2004 Pontiac Bonneville Trans Oil Pan Gasket Replacement Cost

Transmission pan gaskets are replaced once every 40,000-60,000 miles on vehicles with service intervals call for regular transmission fluid changes. Some automatic transmissions and CVT transmissions may be considered "sealed-for-life", but as these transmissions are gaining miles in the field, they are experiencing more failures due to lack of maintenance. Even these transmissions are being recommended for fluid and filter changes at normal intervals.

A leaky transmission pan gasket will be diagnosed at a glance, but replacing the transmission pan gasket can be for many reasons. There is no diagnosis needed when performing scheduled maintenance, repairing the transmission, diagnosing the transmission, or replacing the oil pan or filter.

The transmission pan is removed by removing all bolts surrounding the transmission pan. Before removing the final few bolts, any obstructions will be removed, and the pan will be allowed to tilt into a drain pan to lower the transmission fluid level. The transmission pan gasket will be peeled away as the pan drains, and the transmission fluid filter will be removed simultaneously, using the leaning transmission pan to catch the filter, gasket and all the fluid that will be falling from the transmission. Once the transmission is done draining fluid, the technician will clean the pan, the lower valve body, inspect for obvious signs of failure or future trouble, and checked the fluid, magnets, and filter for debris. If everything is satisfactory the technician will clean the mating surfaces of the transmission and transmission pan, replace or reuse the gasket, instal a new filter, and instal the transmission pan with locking compound on the threads of the transmission pan bolts. Once complete, the transmission will be filled, warmed by running the engine, and topped off with transmission fluid

We recommend using a one piece synthetic gasket where silicone is not recommended. Even on models which originally used a cork gasket, the rubberized synthetic gasket has far superior sealing and adhesion properties, and may even be re-useable.

Modern vehicles with drain plugs in the transmission drain pan should be referenced before engaging in servicing the transmission at home. More frequently, manufacturers are using transmissions that must be filled from underneath the vehicle with a pump. This means that a leaking transmission pan gasket change may require the vehicle be taken to a service center.

This job requires a little bit of finesse, and most DIYers will split their first transmission pan gasket when installing the transmission pan. That is because the transmission pan should be installed with a small torque wrench, all bolts tightened in sequence, and by placing trust in the manufacturers light torque specifications. Again, if the pan is filled through a combination drain and fill plug in the bottom of the transmission pan, only the advanced DIYer capable of monitoring the transmission temperature sensor via data link should attempt this repair.