As a car owner, you’ll agree that there’s almost nothing more troubling and frustrating than automatic transmission grinding noise when shifting gears.
The transmission may make several noises when shifting gears. These noises include rattling, whining, grinding, and clunking noise when shifting gears or accelerating.
Most times, any transmission noises indicate a severe underlying transmission problem. A mechanic should track where these noises are coming from and proffer solutions before they escalate to total transmission failure.
This article will discuss the causes of automatic transmission noise when put in gear. We’ll also look at how to rectify them.
What Causes Automatic Transmission Grinding Noise When Put In Gear?
The most common reason a transmission makes a grinding noise when you put it in gear is low transmission fluid or degraded/contaminated transmission fluid.
However, there are undoubtedly other mechanical faults that could be causing the grinding sound, such as a worn-out shift linkage or a worn-out torque converter.
#1. Low Transmission Fluid.
Low transmission fluid makes it hard for the valve body to smoothly engage the clutch packs and bands while also robbing the gears of the lubrication they need, causing a grinding or whining noise as the first gear engages.
This is usually accompanied by hard shifts into second gear where the engine revs high for a long time before the gear finally catches.
If the transmission fluid is severely low, it might grind going into first gear, travel a few hundred feet, and then suddenly slip out of gear when the valve body can’t maintain sufficient pressure.
Low fluid can eventually cause the transmission to overheat, which is more likely in stop-and-go commuter traffic.
#2. Degraded or Contaminated Transmission Fluid.
Transmission fluid that’s lost its lubricating properties as it degrades or has become contaminated with debris can also cause an automatic transmission’s gear to grind when shifting gears.
This first starts to show up when putting the car in first gear (Drive) or reverse when the load on the gear is the heaviest. However, you’ll gradually notice the grinding noises when it shifts into second and third gear.
When you check your transmission fluid, and it looks dark or smells like burned rubber, it’s a sure sign that it’s started to degrade.
Though the even bigger concern here is if you see debris or fine particles suspended in it, which is a sign that a leak or something is allowing outside material into the system.
Fine metal flakes suspended in the fluid are also a serious worry. This is a sign that the grinding of the gears is causing untold internal damage, and the car needs to be parked to prevent more serious problems.
If the fluid is dark but has no signs of contamination, it might just be that it’s gotten old, or you might have unknowingly overheated the transmission recently.
If you’ve been doing a lot of towing or stop-and-go driving, the excess strain and heat on the transmission could have caused the fluid to break down.
#3. A Clogged Transmission Filter.
A transmission filter that clogs over time or particulate matter can make it hard for the gears to get the proper lubrication they need, causing them to grind in the low-end gears like first and reverse.
You might even find the car grinding into first gear and traveling ways before mysteriously slipping back into neutral even though you have the gear selector in Drive.
In a scenario like this, you might check the transmission fluid only to find it looks full on the dipstick. Yet it acts just like the transmission fluid is low because sufficient fluid can’t make it from the oil pan through the filter to the valve body and the gears.
#4. Bad Transmission or Engine Mounts.
If the support structure provided by a transmission or engine mount fails, the deviation in the relationship between the input shaft and the output shaft can cause a grinding noise when the transmission goes into gear.
This will be more pronounced in the lower gears at first, but as the mount degrades, you’ll likely hear grinding noises and clunking sounds throughout all the gears.
A bad transmission mount will also transmit vibration to the steering wheel or the gear selector. You might have the engine running in the park or neutral, and everything feels normal.
Then, when you put it in Drive or Reverse, the steering wheel starts shaking with the force of the transmission engagement.
They’re just robust pieces of heavy-duty rubber with metal fastener hardware.
#5. A Torque Converter Problem.
Any time there’s a problem with the torque converter, there will be a problem transferring power from the engine to the rest of the transmission, which can cause delayed gear changes with grinding noises.
In a scenario like this, the transmission will often hesitate to shift gears, or it might make an overly loud clunk after grinding as it slips into gear when the engine is revving too high.
If the disparity between the torque converter and the engine’s RPMs is too high, the car might finally grind into gear and then suddenly stall. You’ll probably also notice that the car feels down on power, even though the engine seems to be running properly.
Many torque converter problems will also cause transmission fluid leaks at the seal where the bell housing joins to the transmission housing.
Sometimes, a bad torque converter will trigger a transmission or check engine warning light. When it does, it will throw a code you can read.
- Code P0740 is a blanket code for Torque Converter Clutch Circuit Malfunction.
- Code P0741 is for the Torque Converter Clutch Circuit Performance stuck-off.
#6. A Dirty or Clogged Valve Body.
If dirt or contaminants have made it into the transmission’s valve body, it won’t be able to rapidly divert fluid pressure, causing delayed activation in the clutch pack leading to grinding noises as first gear or reverse finally engages.
Problems with a transmission’s valve body tend to show up early in the low gears where the most pressure and force transfer is called for. In time, you’ll start to notice hesitation in all the gear changes.
In short order, you’ll probably also notice things like the RPMs jumping up when the transmission shifts up. Gears can start slipping and/or clunking as they engage. The grinding noise persists as clutch packs and bands fail to keep up with the lag in demand.
Since the valve body works with the TCM to act as the “Brain” of the transmission, you’ll eventually get a check engine or transmission warning light. When you do, it might throw one of the following codes.
- Code P0700 is a blanket code for a transmission problem and will occur in conjunction with pretty much any valve body problem.
- Code P0783 means the PCM has detected an irregular signal from the transmission’s input/turbine speed sensor.
- Codes P2707, P0829, &P0751 are codes for a problem with the various shift solenoids. If you get more than one of these codes, it could be an issue with the valve body affecting the performance of the entire shift solenoid pack.
#7. A Worn-Out Transmission Pump.
If the transmission pump is worn out or dying, it won’t be able to effectively circulate the lubricating transmission fluid, leading to grinding noises from excess friction between the moving parts.
Since first gear and reverse bear the most force, you tend to hear the grinding noise the loudest when you first put it into gear.
As the transmission pump continues to die, you’ll also start hearing whirring and whining noises.
The grinding sound will also be prevalent at every gear change until it’s constant whenever the car moves. You’ll probably also notice a massive lag in acceleration, and the transmission will start to overheat in stop-and-go driving.
#8. Worn-Down Gear Teeth.
Worn-down teeth on the sun, ring, or planetary gears can easily cause a grinding noise, which is most prominent in first gear and/or reverse. This is when the gears are first engaging, and the stresses on the gear teeth are the highest, causing them to grind and slip.
In a scenario like this, you’ll usually see a lot of metal flakes suspended in the transmission fluid from tiny bits of the gears wearing off.
Overall transmission performance will also be sloppy, with the car feeling like it’s down on power. Depending on how severe the wear and tear is, the transmission might slip when accelerating.
Diagnosis and next steps
Mechanics typically approach this issue by confirming fluid health, scanning for transmission codes, and listening to the noise with the vehicle in gear. The steps below outline a typical diagnostic path:
- Check transmission fluid level and condition (color, smell). Top up if advised by the vehicle manufacturer and replace if burned or very dark.
- Inspect for fluid leaks under the vehicle and look for signs of trouble, such as a burnt smell or dark, sludgy fluid.
- Scan for transmission-related diagnostic trouble codes (DTCs) with an OBD-II scanner to identify valve body, solenoid, or sensor problems.
- Test-drive with attention to where the noise occurs (cold vs. hot, in gear vs. when accelerating, at idle). Note RPMs and vehicle speed.
- Inspect driveline components (driveshaft U-joints, CV joints, axles) for wear or binding if noise persists after fluid service.
- Have a professional perform a more thorough diagnosis, which may include pan inspection, pressure tests, or internal transmission inspection if codes indicate a problem.
How To Fix Automatic Transmission Grinding Noise?
If you hear grinding noise when you put your automatic transmission in gear, one or more of the problems listed above may have caused it. So, how do you solve these problems?
Let’s take a look at a few steps to follow to address each of the possible causes of automatic transmission grinding noise.
#1. Top Up or Replace the Transmission Fluid.
If the transmission fluid is low, topping it up can often fix the grinding noise. But if the fluid is dirty or contains burnt particles, you should replace it with a new batch of fluid.
To top up or replace the transmission fluid, you’ll need to:
- Open the engine cover.
- Locate the transmission fluid dipstick.
- Remove the dipstick and wipe it clean.
- Reinsert the dipstick and check the level of fluid.
- Add more fluid, if necessary, until the level reaches the “full” mark.
- If the fluid is contaminated, drain it and refill the transmission with fresh fluid.
- Close the engine cover.
#2. Clean the Transmission Filter.
If the transmission filter is clogged, cleaning it can help to eliminate the grinding noise. To clean the filter, you’ll need to:
- Open the engine cover.
- Locate the transmission filter. You’ll find it right above the transmission pan.
- Remove the filter and clean it using a degreaser or solvent.
- Rinse the filter with clean water.
- Secure the filter back in place.
- Close the engine cover.
#3. Replace the Synchronizers.
If you think the synchronizers are at fault, you can replace them by following these steps:
- Remove the transmission pan.
- Disassemble the transmission.
- Locate the synchronizers.
- Remove the synchronizers using a pair of pliers or a wrench.
- Install the new synchronizers.
- Reassemble the transmission.
- Refill the transmission with fresh fluid.
#4. Replace the Gears.
If the gears are bent or damaged, replacing them is your best bet for eliminating the grinding noise. To replace the transmission gears, you’ll need to:
- Remove the transmission cover.
- Disassemble the transmission.
- Remove the gears.
- Replace the gears.
- Reinstall the transmission cover.
Note: Ensure you have the proper tools and knowledge before replacing the gears yourself.
#5. Replace the Torque Converter.
If a damaged torque converter is the cause of the grinding noise, replacing it should solve the problem. To replace the torque converter, you’ll need to:
- Open the engine cover.
- Remove the transmission pan.
- Disassemble the transmission.
- Remove the torque converter.
- Install the new torque converter.
#6. Replace the Transmission Pump.
If the transmission pump is worn-out, replacing it can help fix the grinding noise. To replace the transmission pump, you’ll need to:
- Open the engine cover.
- Locate the transmission pump.
- Remove the pump and replace it with a new one.
- Reinstall the pump.
- Close the engine cover.
#7. Clean or Replace the Valve Body.
If the valve body is dirty or damaged, cleaning or replacing it can help to eliminate the grinding noise. To clean or replace the valve body, you’ll need to:
- Open the engine cover.
- Locate the valve body.
- Remove the valve body and clean it using a degreaser or solvent.
- Rinse the valve body with clean water.
- Reinstall the valve body. Replace the current valve body if you spot signs of damage.
- Close the engine cover.
#8. Replace the Transmission Mounts.
If the transmission mounts are worn-out, replacing them can help fix the grinding noise. To replace the transmission mounts, you’ll need to:
- Jack up the car and remove the wheel on the side of the transmission.
- Remove the bolts that hold the transmission mount to the car’s frame.
- Install a new transmission mount and reinstall the bolts.
- Lower the car.
FAQs.
Q: What does it mean when your transmission is grinding?
Transmission grinding noise is an indication of underlying tranny issues. The clutch systems are not properly disengaging or engaging from the engine. It can happen for many reasons, which we’ve outlined above. In manual tranny, it could be bad driving habits.
Q: Can low transmission fluid cause grind?
Transmission fluid differs from engine oil, which requires constant changes. However, they perform the same cooling and lubricating purposes.
The tranny unit is a complex and integral component of a vehicle. It transmits engine power to the wheels for the vehicle to move. The tranny fluid should be at the recommended level throughout its lifespan.
A good functioning transmission will shift between gears smoothly and offer a seamless driving experience. Low transmission fluid will cause the gears to miss, which will cause a grinding noise.
Q: Why does my transmission grind when I put it in reverse?
Misaligned gears cause a typical grinding noise when shifting to reverse. If it happens occasionally, it means the transmission has not fully disengaged from the engine, and the gears are still spinning. A quick trick to avoid it is to shift to drive before shifting to reverse.
Poor tranny lubrication, worn gears, or other internal issues can also cause it. The moment you notice grinding gears in reverse, check your tranny fluid and ensure it’s on the right level.
Q: What do grinding gears feel like?
A grinding gear is an unpleasant and troubling sound, for sure. It feels awful and embarrassing when you hear a grinding noise from the gears. It affects the overall transmission performance and poses more danger to the gears.
Q: What happens when you grind gears?
Grinding gears happens when a driver tries to change gears without the clutch or without fully engaging the clutch.
When you grind your gears, it does not affect the clutch as far as you don’t slip the clutch. It’ll only have normal wear. However, you’re damaging or ruining the Synchro-mesh.
Final Words
At this juncture, we’ve explained the causes and solutions to automatic transmission grinding noise when put in gears. Whenever you hear a grinding noise from the transmission or feel the gears are slipping, check the fluid level.
If you have adequate transmission fluid, consider driving down to a mechanic garage as soon as possible. It may be time for a routine transmission service, or you have a faulty tranny component that needs replacement.