A transmission gasket leak will show up as either red droplets on the pavement for vehicles with an automatic transmission, or oil spots for vehicles with a manual transmission. Small leaks can be maintained by continuing to add either transmission fluid or transmission oil with no harm to the transmissions. But larger leaks must be attended to before the transmission runs out of fluid and is damaged. A permanent solution is to take your vehicle into a professional transmission repair shop, pay the expensive repair bill, and allow them to replace the leaking gasket. But there is an alternative cost-effective measure that any do-it-yourself person can do.
Open the hood of your vehicle, and locate the transmission fluid fill tube. On most vehicles, where the the transmission fluid dipstick resides is the fluid fill tube.
Remove the fill tube cover and pour in a bottle of transmission stop-leak, per manufacturer's instructions.
Replace the dipstick into the fill tube, and close the hood. Monitor your transmission fluid level for the next 1,000 miles to ascertain if the leaking has stopped. Minor gasket leaks will be sealed with this method, but serious leaks must be professionally repaired.
Jack up the car with a standard vehicle jack, and place jack stands beneath the frame to secure the vehicle. Place wheel blocks behind the rear wheels.
Locate the fill plug on the manual transmission. It will be approximately halfway up and on the side.
Remove the fill plug with a wrench, and place it off to the side.
Add in the recommended amount of stop leak or oil stabilizer. Most of these products come with elongated nozzles to fit in the filler hole. Simply squeeze the required amount into the transmission. For bottles of stop leak, a small funnel can be inserted into the hole, and the stop leak can be poured into the funnel.
Screw in the filler plug firmly, remove the jack stands and jack down the vehicle. Minor gasket leaking will be repaired with an oil stop-leak additive or oil stabilizing product, but serious leaking will need professional repair service.
