Changing an Automatic to a ManualLast Updated October 6, 2023 | Meghan Drummond
Converting a vehicle with an automatic transmission to a manual is usually not particularly cost-effective, nor is it particularly easy. But sometimes, it’s simply the only way. If there’s a car you have your eye on that’s very rare, you may only get a chance to buy an automatic transmission variant. Or if it’s a car that only comes with an automatic transmission and you really want to row your own gears, you may need to perform a transmission swap.
Essentially, if you’re just thinking about buying an inexpensive automatic sedan that’s fairly run-of-the-mill and converting it to a manual, that’s probably not a great idea and you’d be better served in terms of time and money to wait to buy a manual when it became available.
For those who don’t have other options though, swapping out transmissions is definitely possible.
Automatic and Manual Transmission Differences
An automatic transmission has many more differences from a manual transmission than you might expect. Many people expect the base components of an automatic transmission to be the same, only with some extra mechanics to change gears when needed and without a clutch pedal. Unfortunately, this isn’t the case.
Automatic and manual transmissions both require a coupling device, a piece of equipment that is used to connect and disconnect the transmission and the engine as needed. In a manual transmission, that piece is called a clutch, and in an automatic transmission, it’s a torque converter. In order to swap your automatic transmission for a manual (or vice versa if that’s your objective), you’ll need to disconnect the current coupling material and install the new one. There will also be entirely new pedal assemblies that are required, and, of course, the shifter and connecting components.
Finding New or Used Parts for Transmission Swap
A Donor Car
Though it’s easy to predict some things that you’ll need, other parts tend to be surprises. In order to deal with these parts, people will sometimes purchase what’s known as a donor car and strip it down in order to get the components that they need that are year specific. The trouble with this is that you’re essentially doing twice the work, and you’re doing it at the same time.
Very few people have a garage large enough to accommodate this process. Ultimately, it is one of the less expensive options, but it also means that you may be getting parts of questionable quality.
The benefits of using a donor car are that they typically are had for very little money, and depending on the parts you strip off, you may be able to sell some to recoup some of the cost.
Piece by Piece
On the other hand, it’s possible to piecemeal a new driveline simply by purchasing high quality used parts. You can find these through a junkyard, a local mechanic, or even through an online site like eBay. These tend to be a little more of a sure thing than getting your parts out of a donor car, but it does also tend to be more expensive (though admittedly in small bursts, so if your plan is to buy pieces over a long period of time, this may be less to bite off at once), and you need to research to ensure that all the components that you’re purchasing are capable of working together. Sometimes car manufacturers make small, not particularly well-advertised, changes to things as small as the bolt on a pedal assembly and suddenly you’re scrambling to find a fix.
The route that guarantees the most in terms of reliability is not coincidentally a little more expensive. Buying new parts usually confers some type of warranty or guarantee of quality as well, and typically brands really believe in their product and will work with you to make sure that you’re satisfied with the overall results.
There’s no reason to stick to one route or the other. As long as the parts you purchase are compatible with each other, it won’t matter if one part is new and another is old.
With regards to compatibility, one of the easiest things you can do that will help your transmission swap be successful is simply to buy the manual transmission that was designed for the model car that you’re working with. This obviously isn’t an option if there wasn’t a manual option, but for most cars, you can find a manual transmission that was designed to fit in the body of your car. The nice thing about that is that most of the hoses and connections will be approximately the same length, resulting in fewer new parts and minor inconveniences for you.
In order to install a manual transmission into a car that currently has an automatic, you’ll also need a new clutch, flywheel, shift assembly, and pedal assembly. Unfortunately, even the brake pedal of your existing pedal assembly isn’t compatible and will need to be replaced. You’ll also likely need a host of smaller components depending on the scope of the project.
If you’ve already committed to changing the transmission then it’s a good time to evaluate changing the engine as well. This makes the transmission swap a little bit simpler and for older cars is generally a good investment anyway since it’s likely that the engine has a good number of miles on it.
This is entirely up to you, but since you’re going through the effort of making a transmission “speak” to an engine, you may want to make sure that you’re doing the work for an engine that’s going to last for a long time. It’s a good time to install additional modifications as well, like a short throw shifter, or a new exhaust system. There are a lot of other upgrades that can be done at the same time without adding a lot of additional work since you’ll be moving around so many things anyway.
Unfortunately, even with the best list we can give you, there’s no way to completely be sure of every part you’ll need. Every transmission swap is a little different, and what types of bolts you’ll need, and how many you’ll need, are going to vary based on your individual build.
What this list can do is give you an idea of the parts that are commonly needed. Though everyone is prepared for needing a transmission, it’s important to think about everything you need before you get started.
A flywheel is the part of a manual transmission that connects to the engine.
- Clutch Disc
A clutch disc is the portion of a manual transmission that connects to the transmission.
- Pressure Plate
The pressure plate applies pressure to the clutch disc in order to engage and disengage the clutch.
- Pedal Assembly
The pedal assembly refers to the pedals inside the car that allow you to communicate with the clutch and the engine.
- Clutch Fork
The clutch fork is the part that applies pressure to the throwout bearing.
- Throw out Bearing / Slave Cylinder
The throw-out bearing presses against the center of the diaphragm spring, causing the pressure plate to push against the clutch disc.
- Clutch Alignment Tool
This is optional, but there’s a reason these parts come with clutch kits. Using this tool will ensure that the flywheel, clutch disc, and pressure plate line up correctly.
- Pilot Bushing
This piece supports the input shaft and clutch disc while allowing the flywheel to maintain an engine’s RPM even as the input shaft is slowing.
Kind of goes without saying, but these are the pieces that secure everything. You will need a lot of them, in a variety of shapes depending on your choices.
- Clutch Cable and Quadrant
You’ll need a way to communicate with the clutch, and a cable is important for that goal. The quadrant makes that cable adjustable.
This is the piece that holds the transmission to your car.
The driveshaft carries power from the transmission to your car’s differential. Lengths vary considerably, and driveshafts come in a variety of materials.
Preparing Car for New Transmission
The first step to any transmission swap is going to be removing the existing transmission. Because you’ll be installing a different transmission instead of simply a new one, this is actually a good time to go ahead and remove a whole lot more than that. Removing the center console, front seats, carpet, and knee bolster will ensure that you have an adequate workspace for the transmission swap, and you can go ahead and stow some of these parts (like the seats) away from your work site so that they don’t end up streaked in grease. You can also go ahead and remove the pedal assembly as well.
Once you have lowered the existing transmission out of your car, you can go ahead and start to perform the critical first steps.
Installing New Transmission
It’s incredibly important to refer to your manual throughout this process, and when in doubt, double-check. Even something small, like over or under torquing a bolt, can have negative consequences for your transmission swap.
You’ll be replacing the flexplate on your engine with a flywheel. It may be tempting to try to reuse the bolts from your flexplate for the flywheel, but usually, flywheel bolts will be shorter.
From there, you’ll connect the clutch plate, the pressure plate, and then the bellhousing. Don’t forget to use your clutch alignment tool throughout to make sure that everything is where it needs to be.
Once you’ve got those components in place, you can lift your new transmission into place and bolt it in using the crossmember.
Next, you’ll add the pedal assembly. This requires getting up under the dash, so if you have a small trustworthy child who has an interest in cars, it may be time to enlist their help with some quality “bonding” time.
This is obviously a very abbreviated version of the steps that are necessary, but hopefully, it gives you an overview of the size of the task you’re considering undertaking.
Transmission Swap Overview
Doing a total transmission swap of this nature is best done as part of a total overhaul, since you’ll be dealing with nearly every internal component of the car in order to make the swap work. Those who have used it as an opportunity to upgrade the mechanical attributes of their vehicle have been very satisfied with the results, while those who thought it would be a fun weekend lark are still lamenting their unfortunate life choices.
This is a great idea for those who have fallen in love with classic, rare, or otherwise hard to find cars, and who don’t mind bruising their knuckles. Despite some claims that it’s impossibly challenging, there are more than a few amateur hobbyists who have had great success simply by taking their time and having a good understanding of what they were getting involved with before jumping all the way in.
Image Credit: Jalopnik, Mustangs and Fords