Trans Failsafe and code P1748

[x5drew]

I have a 2001 4.4 X5 with 100,480 miles.
The trans failsafe turning on and the service light.
I read codes with my code reader and got P1748 code i looked it up and found bmw code p1748 Transmission control module self test .

Truck went into Trans Failsafe when driving 60 mph in lite rain everything ran great untill it went into Trans Failsafe. I turn car off and restart and service engine light & trans failsafe turned off and everything runs great then i drive less than one mile and it goes back to trans failsafe mode service light is on and i get P1748 code. I reset it and it goes back to Transfailsafe everytime i reset it after less than a mile i drive.

I also try to turn key on ten seconds turn key off ten seconds then start car it clears service light Trans Failsafe message turn off runs great about a mile the it goes back to trans failsafe mode and service lite turns on I check code and get P1748.

Trans works great when Trans Failsafe mode is off but it wont stay off.
I dont think i have bad a transmission.

Work that i did in last few weeks.
I installed new Valve Cover Gaskets, New Plugs, New Plug Boots, New Coils, new Oil and Filter, new Air Valve, two new Cats and Oxygen Sensors,
Everything works car ran great no codes no service lights for two weeks untill three days ago I had to installed new speed sensor rear passenger side three days ago to clear up the dsc three dash lights that turned on on the dash the new speed sensor turned all three DCS lights off on the dash.

Now trans failsafe problem and code P1748 ?
Any Ideas?

Thanks x5drew