Hi, I am helping a friend out with his 2000 F-250 5.4L truck. It delays shifting up then shifts hard and has unexpected downshifts. He has had the transmission rebuilt three times. He has taken it to a Ford dealer and they have confirmed nothing wrong with the PCM or the transmission. He has had the rear diff speed sensor replaced twice with a Motocraft sensor. Nothing has worked and he is really fed up with it. It's been in the shop for weeks on end and cost him thousands to no avail. The problem only happens when fully warmed up. No transmission error codes. No flashing OD light.

I captured some charts using FORscan while he was driving and I wondered if any kind members had some helpful input.

Every hard delayed upshift was represented as a spike on the "torque converter slip actual". Do you think this is significant, perhaps indication of the TC being the problem or just another symptom? See the orange line below. The spike is about the 49.69 timing point. From top to bottom this is:

OSS - Output Shaft Speed.
RPM - Engine Revolutions Per Minute
TSS - Turbine Shaft Speed
SSA/SS1 - Shift Solenoid 1
SSB/SS2 - Shift Solenoid 2
TCC - Torque Converter Clutch Solenoid
TCC_F - Torque Converter Clutch Fault
TC_SLIPACT - Torque converter slip actual
TR - Transmission range



This chart shows what happened with the unexpected downshift. The light blue line is the actual torque converter slip and the dark blue line is the demanded torque converter slip. During the downshift the demand for slip dropped but nothing happened with the actual slip. Is this normal or expected?

From top to bottom this is:

TCC - Torque Converter Clutch Solenoid
TCC_F - Torque Converter Clutch Fault
TC_SLIPACT - Torque converter slip actual
TR - Transmission range
TR_F - Transmission Range status
TC_SLIPDSD - Torque converter slip desired
TORQUE - Net Engine Torque



What other parameters can I chart to try to diagnose this problem?

We have a new Ford TSS sensor in hand but I am not seeing anything weird with the waveform on the charts so I am thinking it isn't worth the hassle to install it.

Thanks!!

 

You need to see what vehicle speed and throttle position are doing. The shifts are scheduled mainly from those two parameters. If either one has an issue the shifts will do what you're describing.

 

Thanks. I will check that.

Also getting error C1229 which it seems is related to the VSS. I've only just learned this so maybe that is a clue to the transmission problems?

Where is a good place to purchase and download a PDF of the factory workshop manual for this truck?

Thanks.