Transmission Failure, P0720 Code Need Help

[Criss]

2008 Ford F150 XL 2wd, 5.4L, 4R75W Trans (I think). Is my dads truck. Went to leave the house one one day a few weeks ago, had to give it a abnormal amount of gas for it to move but finally went and was okay till the drive home. CEL came on with a "reduced engine power" & "transmission failure" message on the message center. Pulled codes, had a P0720 (output shaft speed censor circuit) code. After code and failure message, truck still has reverse, but has no Drive, 2nd or 1st gear, will not go regardless of rpm. Changed OSS, and OSS connector and inspected harness. All good, and CEL went off. Truck would drive in all gears, but still was correct. At times it felt like it would slip out of gear, or take alot of rpm to go into any gear. Now it's back to having no Drive, 2nd, or 1st forward gears. Reverse still perfect. BUT, I'm stumped now because even after it was "fixed", and it's back to having no forwards gears, there's no check engine light, no messages on the message center. I have no codes to read to figure out the next step to take to repair. We changed the Transmission Range Sensor, with no change. Only thing left to change would be Turbine/Input shaft speed sensor. That's our next step in a week or 2. Other than that, I'm at a loss.... Any info would be greatly appreciated it, and if I left anything out please let me know. Thank you.

 

[Fellro]

While it may well be electrical, it very well could also be a hydraulic/clutch issue. What does the transmission fluid look/smell like? Have you checked the fluid level?

 

[Criss]

Yes, before we changed the OSS and connector I checked fluid. After installing the sensor and going for a ride for a bit, once we got home double checked it again. Level look good and normal in operating range, smelt good and looked cleaned. Both ends of the speed sensors are magnets of course, they had trans fluid on them but no shavings or chunks. Someone suggested it may be forwards drum has went now. Some quick research and I've found they are some sort of weak spot with a snap ring and such. But not sure. And thanks for the reply!

 

[Fellro]

Unfortunately, it may well be possible there is a clutch or other hard part failure. I just wanted to get the easy part out of the way. It is amazing how many people overlook those simple things. It does sound like classic forward clutch failure. You most definitely can have working reverse and no forward gears when that happens. However, being an electronic trans, a failed solenoid would act the same way. I am more versed in the old mechanicals.

 

[Criss]

Yeah and I'm the same way and with people I work with, always check the simple stuff. Lol but by now, probably just pull it and take it somewhere, considering I don't know anything about transmissions, to hopefully get it going it again soon. Had an old dodge 2500, that had lost overdrive and went through all kinda stuff, fluid & filter, shift solenoids, od solenoid ect and it didn't get fixed, traded it in about 6 months ago for the Ford and its pretty disheartening for him he's already having trans problems again out of a truck. I appreciate the help and who knows I may try a couple more things 1st

 

[d-kuzmen]

Sounds like you lost the forward clutch. Gonna have to come apart.