Transmission Seals & Gaskets

Fluid leaks are one of the most common transmission problems. But while the stains they leave on your driveway or garage floor are annoying, the consequences of leaking fluid are much more serious for your transmission. All transmissions are designed to operate with a fluid capacity that ensures optimum performance and reliability. Transmission fluid lubricates, cools, and in automatic transmissions enables transmission operation. A leak will reduce the fluid quantity in the transmission, and if the leak goes unrepaired and the fluid level is not checked and replenished, the transmission may suffer damage and deliver poor performance. If your transmission is leaking, we have the gaskets, seals and O-rings to restore proper fluid retention and long-term performance and durability.

Transmission fluid lubricates internal transmission components. During operation, the extreme pressure between gear teeth creates heat, and transmission fluid also cools the transmission. The fluid’s cooling function is essential on automatic transmissions, because in addition to gear pressure, the friction in clutches and bands creates heat, and therefore vehicles with automatics are equipped with external fluid coolers to transfer heat from the fluid to the air passing through the cooler. But in addition to cooling, transmission fluid has another indispensable function on an automatic transmission because it is the medium that provides the hydraulic force for transmission operation. Low fluid level due to a leak could cause reduced lubrication and cooling capabilities, resulting in accelerated wear and overheating, but it could also cause poor performance and damage from reduced hydraulic pressure and clutch and band slippage.

Common manual transmission leak points include the case-to-extension housing gasket, side cover gasket, shift lever seals, input shaft seal, input shaft bearing retainer gasket, and speedometer gear housing O-ring. Automatic transmissions can leak at the fluid cooler line connections, line and governor pressure plugs, case-to-extension housing gasket, oil pump seal, oil pump-to-transmission case seal, dipstick tube seal, governor cover, servo cover, manual shaft seal, vacuum modulator O-ring, and throttle valve cable seal, but one of the most common leak areas is the transmission fluid pan. The extension housing seal is another commonplace source of a leak on both manual and automatic transmissions, as are the axle shaft seals on manual and automatic transaxles.

Some points to consider when attempting to repair a leak: Some shafts are supported by bushings to stabilize the shaft during operation and prevent excessive play and vibration. If the bushing is worn, installing a new seal may not fix the leak. An extension housing seal that prevents fluid from leaking past the driveshaft slip yoke is an example. If the extension housing bushing is worn, the slip yoke may not be centered in the bore, making it difficult or impossible for the seal to do its job. The extension housing bushing must be replaced along with the seal. Also, some shafts can become worn and grooved from long-term seal contact, and again, merely installing a new seal most likely won’t repair a leak. We offer a variety of repair sleeves. The sleeve is thin yet strong and is a press fit installation over the shaft. When it’s in place the seal lip has a smooth surface to contact for proper lubricant retention.

The source of a transmission leak may be difficult to locate. Begin by making sure what’s leaking is transmission fluid. Automatic transmission fluid is red when it’s fresh but darkens with use. Manual transmission fluid can be red or dark brown, since depending on year and model, the vehicle manufacturer may specify automatic transmission fluid or gear oil. If a careful visual inspection doesn’t reveal the source of a leak, clean the exterior of the transmission with a suitable degreaser, then operate the vehicle and again check for leaks. If the leak is still not evident, add fluorescent dye to the transmission fluid, then run the vehicle to mix the dye with the fluid. The dye will leak along with the fluid and be visible with UV light. We can supply you with the dye and a leak detection flashlight.

No matter what kind of vehicle or transmission you’re working on, we have the replacement transmission seals, gaskets & O-rings to make your gearbox leak free. However, automatic transmissions require more than external sealing. To develop the proper amount of hydraulic pressure for optimal shifting and transmission performance, a variety of gaskets, seals and O-rings are required for internal transmission components and you’ll find them all here on our digital shelves. All our transmission seals, gaskets and O-rings are manufactured according to original equipment specifications, so when service is completed you can count on the performance and reliability your vehicle was designed to deliver.