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4R100 issues no forward gears

19K views 4 replies 5 participants last post by  matthewd11  
#1 ·
Hey everyone I'm new to the forum and I am wondering if anyone could guide me in the right direction on the issues I'm having. Its a 99.5 F350 4WD. Anyway a couple weeks back i replaced the neutral safety switch and harness due to a corroded prong and all was well until yesterday. I was cruising along no issues stopped at a red light it turned green i hit gas pedal just revved. Only reverse would work.

So I did some scouting around, made sure the neutral safety switch had not settled or something like that and proceeded to check on the three bolts under the valve body plates to see if they were loose because I read that could cause a loss of pressure ect ect. They were tight and I am stuck and don't know what I should do next I have the whole bottom of the tranny disassembled. Also I dunno how long the current fluid was in there I bought this truck 6 months ago. It has 126,000 miles and until this occurrence all seemed well. shifted perfectly, no slipping. The magnet in the bottom of the pan had some debris, mostly the really fine particles, but there were 7 or 8 metal fragments you could feel, but from other pics ive seen not terrible. The tranny fluid was quite dark too.

So before I take this truck into the dealership any suggestions as to what could cause this? Electrical issues? sensors? I just fail to see how it could go from absolutely flawless, to complete failure, especially without my tranny pan being riddled with debris.
 
#2 ·
IT’S NOT AN ELECTRICAL ISSUE, HAS TO BE MECHANICAL. DID YOU TRY PUTTING IT IN MANUAL LOW ? IF IT MOVES THERE THEN THE PROBLEM IS WITH THE O/D ONE-WAY CLUTCH, IF IT STILL DOESN’T MOVE IT COULD BE THE FORWARD CLUTCH OR THE LOW ONE-WAY CLUTCH ISN’T HOLDING. COULD ALSO BE STRIPED SPLINES IN THE FORWARD PLANETARY.
 
#4 ·
I just fail to see how it could go from absolutely flawless, to complete failure, especially without my tranny pan being riddled with debris.
Something mechanical broke inside the trans. Many things can break in two and you're not going anywhere, and won't put ANY debris in the pan. We can guess all day as to what broke, but the bottom line is that to fix whatever it is the trans needs to come out and be rebuilt or replaced.