Transmission Basics: Understanding the Basic Parts

By Mister Transmission

Before you hand over the keys, brush up on the basics of automatic transmissions so you can understand why your transmission is acting up. Here we’ll cover the basic parts of a transmission, basic transmission problems and how to know if a rebuild is in your future.

What is a Transmission?

The transmission allows you to shift your car from gear to gear, knowing how fast you need to go and how quickly you need to get there. Remarkable stuff.

Parts of a Transmission: 101

While there are many little parts inside, your transmission is essentially made up of 4 key parts of systems:

Bell Housing: This is the cone shaped metal case that you can see when you peek underneath your car. If you have a front-wheel-drive car it’s stuck on the side of the engine under the hood. If your car is rear-wheel-drive, the transmission will be mounted underneath the car behind the engine.

Gears: Even though you’re not shifting them, an automatic transmission has gears. They are broken into main gears and planetary gears. You need all of these to be able to drive.

Fluid: Transmission fluid is very important to an automatic transmission. All of the magic happens in the fluid. Most cars come with red transmission fluid, good to know if you are looking for a leak.

Filter: All of that fluid has to be clean for your car to shift gears at the right time. To keep things fresh, your transmission has a filter to catch any gunk.

Transmission Problems: 101

If your car won’t start or doesn’t run smoothly, these problems are caused by the same faults in your transmission, so whichever your car is doing, the following applies:

Is your fluid level correct?

It’s important to check your transmission fluid at least twice a year. Not only can a low fluid level cause your car to shift poorly, it can eventually lead to transmission damage, and a costly repair. If your car seems to be losing fluid on a regular basis, you may have a leak.

Is your transmission leaking?

Checking for leaks isn’t as difficult as it may seem. The transmission is a closed system, so there are only a few places that can spring a leak. Unless it’s been changed to a non-dyed fluid, your car will have red transmission fluid. Here are a few places to check for leaks:

  • At the filler tube base.
  • At the drain hole underneath the transmission.
  • Between the transmission and the engine.
  • At the selector shaft – the rod that connects your gear shift to the transmission.
  • At the speed sensor mounting point: This will either be your cable screwing into the transmission housing or an electronic sensor bolted to the housing.
  • In the radiator: If your car has a transmission cooler, it’s possible that a leak will cause transmission fluid to leak into the radiator fluid. They don’t mix well, so you’ll see it floating around in there.

Is Your Filter Clogged?

Your transmission’s filter is vital to its performance. If you haven’t replaced your filter in a while, or ever, be sure to do this before you start talking about rebuilds or replacements.

Time for a Rebuild?

When your transmission is worn out, you’ll have to have it rebuilt. For some makes and models of car this is true a little too often. The important thing is checking any other possible causes to your problem before you have it taken apart. If you haven’t replaced your filter yet, start there as this fixes a good percentage of transmission problems. If your filter is in good condition and nothing simple is out of adjustment, it’s likely you’ll need a rebuild. The good news is that at Mister Transmission we offer a rebuild warrantee so you’ll know it will get fixed and stay fixed.

Generally, transmission problems can’t be fixed by the average do-it-yourselfer. There are just too many specialized and expensive tools and pieces of equipment needed. We recommend keeping up with your regular maintenance to keep you out of the shop as much as possible.

Want to know more?
Visit one of our locations

image-reviews image-reviews
Customer Reviews
Honest. Fair prices. The only...
Scott Millson
Honest. Fair prices. The only place I’ve trusted for car repairs in the past 10 years
Date: July 7, 2025
Website: Google
On June 30th 2025 I...
Audie D
On June 30th 2025 I was having such a horrible day. My boyfriend changed my transmission oil a few days prior. When I would reverse my car everything would shut off. 10 minutes to get out of a driveway is insane. The 30th of June i called Mister Transmission and Rob picked up and said I could drop my car off and he’d look into it. Rob and the man working with him were truly amazing. From the moment I walked into the building I was greeted. He didn’t try to con me as I am a female. Rob has a pure heart of gold. When my car was there it didn’t do any of the shutting off and they did every diagnosis test. I was beyond anxious and having a bad day Rob really calmed down and lightened the mood. Thank you Rob
Date: July 7, 2025
Website: Google
I would first like to...
S Williams
I would first like to say the customer service and Mister Transmission is none like I have ever experienced. I had the pleasure of speaking with Denise who was so professional, patient and indescribably kind. Not only did she take the time to detail what my car needed and how long it would take, they took the time to provide alternate cost efficient options. For those looking for transmission repairs , I promise you you will find no better!!!
Date: July 7, 2025
Website: Google
Great reliable friendly service
Joe Macdonald
Great reliable friendly service
Date: July 7, 2025
Website: Google
Thses guys are pros after...
Nathan Chartrand
Thses guys are pros after dealing with another transmission shop not checking endplay in the crankshaft my engine is destroyed a standard practice any reputable shop should be doing
Date: July 6, 2025
Website: Google
Hi I had my 1966...
Craig
Hi I had my 1966 Chevelle Malibu SS in at Mister Transmission Sarnia to have the transmission worked on last year. Mike in the back shop worked on my car (pride and joy). He did the repairs that was needed done and a few extra things done without request. The car ran like a dream when I got it back. The cost was lower then they said it would be. I'm very fussy on who works on my car. The owner (manager) was awesome to deal with. Then this week 04 July 2025 I needed a shift cable repaired as I was headed out with my car . I went to the shop and they were over loaded with work. Mike made time to get my car fixed so I could use it on the weekend. They went the extra mile to get my car fixed and again I could not complain about the cost to repair the cable. I fully recommend them and the people that work there are outstanding. A special thanks to Mike who worked on my baby(my car) thanks so much guys. They are my go to shop with my Classic car and all my vehicles.
Date: July 5, 2025
Website: Google
I had a fantastic experience...
Xavier Montenegro
I had a fantastic experience with the whole Mr. Transmission team. Jordan and Jason are fantastic at their jobs, and they are truly willing to be honest and completely transparent with you. I took my 2018 Sierra to them for some transmission work (shocker), and they were quick, and the transmission now works fantastically. There were some small hiccups, the transmission initially acted a little weird, but they were quick to correct that. I had my spark plugs and a few coils swapped over here. One of the coils they got from GM blew up and took a couple of fuses with it. They comped the tow and had it fixed quickly, and were incredibly apologetic about the whole thing. Overall, if you are looking for quality service from a tried and true team, this is the place you want to go.
Date: July 5, 2025
Website: Google
Hi I had my 1966...
Craig
Hi I had my 1966 Chevelle Malibu SS in at Mister Transmission Sarnia to have the transmission worked on last year. Mike in the back shop worked on my car (pride and joy). He did the repairs that was needed done and a few extra things done without request. The car ran like a dream when I got it back. The cost was lower then they said it would be. I'm very fussy on who works on my car. The owner (manager) was awesome to deal with. Then this week 04 July 2025 I needed a shift cable repaired as I was headed out with my car . I went to the shop and they were over loaded with work. Mike made time to get my car fixed so I could use it on the weekend. They went the extra mile to get my car fixed and again I could not complain about the cost to repair the cable. I fully recommend them and the people that work there are outstanding. A special thanks to Mike who worked on my baby(my car) thanks so much guys. They are my go to shop with my Classic car and all my vehicles.
Date: July 5, 2025
Website: Google
These guys do good work....
Hunter Frederick
These guys do good work. And a fair price. 👍👍
Date: July 3, 2025
Website: Google
Mandy was extremely helpful in...
Don Brindle
Mandy was extremely helpful in getting out 2009 VW beetle back on the road, we are from out of town and he was very compassionate to our situation and helped at every level, if you are in Cambridge and need help, Mandy is your man!
Date: July 3, 2025
Website: Google
Featured Services
Transmission Repair

The evolution of transmissions has made these machines and systems increasingly complex. When transmission repairs are required, determining the cause and cure for what ails can be tricky.

Read More
Transmission Technology

At Mister Transmission we have access to leading-edge diagnostic equipment, enabling us to offer you the fastest and most accurate findings about what’s going on inside your vehicle’s transmission.

Read More
Transmission Maintenance & Service

Just as you have other parts of your car serviced, your transmission needs maintenance to ensure a long life and avoid transmission problems.

Read More
Mister Transmission Blogs
Recent Blogs
Ford Transmission Problems Explained: Sy...
Ford has produced many popular vehicles known for power and innovation. However,
Read More
June 30, 2025
Finding A Reliable Transmission Shop Nea...
The transmission is the heart of your vehicle’s power system. When it starts to
Read More
June 23, 2025
Complete Guide To Transmission Replaceme...
Transmission replacement becomes necessary when wear and damage go beyond repair.
Read More
June 16, 2025
Is Your Vehicle Showing Transmission Pro...
Transmission problems often begin with small signs that many drivers choose to
Read More
June 9, 2025
What Does A Transmission Flush Do? Is It...
A transmission flush is a professional service designed to remove old, degraded
Read More
May 31, 2025
Why Is My Car Not Shifting Gears Properl...
Have you noticed your car struggling to shift gears? Whether it hesitates, jerks, or
Read More
May 23, 2025
What Happens When Transmission Fluid Is ...
Transmission fluid plays a critical role in keeping a vehicle’s transmission system
Read More
May 15, 2025
Used Transmission Vs. Rebuilt Transmissi...
Choosing between a used transmission and a rebuilt transmission is an important
Read More
May 7, 2025
Preventative Transmission Maintenance: 5...
A vehicle's transmission is one of its most critical components, responsible for
Read More
April 30, 2025
Transmission Rebuild Vs. Replacement: Wh...
When a vehicle's transmission begins to fail, owners often face a crucial decision:
Read More
April 23, 2025