Transmission Slip on a 1990 Toyota Camry

In our Ask a Mechanic forums, returning mechanic tomcat4343 asked about the automatic transmission on a 1990 Camry. Tom is an experienced DIY mechanic, but is not familiar with automatic transmissions.

The problem is that the transmission, once warmed up, does not shift and often leaves the car stranded.

To begin with, the first thing to do is check the fluids. This is standard fare on any suspected mechanical issue like this. With an auto-trans, the fluid is extremely important (and separate from engine oil). It should not look "burnt" or have flakes in it.

Next, check the car's maintenance intervals and history to be sure transmission maintenance has been done properly. In Tom's case, the car has no history and appears long overdue for a transmission flush.

Because it's so far gone, however, master mechanic Big Block 409 was right to immediately caution Tom not to flush the transmission as that could lead to blockage that would seize the gears and lead to much, much worse problems. Instead, a normal "dump and replace" was recommended.

This is simply emptying the transmission of its fluid, removing filters/screens, and then replacing all with new. No power flush or other method of "pushing" the old fluid through is done, leaving some of it behind.

Finally, using genuine original equipment manufacturer fluids and filters (in this case Toyota) is highly recommended.

A transmission dump-refill is something most home mechanics can do easily on their own.