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Gearbox Oil Cooler
- Porsche 911 1984-1986 3.2L
- Porsche 964 (911) C2 1989-93
- Porsche 964 (911) C4 1989-93
- Porsche 964 (911) RS 3.6L 1991-93
- Porsche 964 (911) RS 3.8L 1991-93
- Porsche 964 (911) TURBO 3.3L 1991-93
- Porsche 964 (911) TURBO 3.6L 1991-93
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
O-Ring Seal 18 x 2.5mm
Sold each
On Porsche 911 models from 1984–1986, it is used in the
gearbox oil cooler assembly. On Porsche 964 and 993 models, it is used for the
heater box water drain pipe.
Fits:
- Porsche 911 1984-1986 3.2L
- Porsche 964 (911) C2 1989-93
- Porsche 964 (911) C4 1989-93
- Porsche 964 (911) RS 3.6L 1991-93
- Porsche 964 (911) RS 3.8L 1991-93
- Porsche 964 (911) TURBO 3.3L 1991-93
- Porsche 964 (911) TURBO 3.6L 1991-93
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) RS 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) GT2 1994-97
- Porsche 993 (911) TURBO S 1994-97
Diagram Ref No 6 or 19
What Does It Do?
The O-ring creates a seal between adjoining components, helping prevent unwanted leakage.
In the gearbox oil cooler application, it helps maintain an oil-tight connection. In the heater box drain assembly, it helps seal the relevant drain pipe connection.
Why Does It Fail?
Common causes include:
- Rubber hardening with age
- Exposure to heat and temperature changes
- Compression and loss of elasticity
- Cracking or splitting
- Damage during removal or installation
When Should It Be Replaced?
Replace if the O-ring is brittle, flattened, cracked or damaged.
Replacement is recommended when dismantling the gearbox oil cooler connection or heater box water drain pipe, particularly where the original seal has deteriorated.
Checks & Installation
Inspect the sealing groove and mating surfaces for dirt, corrosion or damage.
Ensure the replacement O-ring is correctly seated without twisting or pinching. Check the connection for leaks after reassembly.
Key Features
- Replacement O-ring seal
- Dimensions: 18 x 2.5mm
- Fits Porsche 911 (1984–1986) gearbox oil cooler applications
- Fits Porsche 964 / 993 heater box water drain pipe applications
- Helps maintain leak-resistant connections
- Suitable for servicing and restoration
Porsche 911 / 964 / 993 Gearbox Oil Cooler & Heater Box Seals
The Porsche 911, 964 and 993 use rubber O-ring seals in various mechanical and drainage connections to maintain correct sealing and prevent unwanted leakage.
This 18 x 2.5mm O-ring is specifically used in the 1984–1986 Porsche 911 gearbox oil cooler and the heater box water drain pipe on Porsche 964 and 993 models.
Replacing deteriorated seals helps maintain reliable operation and prevent leaks during servicing or restoration.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99970714340
The product you are viewing cross references to these numbers
Porsche Gearbox Oil Coolers | Maintain Optimal Transmission Temperatures for Peak Performance
A gearbox oil cooler is essential for regulating transmission temperature and ensuring consistent performance under demanding driving conditions. By circulating and cooling the gearbox oil, it prevents overheating, protects internal components, and extends the lifespan of your Porsche’s transmission.
At Design911, we supply high-quality gearbox oil coolers engineered to meet or exceed original design standards. Built from robust aluminium and high-efficiency cores, our coolers deliver superior thermal management and fluid flow — ideal for both road and track applications.
Whether you’re servicing your Porsche, replacing a leaking cooler, or upgrading for enhanced performance, our gearbox oil coolers ensure reliable cooling and protection for every mile.
What Do Gearbox Oil Coolers Do?
The gearbox oil cooler dissipates the heat generated during transmission operation, maintaining stable oil temperatures for optimal performance and protection.
Core Functions:
- Regulates gearbox oil temperature to prevent overheating.
- Ensures consistent lubrication and hydraulic performance.
- Protects seals, bearings, and internal components from heat damage.
- Enhances efficiency and performance under load.
- Extends the overall lifespan of the gearbox system.
Without a properly functioning oil cooler, the gearbox can overheat — leading to fluid breakdown, gear wear, and costly transmission damage.
Why Do Gearbox Oil Coolers Fail or Wear Out?
Gearbox oil coolers operate under high pressure and extreme heat. Over time, these conditions can cause blockages, corrosion, or leaks that reduce cooling efficiency.
Common Causes of Failure Include:
- Corrosion or internal degradation from moisture or contaminated oil.
- Leaks caused by damaged fittings or cracked cores.
- Blockages restricting oil flow and heat transfer.
- External damage from road debris or impact.
- Deterioration of hoses and seals over time.
When an oil cooler fails, symptoms can include rising gearbox temperatures, oil leaks, fluid contamination, or transmission warning lights — all signs that replacement is required.
Why Replace Your Porsche Gearbox Oil Cooler?
Replacing or upgrading your gearbox oil cooler is essential to maintain safe operating temperatures, prevent gearbox wear, and ensure consistent performance. Performance-grade oil coolers are especially beneficial for track, towing, or high-torque applications.
Key Benefits:
- Restores efficient gearbox temperature regulation.
- Prevents overheating and oil degradation.
- Improves transmission longevity and reliability.
- Reduces thermal stress on internal gearbox components.
- Designed for Porsche 911, Cayman, Boxster, Panamera, and PDK models.
- Ideal for standard servicing, rebuilds, and performance upgrades.
Regular inspection and timely replacement of the gearbox oil cooler help maintain optimal performance and avoid major gearbox repair costs.
Highlights
- Premium Porsche gearbox oil coolers engineered for reliability.
- Efficient heat dissipation for manual, Tiptronic, and PDK gearboxes.
- Durable aluminium construction with high-performance cores.
- Prevents overheating and extends gearbox lifespan.
- Perfect for maintenance, restoration, or motorsport applications.
- Direct-fit replacements compatible with a wide range of Porsche models.
