I have a vibration at 70 miles per hour

TCC Torque Converter Clutch switch may be bad and the torque converter may be going out. Does it vibrate or shimmy at 60 + ?

I don't think we are quite understanding the problem. Have someone drive it and determine what is wrong. You cannot disconnect the TC without removing the trans and I guess this isn't what you mean?

IF you have rear wheel drive then check the u-joints for wear/loose. Check slip joint for wear . Check rear engine mount is in good condition. Check wheel balancing

You have it backwards

What you hear is engine noise from
higher rpm, because your trans is not
upshifting, as a result of your input on
the gas pedal

You need to have a trans or repair shop find out why
you have a delayed or no shift condition

When you get to 4th or 5th gear (overdrive) you also
get torque converter lock-up & things should get quieter

catalytic converter part is part of the exhaust system, torque converter part of transmission.if catalytic plugged car will only go 10 miles and hour, if you have torque converter problems car will stall out when you drive 30 miles and hour, when transmission goes in over drive, torque converter lock up.when you apply brakes torque converter suppose to unlock if not car will stall out when you come to a stop.

check the axle shaft assy,an excessive joint angle due to incorrect toe-in or trim height,,,,,Wm or damage inboared or out boared joint,,,,,,,A sticking spider ( tri pot joint)

Let me see know at 45 miles per hour a vehicle usually shifts gears into the highest gear so could it be the torque converter hanging up and not shifting quick enough or maybe its the U joints. Have the transmission fluid checked for proper level and color.
Here's a small test for you when your accelerating up to 55 miles per hour try letting off the pedal at 44 miles per hour and then reaccelerating up to the 55 mph and tell me if it`s smoother if it is then chances are that it`s hang up on third gear. There's also a electric sensor located on transmission that assist shifting it`s usually controlled by the engine timing.
One more thing did the repair man check to see if the tires where directional tires if there not put on right it could cause vibration and early wear out .Hope i helped you.

how many miles, have the U joints been checked? they can cause this if worn excessively

It will be one of 2 things. It is either the lock up torque converter or a coil pack miss-fire.
You can tell if it is the lock up torque converter by lightly applying brakes with your other foot during the concern. If it goes away then it is the lock up torque converter. If it hasn't been doing this for to long then servicing it and putting an additive in it usually corrects it. However it takes about 75 to 100 miles to do so. If that doesn't cure it you will have to replace the torque converter and depending on how it looks maybe the stator support and the TCC solenoid.
If it is a miss fire then it will probably show up under mode 6 data on a scan tool and replacing that spark plug and coil pack should remedy that.

its going to be in the alignment...have the front end realigned