Transmission Leak: Quick Fix Guide

If you have a 350 transmission leaking around the trans pan, there are several potential causes. Transmission fluid leaks are often caused by a faulty gasket or a punctured transmission pan. The gasket provides a seal between the pan and the transmission, and it can wear out over time, leading to fluid leaks. Other possible causes include loose bolts, holes in the pan, a bent transmission pan, or a leaking transmission drain plug. It's important to identify the exact cause of the leak to fix it appropriately. Transmission leaks should be repaired as soon as possible to avoid extensive damage and costly repairs.

How to identify a transmission pan leak

A transmission pan leak can cause a host of issues for your vehicle. With a leak, the transmission system doesn't get the lubrication and pressure it needs, which can cause a host of problems. Here are some ways to identify a transmission pan leak:

Reddish-Brown Spots Under the Vehicle

Keep an eye out for reddish-brown stains on your garage floor or driveway. This is often the first sign that there is an issue with the level of your transmission fluid. These spots can be in the centre of the vehicle (RWD) or on the side of the vehicle where the transmission is located (FWD). Manual gearboxes may leave light brown or reddish-brown stains on the ground.

Gear Shifting Issues

If there isn't enough transmission fluid to keep everything lubricated, you may notice a delayed response when the gears shift or a failure to shift at all. The transmission may go into a "limp home mode", where it remains in one gear to allow you to get to your technician. A manual gearbox may become noisy or difficult to shift when the fluid is low.

Check the Fluid Level

If your automatic transmission is equipped with a dipstick, check the fluid level. If it is low, this is another sign of a leak. Many newer vehicles do not have a dipstick or require the vehicle to be raised to check the fluid level. Manual gearboxes also require the vehicle to be raised to check the fluid level.

Puddle of Transmission Fluid

If you see a puddle of green or red-coloured oil under where your car was parked, you may have a leaking transmission. This issue is considered normal but can take a toll on your car in the long run.

Transmission Slippage and Performance Problems

A low transmission fluid level can cause transmission slippage and other performance problems. Your transmission needs hydraulic pressure to connect the power between the car's engine and its wheels. If the pressure gets too low, transmission fluid will start leaking from the engine.

Overheating Transmission

One of the vital roles of your vehicle's transmission fluid is to help keep the rotating components of the transmission cool. If the fluid levels get too low, it will be unable to cool the transmission properly, and your transmission will overheat and start to leak fluid.

Late Engagement

Stalled engagement between gears can result in low transmission fluid. When your car's gears are in 'neutral' or 'drive' modes, they need to build up a certain amount of pressure before the car can move. If the transmission fluid level is extremely low, it will dramatically delay the movement in your car and result in a leakage.

How to Diagnose a Transmission Pan Leak

If you can identify and locate the car's transmission from the underbelly of the vehicle, a leak can be relatively simple to spot. However, finding the root cause of the leaking transmission pan is a different story. To correctly find the source of the leak, you need to thoroughly clean off all fluids from the entire underbelly of your car and then add dye to your transmission system. After ensuring your car is filled with the proper levels of transmission fluid, take it for a 30- to 40-mile spin. With slow leaks, you may need to drive your vehicle over 100 miles to notice fluid coming out.

Common causes of transmission fluid leaks

Transmission fluid leaks are a serious issue that can cause significant damage to your vehicle if left unattended. The fluid is usually red, but it can also be pink or brown. It has a consistency that is thicker than brake fluid but not as thick as engine oil. If you notice a leak, it is important to get it checked right away. Here are some common causes of transmission fluid leaks:

Transmission Pan or Drain Plug

The transmission pan is located underneath your car and is susceptible to damage from road debris such as loose rocks. If the pan gets punctured or there are loose drain plugs or bolts, a leak can occur. A small puncture may take longer to notice, but a large hole will result in rapid fluid loss. In some cases, the drain plug may be over-tightened or stripped, causing fluid to leak out.

Broken Seals

An automatic transmission maintains hydraulic pressure through a series of transmission seals. Over time, these seals can crack and wear out due to heat exposure or an excess of transmission fluid in the system. Leaks commonly occur at the input or output shaft, but they can also happen at the transmission pan, driveshaft, plug seals, sensors, shifter housing seal, valve body, tail housing seal, or speedometer input seal.

Transmission Pan Gasket Failure

The transmission pan gasket is exposed to high temperatures, which can cause it to crack and leak. This can also be due to manufacturing defects, improper installation, or long-term wear. A failing gasket should be replaced as soon as possible to prevent further issues.

Torque Converter Leakage

The torque converter propels transmission fluid throughout the system. If the torque pump develops a crack or the needle bearings become damaged, it will result in a transmission fluid leak.

Cracked Fluid Lines

Transmission fluid lines are made of steel or aluminum and are located underneath the vehicle. They can be damaged by road debris or heat exposure, leading to cracks or breaks in the lines.

Steps to fix a leaking transmission pan

A leaking transmission pan can cause a lot of problems for your car if not addressed promptly. Here are the steps to fix a leaking transmission pan:

Step 1: Identify the Fluid

Transmission fluid is typically translucent reddish in colour, but it can darken to brown or black as it ages. It also has a mildly sweet smell, which is distinct from the pungent odour of motor oil. Check the motor oil and ATF levels to identify the leaking fluid. If you're still unsure, place a clean piece of cardboard under the vehicle to catch the drips and help with identification.

Step 2: Locate the Source

Cleaning the entire undercarriage of your vehicle with a degreaser or brake cleaner can help locate the source of the leak. Once the undercarriage is clean, drive the car for a short distance and then park it on a piece of cardboard. Use a bright flashlight to inspect the transmission and its components for any signs of leakage. If you're still unable to locate the source, consider using an automotive leak detection kit, which typically includes a fluorescent dye, a UV light, and tinted glasses.

Step 3: Assess Your Options

Transmission problems often require the expertise of a professional mechanic. However, if you possess the necessary skills and feel confident in your abilities, you may consider repairing the leaking transmission pan yourself. Keep in mind that transmission repairs can be complex, so it's essential to carefully consider your options before proceeding.

Step 4: Gather the Necessary Tools and Materials

If you decide to repair the leak yourself, you'll need to gather the appropriate tools and supplies. This may include a vehicle-specific shop manual, which can provide step-by-step instructions and parts/tool lists. Online platforms like YouTube can also be a valuable resource, as you may find videos of mechanics who have tackled similar issues. Some common tools and materials you may need include:

• Jack, jack stands, or ramps
• Metric/standard socket and wrench sets
• Pliers/needle-nose pliers
• Tarp/cardboard to prevent messes
• Cat litter for cleanup
• Correct type of ATF (refer to your owner's manual)

Step 5: Drain the Fluid

Place a catch pan underneath the transmission pan and drain the ATF. Some vehicles have a drain plug, making this process easier. If your vehicle doesn't have a drain plug, carefully unbolt the transmission pan. As you do this, the fluid will start to drain, so be prepared to catch the flow and avoid getting it on yourself.

Step 6: Fix the Problem

This step will depend on the specific cause of the leak. If the leak is due to damaged fluid lines, replace the entire line. If the transmission pan gasket is the issue, clean off the remnants of the old gasket and install a new one. If the transmission pan itself is damaged, you'll need to replace it with a new or used pan, ensuring you also install a new pan gasket.

Step 7: Refill and Test

Once you've made the necessary repairs, lower the vehicle and refill it with the correct type and amount of transmission fluid. Check for leaks, shift through all the gears, and take the vehicle for a test drive to ensure the problem has been resolved. Don't forget to clean up any messes made during the repair process.

When to seek professional help

It is recommended to seek professional help when dealing with a transmission fluid leak. This is because transmission fluid leaks can lead to severe problems and costly repairs if not addressed promptly and properly. While there are DIY approaches to fixing transmission leaks, consulting a professional mechanic is the best course of action to ensure the issue is resolved correctly and safely.

• Low transmission fluid level: If you check the fluid level using the dipstick and find that it is low, this could be a sign of a leak.
• Burned-smelling transmission fluid: If the transmission fluid has a burnt smell or appears brown, it could indicate that the fluid is burning due to a leak.
• Difficulty shifting gears: If you experience difficulty shifting gears or the vehicle slips gears, it could be a sign of low transmission fluid due to a leak.
• Gear shifting delays: Delayed response when shifting gears or failure to shift at all could be due to insufficient transmission fluid caused by a leak.
• Noisy manual gearbox: In the case of a manual gearbox, a transmission fluid leak may result in noisy or challenging gear shifting.
• Puddles of fluid: If you notice puddles of reddish-brown or semi-transparent/honey-colored fluid underneath your vehicle, it is a clear sign of a transmission fluid leak.
• Burning odor: A burning odor coming from your car may indicate that the transmission fluid is leaking and burning.

In any of these cases, it is advisable to consult a professional mechanic as soon as possible. They have the necessary tools, expertise, and experience to accurately diagnose the source of the leak and perform the required repairs. Attempting to fix the leak without professional knowledge can be dangerous and potentially lead to more severe issues.

Preventing transmission pan leaks

A transmission pan leak can cause severe damage to your vehicle, so it's important to know how to prevent it. Transmission pans are typically located in the undercarriage and act as a reservoir for transmission fluid. Due to their location, they are prone to damage from speed bumps, road debris, and uneven road surfaces.

To prevent a transmission pan leak, it is crucial to avoid impact damage caused by debris and uneven road surfaces. Driving with insufficient ground clearance can also damage the transmission pan and other nearby components. Normal vehicle operating conditions, such as heat and vibration, as well as the vehicle's age, can cause the transmission pan, gasket, and bolts to warp and wear out over time, leading to leaks. Therefore, it is important to regularly inspect and maintain these components.

When installing or reinstalling the transmission pan, care must be taken not to over-tighten the bolts, as this can deform the pan and damage the gasket, leading to leaks. It is recommended to progressively tighten the bolts until the tabs just come into contact with the transmission housing. Wait for the rubber to compress, then complete the tightening sequence.

Additionally, regular maintenance, such as changing the transmission fluid and filter every 60,000 miles, can help prevent leaks and keep your transmission in good condition.

Frequently asked questions