2006 ford f150 fx4 5.4l 4r70w
Had my transmission rebuilt and installed by a transmission mechanic. Test drive not good. Put in drive truck doesn't move same if I manually 1st 2nd. Engine just revs and then will grab a gear. Once moving shifts fine come to a stop and falls out of gear. Mechanic told me it has to be electrical. So I replaced cpu, hard wire, solenoid,speed sensor. I keep getting a code for the speed sensor but it is new 2 times. I'm lost.

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I would find a new mechanic or bring it to Ford.

I hate to say it, but there are times when it's actually cheaper to bring it to Ford. Just because they have the knowledge and experience.

 

I installed a new MLP switch, No change.

 

I'm thinking both of you are past keyboard jockey level diagnostics. It's just incredibly hard to diagnose long distance with no real data to work from. We can't drive the vehicle to feel, firsthand, whats happening or not nor hook anything up to them to see what the data tells us.

D

 

Figured out the Direct Drive drum had all the teeth stripped off - where it slides onto the output shaft teeth.
At first I thought is was OD servo leaking and direct drive clutch plates worn down.
But I realized the transmission failure was instantaneous, not gradually more slipping.
Looked closer and noticed no teeth on the inner bore of the Direct Drive drum that contains the 3rd gear clutches.

Now with a new Direct Drive drum a Sonnax Zip Kit, all new clutches and seals, and most of the bushings replaced - All works great.
Yes I rebuilt it myself; after watching the Transmission Bench you Tube videos - and ordering the master rebuild kit.