... when I use the washing machine. The gas dryer works fine.
I have replaced the GFI plug-in, but the problem persists.
The washer is fine when I run an extension to another circuit.
What can I do?
Thanks.

First, I question why you replaced the GFCI receptacle. Was it constantly necessary for you to re-set the receptacle?

Is the problem that the circuit breaker is tripping only when the washing machine is in use or do both the washing machine and dryer have to be in use.

To be honest with you, my immediate suspicion is the motor on the washing machine demanding too much current (amperage) and tripping the breaker.

How old is the washing machine and how heavy of a duty cycle is it used for?

Was the circuit you plugged the extension cord into GFI?

Sometimes motors and GFIs just don't play well together.

Don: He said the GFI is tripping.

First, I question why you replaced the GFCI receptacle. Was it constantly necessary for you to re-set the receptacle?

Is the problem that the circuit breaker is tripping only when the washing machine is in use or do both the washing machine and dryer have to be in use.

To be honest with you, my immediate suspicion is the motor on the washing machine demanding to much current (amperage) and tripping the breaker.

How old is the washing machine and how heavy of a duty cycle is it used for?

Well, I guess I wasn't clear.
The GFCI receptacle kept tripping, not the breaker at the panel. I thought the GFCI was old and/or faulty, so I replaced it.
The washer alone trips the GFCI, in either plug-in. It happens as soon as I start the washer, with no real load on. The beginning of the cycle is just filling the tub, and it still trips the GFCI.
The washer works fine when plugged into another receptacle which is not GFCI.
The washer is about 10 years old, and is not a super heavy duty machine.
Thanks for any more help.

To me that indicates a small leakage somewhere and the GFI is doing its job. Probably in the water valve or that circuit. Try skipping the fill cycle and see what happens.

To me that indicates a small leakage somewhere and the GFI is doing its job. Probably in the water valve or that circuit. Try skipping the fill cycle and see what happens.

That makes sense, except the GFCI trips in ANY cycle, at any point in the cycle - fill, agitate or spin.

Certainly sounds like you have leakage some where. I have no idea about how you would go about finding it. You could open the washer and look for moisture somewhere on electrical parts. You could use a hair dryer and try drying every thing but if there is moisture, it may be inside some electrical part.

This question needs to be moved to the appliance repair forum.