Depending on the make and model, an automatic transmission contains at least 1000 individual parts. Each one has to work in complete harmony with the next part, otherwise the whole mechanism will not function properly. Even the smallest miss-adjustment can have catastrophic consequences to the operation of the vehicle. Needless to say, you need to know what you’re doing in order to perform a successful transmission rebuild. So doing it in your home garage might take a bit of thoughtful consideration.
What Transmission Do I Have?
Removing the transmission
If you’re going to do a DIY transmission rebuild, you’re gonna have to take the transmission out of the vehicle. On a rear-wheel drive vehicle, this is pretty simple. But certain front-wheel drive vehicles will require you to partially remove the engine in order to access the transmission below it. You also have to be very careful not to damage any wiring, brake lines, or any other components that are located near the transmission. An automatic gearbox is very heavy, so be sure to drain the transmission fluid before you attempt to remove it from the vehicle.
What are we looking at?
With the transmission removed, you’re going to want to open up the transmission and figure out what you are working with. To do this, simply refer to the instructions in the shop manual that you hopefully purchased before attempting to rebuild a transmission on your own. You’re also going to need a full complement of tools, as well as an understanding of how to use them. One slight miss-adjustment can lead to a nonfunctioning transmission and a lot of wasted time. And while you’re grabbing things from the store, don’t forget to grab a master transmission rebuild kit. This contains all of the seals, gaskets, bearings, clutch discs and other ‘soft parts’ that you’ll need to rebuild the transmission.
Now, whether you follow a shop manual or YouTube video instructions, you have to be very cognizant of the order in which you remove the parts from the transmission case. There will be a lot of parts, sort of like a big mechanical jigsaw puzzle. If you’ve had previous mechanical experience, then it might not be as overwhelming to you. But if you’ve never done it before, you’re going to want to take your time and label things so you don’t get mixed up when you go to reassemble the transmission.
Clean & inspect
You’re going to want to clean all of the hard parts (gear sets, case etc.) with a good quality parts cleaner to remove all of the gunky buildup. This will make it easier for you to inspect all of the parts for damage. Every surface, gear tooth and curve needs to be checked for signs of cracking, warping and damage. At this point, transmission remanufacturing companies like Street Smart Transmission would also use specialized equipment to check the tensile strength and thickness of the metal, then check their findings against the original factory specifications for that transmission. If anything fell below the OE specs, it would be immediately replaced.
Putting everything back together
Following the step-by-step instructions in your manual, carefully replace all of the soft parts then reinstall all of the components in the specified order. Hopefully your master transmission rebuild kit had a few updated parts to address some of the factory design flaws that are common with your particular transmission. If not, you may want to spend some time on the good ole’ internet and figure out which updated components you should be using. Rebuilding a transmission is a very complicated job, and you want to use the right parts the first time so you don’t have to go back and redo your transmission rebuild sooner than you have to.
Once the transmission is reassembled, and you are confident that you don’t have any parts (or bolts) left over, then reinstall your rebuilt transmission in the vehicle and fill it with fresh transmission fluid. Assuming that everything goes well on the test drive, you should be a good to go. If the transmission does not seem to be performing properly, then follow the troubleshooting and adjustment procedures in the shop manual/transmission rebuild kit.
So, can I rebuild a transmission on my own?
Rebuilding a transmission is a very complicated job that you really shouldn’t attempt unless you have prior mechanical experience. But even if you do know a thing or two about cars, a transmission rebuild can still be an overwhelming task.
Why a remanufactured transmission might be a good option
While you can’t buy a brand-new transmission, a remanufactured transmission is a terrific alternative. These are completely reengineered and put together on a factory assembly line. They often contain a lots of upgrades over their stock form, which means many of the design flaws that result in premature failure of components can be eliminated. This can give a reman transmission a much longer service life than it originally had.
Remanufactured transmission companies like Street Smart Transmission put each of their reman transmissions through a rigorous build process that ensures a quality product every time. It starts with nearly 100 trained technicians that specialize in different aspects of the build process.
This remanufacturing process starts with the inspection team that test all of the critical components from the donor transmission to ensure that they meet the original equipment (OE) tolerances and specifications. The case, pumps, gears, shafts, valve body and torque converter are checked for hairline cracks, metal tensile strength, warping and other parameters. If any component fails to meet the required specifications, it’s discarded and replaced.
All the parts are then cleaned and sent to the appropriate stations on the assembly line for reassembly. Throughout the process, quality control managers inspect the build to ensure that it meets the desired specification. Any necessary modifications or upgrades that are needed to correct factory design flaws are also performed or added. The valve body is rebuilt and tested on a special dyno machine to ensure that it performs according to the specifications. All of the solenoids are also tested prior to installation.
Once the build is complete and passes its final quality control inspection, the newly remanufactured transmission is sent to the dyno room, where it’s tested on a special dyno machine using a proprietary software program called C.A.R.S. (Computer Aided Real-world Simulation). This cycles the transmission through a number of real-world driving situations, to ensure that it performs according to the factory specs. It also helps to break in all of the friction components, that way it’s completely tuned and ready to go once it’s installed.
Warranty – One of the benefits of buying a remanufactured transmission vs. a rebuilt transmission is the warranty. Street Smart Transmission for example, covers all of their reman transmissions with a 3 Year/Unlimited Mileage Nationwide Warranty (there is a mileage restriction for commercial vehicles). This covers parts and labor for transmission repairs performed by any licensed repair shop in the country. It’s also completely transferable if you ever decide to sell the vehicle. Compared to a mechanics warranty on a transmission rebuild, a remanufactured transmission warranty offers superior financial protection.
What Transmission Do I Have?
