Should I do a Manual Transmission Fluid Change? | AG Auto

Checking your transmission fluid is easily forgotten about as it’s not common practice to change it on a routine basis. Nonetheless, it is one of the most important fluids in your vehicle and if it isn’t changed per your vehicle manufacturer recommendations, it can lead to compounding problems that will end up damaging your transmission. 


Transmission problems become more prominent over time due to constant wear on its components- even when properly cared for. In most cases, especially with older vehicles, replacing the transmission is not a worthwhile investment because a new transmission can be pricey. When the cost to repair the car exceeds the value of the car, it is common for its owners to deem their car totaled and look into purchasing another vehicle. 


If you have any questions or concerns about the condition of your transmission, call our expert mechanics at AG Automotive. We will be happy to answer any questions you may have and get you on our schedule so you can get back out on the road and drive with confidence.


If you drive an automatic transmission, check out our blog about our automatic transmission fluid service!


Automatic vs manual transmission fluid:


Although both automatic and manual transmissions require transmission fluid to function, transmission fluid in automatic and manual vehicles serve a different function and their maintenance needs are dramatically different from one another. 


In manual transmissions, the transmission fluid performs three important functions:


  • Promote smooth shifting


Nothing feels better than the crisp, clean feeling that comes with nailing the perfect shift. Manual transmissions use synchronizers that equalize the speed of the gear being engaged, allowing for smooth and crisp shifts. Proper lubrication of these moving parts is a huge factor in the “perfect shift” feeling. Transmission fluid that is too thick can cause additional friction between all the moving parts, producing high temperatures that can deteriorate the transmission fluid. On the other hand, transmission fluid that is too thin can cause the synchronizer to engage too quickly, resulting in hard shifts, gears grinding, and additional transmission wear. 


  • Lubrication to protect against wear


Transmission fluid should also effectively provide sufficient lubrication to all of the intertwining gears and metal parts. Fluids that have the proper lubrication qualities help prevent damage to the metal components caused by friction. Fluids used in manual transmissions are less viscous than the fluid used in automatic transmissions to ensure the moving components have a thick and durable coating. 


  • Protect brass synchronizers


The fluid used in manual transmissions has to provide the ideal lubricating properties described above, as well as be compatible and safe for use among different types of metal. The syncro is made of brass, which isn’t the most durable metal. So finding a fluid that will protect and provide the proper lubrication properties for the syncro


In automatic transmissions, the transmission fluid performs four important functions:


  • Act as hydraulic fluid


Unlike manual transmissions, automatic transmissions use a hydraulic system. It changes through gears by distributing fluid throughout the system using internal pressure. When the ECU detects that it is time to shift gears, it sends a signal to the proper transmission solenoid to direct fluid throughout the valve body which then engages the correct gear. Automatic transmission fluid has a low viscosity because if the fluid is too thick, it will have trouble flowing through the valves which will lead to sluggish feeling shifts. Old automatic transmission fluid also contains foam inhibitors which prevent the fluid from bubbling up during use. The bubbles may pop in the valves and inhibit the hydraulic system from functioning properly. 


  • Provide anti-frictional properties


Like with many things in life, the fluid can’t be too thick, nor too thin- it has to be just right in order to function properly. Engagement and disengagement of metal plates within the clutch pack must occur smoothly. Transmission fluid that is too thick may cause a delay in how the moving plates interact with each other, diminishing the feeling of a confident and crisp shift.


  • Lubrication to protect against wear


The viscosity of transmission fluid in an automatic needs to be able to flow just enough to squeeze through the tight valves to create the pressure needed to shift gears. But it also has to be thick enough to leave a protective coating that helps prevent damage to the intertwining gears and metal parts caused by friction.


  • Reduce heat caused by friction


Just like engine oil, transmission fluid can deteriorate over time due to age or when other contaminants get mixed in. Oxidation can chemically break down transmission fluid which causes the fluid to become sludge-like and clog the narrow valve bodies. Automatic transmissions are known to run hotter than manual transmissions, so cooling additives have to be mixed in with the fluid to prevent chemical breakdown. Some newer automatic transmissions have fluid coolers to counteract the heat in case the additives can’t do the job alone. 


When should you have a manual transmission fluid service?


Although there is no consensus on how many miles you can go before getting a transmission fluid service for an automatic transmission, we recommend that you follow your vehicle manufacturer’s recommendation that can be found in your vehicle’s owner’s manual. 


The service interval really depends on the make, model, mileage and what the vehicle is used for on a daily basis. Some manual transmissions in heavy-duty vehicles will require a transmission fluid service every 30,000 miles, while some regular commuter vehicles can last up to 80,000 miles. Most manufacturers will recommend changing the transmission fluid in your manual vehicle every 30,000 to 60,000 miles.


If you have any questions or concerns about the condition of your transmission, call our expert mechanics at AG Automotive. We will be happy to address all of your questions and concerns or get you scheduled for a service so you can get back out on the road in no time!


Common warning signs that indicate your manual transmission needs a fluid change service:


  • Difficulty shifting through gears 
  • Transmission is slipping out of gear
  • Transmission won’t engage
  • Hear clunking, squealing, or humming noises when shifting gears
  • Vehicle is shaking while accelerating
  • Smell something burning
  • Check engine light is illuminated


Schedule your transmission fluid service for your manual vehicle today!


If your vehicle is experiencing stiff shifting and noise from the gearbox, have difficulty shifting, or see puddles underneath your vehicle, schedule an appointment with AG Automotive and will get you back on the road in no time after we identify that it needs a transmission fluid service. Our expert technicians have the tools and knowledge to test, clean and replace worn engine components quickly and efficiently.


We want the job to be done right the first time so we ensure your transmission system is working properly and exceeds the manufacturer’s specifications. We offer our customers a full-service manual transmission fluid service:


-Remove fill plug and check fluid level

-Drain all transmission fluid 

-Clean drain plug magnet

-Replace manual transmission filter (If applicable)

-Clean and check transmission breather tube including for proper routing

-Add new fluid 

-Add transmission treatment (If applicable)

-Clean and test drive

-Check for proper shifting and drivability 

-Recheck fluid level and for leaks

-Quality check 

Don’t Second-Guess the Condition of Your Vehicle

Many auto owners struggle to know if the right work was done the right way on their car. As a courtesy, we provide digital vehicle inspections and photos so you can quickly and easily see what our experienced, professional technicians are seeing. Overall, we go the extra mile to help you make informed decisions on the repair and maintenance plan of your vehicle, so you can drive with confidence every time you get behind the wheel.