I know experienced mechanics who won’t tackle a job like this.
Since you are likely the only person who has ever done this, the best you can hope for is specific answers to the opposite question - how to convert this car from automatic to manual, which will, of course, answer your questions. The ideal would be to find someone who wants to convert the opposite direction and swap parts.
As tester pointed out, the first obstacle will be finding/programming a computer that is programmed for your engine mods and for an automatic transmission. Computer swaps can get complicated, particularly if your model car has theft deterrent system. The engine computer must sync with the immobilizer which must sync with all your keys, etc. If the pinout on the computer plug is not identical for automatic and manual models, you will have to re-wire the plug for the computer. If the computer sees anything electronic that does not belong on an automatic, it will likely crash or go into limp mode, or at least will illuminate the check engine light.
The next problem is downshifting properly when you floor it (i.e. passing gear controls) unless you will operate in manual mode at all times. If this model car uses drive-by-wire throttle, the engine computer may handle that problem for you. Otherwise, that will be either a cable or a vacuum system or an electronic control that must come from the donor car.
The next problem is getting a rear end that will keep the engine working in the RPM range that your engine is designed/tuned for. You will likely need a drive shaft and hangar for an automatic, but that will be easy.
There will be a lot of little electronic mods that you have to do, like putting jumpers on the wires that currently connect to the switches on your clutch pedal that keep the car from starting until you depress the clutch and disable the cruise control when you press the clutch. Similarly, you will probably disable the ignition key lock on your automatic shiftier rather than bothering to get that working.
Good luck. I have gone down roads like this before, and there is a reason why most of the advice you will get is - change cars.
On some of my Toyota forums, the drag racing guys like to use GM 350 TH transmissions with adapter plates. These transmissions are readily available, can handle lots of power, and don’t need sensors or a TCM. And are cheap to rebuild.
You might consider buying a Z with auto trans and transferring the parts from your current car to it. Given that installing an AT in your car is a monumental task, this might be a little easier.
Take it to a speed shop and tell them what you want. After they get done staring incredulously at you, they’ll charge you a lot of money and do the work.
If you don’t already know what you need to do or have access to people who do, then you can afford all the parts you want but you won’t be able to get the job done.
MOST people convert from Auto to Manual… I wont go into the typical reasons for this but the most important reason this is the way to go is because the Auto version has all the optional transmission equipment already there… When you change to a manual its basically trimming Down all the electronics and hardware rather than building it up and or hoping they used only one type of wire harness that can accomodate both types of transmissions.
NOBODY goes from manual to Auto… Too many reasons why… Just buy the Auto version of the same car.
It would be pretty easy to sell your manual…being a performance car…most buyers want the manual anyway.
If the reason to keep the car is all the high-po mods, then buy an AT car, swap out the neat parts, sell the MT car, you’re done.
If you have to ask, you can’t afford it. Agree, sell and buy another with an automatic
In the 1920’s, there was a story of a rich man who went out shopping for a yacht. He found one he liked and asked the salesman how much it cost.
The salesman responded, “But, sir, if you must ask how much it costs, you can’t afford one.”
When I first heard that story many years ago, I thought it was a case of a smart-alecky, arrogant salesman. Later, I learned it was true. Yachts were so horribly extremely unbelievably expensive that the only people who could afford them were the people so rich they knew they could afford anything they wanted. And, literally did not need to ask what something cost if they wanted it.
These were people who, when my dad was working for a dollar or two a day, would have a birthday party for a kid and spend a hundred thousand dollars on it.
ASEMASTER had the best advise buy a wrecked auto and use it as a parts car. This is going to take a significant amount of work if the trans is computer controlled.
I believe the best advice given was to sell this car and buy another Z that came from the factory with an automatic transmission
Money not being a factor here buying a second car for parts or to accept the modified engine is the best way to go.
NOBODY goes from manual to Auto…
Perhaps with a late model sports car but I have seen a number of 1960s and '70s cars converted from 4-speed to automatic for the drag strip.
"But, sir, if you must ask how much it costs, you can't afford one."
I had a guy pull that on me once. “Well how the hell am I supposed to pay you if you don’t tell me how much to give you?”
My version is “If you have to ask how to do an EXTREMELY complex mechanical task, you can’t.”
I’ve done this conversion many times in the past and auto to manual as well. That was in the days before vehicle computers and parts were very cheap back then. Today…I wouldn’t even attempt this sort of thing. Your best course of action is to sell your manual Z and buy one that’s an automatic.
Re: Nobody goes from manual to automatic …
I wouldn’t myself. But for some reason folks who like to restore older Ford trucks … trucks in the “classic” category … some of them during the restore switch the truck from the original manual to a C4 or C6 automatic.
Antiques, classics, not a real problem. Modern cars? REAL problems.