded on and off when they should, although the torque converter solenoid stays on when brake is pressed, but the converter is unlocking as seen on RPM gauge. I inspected the torque converter for signs of heat and did not see any discoloration or bluing. Fluid is darker than I would've expected but magnet had minimal material. I can't figure out if the torque converter apply piston is cracked or what exactly I have going on. The torque converter was upgraded previous to my purchase back in 2012 but I don't have paperwork as to what it was. Trying to decide if I should order a new converter or what the next diagnosis step is or if a rebuild is imminent. Any help is appreciated.
EDIT: The solenoid pack connector had trans fluid inside.
Thank you,
Blair Code Scanned Torque Converter/ No obvious bluing Bottom of Pan Fluid Oil Drained from T/C Towel sample of T/C Oil
Last edited by rex307; Mar 5, 2025 at 09:06 AM.
Reason: Add cicumstance
The converter should not fair when engaging. I suspect the converter clutch is worn out. 200k behind a diesel, I would be worn out too.
When you pull the transmission to replace the converter, should you go through the transmissions? I would not even hesitate and say yes. With the 96, you should have most, if not all the good stuff, and it should be minimal.
When going from 3rd to 4th it shows the TCC solenoid is controlled ON the entire time using the scan tool. It started the shift flair problem a couple of years ago I just don't drive it enough for it to be a real problem, but I noticed it is getting worse. Before it started doing this it made the 3rd to 4th shift like it should with no shift flair.
@FORDF250HDXLT Thank you for the reply and the great write up. I have purchased a replacement solenoid pack from Sonnax. The male plug is in good condition with no wires showing, but will need to be cleaned of the transfluid inside the plug. Do you think I should just replace the converter while I'm working on this issue. I have not removed the trans yet.
You could still have a failing converter, but since the trans doesn't have to be pulled to replace the pack and you know it's seal has failed, I would simply replace the known bad part first, and see how the trans works then.
