2007 crown victoria police interceptor transmission problems?

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My 2007 crown vic pi has got some serious trani problems, was wondering if i
might be able to use your assistance with knowledge.  Well the first issue
came when i was on my way home and went from 0-110 at about 75%throttle
then layed off and went to accelerate back to 100 from 90 but the car just
revved and didnt want to catch(maxxing rpm/no movement), as i was on my
way home from work and out in nowhere with my phone dead i tried to keep
going and fix the issue later so i tried everything i could.  The only thing that
worked was me turning overdrive(4th) off and matching rpm/speed before it
started to accelerate.  I made it home nevertheless but when i brought it to
my mechanic he said you have a better chance of keeping an eye out for a pi
trani to replace it(costs to find and fix would be equal if not more) and told me
to just ride it smooth with the 3 gears for now.  Well it has been 2 months now
as i cant find a trani for itand cant afford a fix right now going paycheque to
paycheque.  I went to a family wedding 300 km away with it(i know it is
horrible/i drove slow and steady) and on the way back my trani slipped
250km from home so i pulled over restarted it and turned overdrive off waitng
a second and boom it worked, so i continued home and went to bed.  Woke
up the next morning to go run around and it was just revving without
movement even with od off, so i checked the fluids and discovered ere was
no trani fluid(im talking bone dry, i dont know how i made it home) filled the
trani fluid, was moving very slowly until eventually it went into service
mode(wrench popped up) and started working the way it did before(od off) so
drove around made sure it was good, went to bed.  Next day same issue, but
this time effecting my work hours so i got mad and discovered if you do a
burnout the transmission would kick into gear and drive the way it did before.  
Few days went by and it started working normal, the only issue being when i
go into reverse, then back into drive i have to rev above 3000rpm to get the
trani to kick into gear or catch(sounds like a hard shift, brings 3000rpm to the
back tired so sometime a nice squeel is made, i do hold the brake to ensure
safety of others/cars).  I ask nearly everyone i meet that the car catches the
eye for but slim have given good ansers, i believe it could be a multi of things,
such as a slow leak(hoping it is the gasket for filter to replace it), a lockup
solinoid, the speed sensor curicuit or even just old wiring being faulty.  I want
advice from someone reliable and trustworth and found you so i figured i
would ask for some of your time.  Thank you kindly in advance,