transmission help needed bad

1990 lincoln continental 3.8 i have put alot of work in this car and now my trans is acting up everytime i hit 18 mph i got to let off the gas just a little to get it to change gears and i have to do that again at 34mph to change gears.The trans does not slip or lag at all until i hit those speeds.I flushed the trans and put some slick 50 in there but it still does it do you think i need to rebuild it ive been quoted at 1100 bucks by a mechanic

I feel your pain, I had a 91 Cont. that the trans. went out at 109,000 miles this cost me $1800. This year I also purchased a 90 Cont. with a bad trans. because I had a good tran in a 89. To make a long story short I pulled the tran myself and it was so bad I paid a freind $400 at a shop to put it back in for me.
So ask yourself the question will it be a good car after a rebuilt trans? The price $1100 is reasonable.
From what I have seen most all Cont. have trans. problems between 105,000 and 120,000. Also the waterpump goes and blows a headgasket on the 3.8's. I like the cars and like the ride but so many problems so after my 4th Cont. I am back to the Cady's, much less problems.
By the way the only trans that you canuse in our car are the 89 and 90 years.

Oh yeah i see i am not the only one here i have done so much work on this car it feels like a son to me lol i have replaced the motor and just about everything else i have just put new motor mounts on there and me back is still killin me it is now my trans that is goin haywire the car takes off fine just when i hit those speeds i have to let off gas for it to change gears ive been told to change the speed sensor but i dont know where that is or if that will solve the problem but thank you for advice its a choice ill have to make thank you

beegolden You are right on . I have 92 Lincoln water pump blew 110000. Head gasket shot. I think it is A weak spot. How did you torque head bolts@ get the degrees this ford book gives.Ringo7