Hi,

I recently rebuilt the a904 transmission of my '73 valiant and now I notice a slight humming sound in neutral.

The clutches, bands and bushings were changed. I did not touch the planetary gear set, because the end play was within specs. It shifts nicely and I only hear the hum in neutral. I can hear it when I am in the car, but not when I am standing next to it. After 2000 miles I changed the fluid and adjusted the bands. I noticed just a little bit of metal shining in the fluid.

This is the first automatic box I ever rebuilt, so I wonder if I missed something. But I might just be hearing things, as I finally managed to get the engine running very quiet. Is this something to worry about? Or is this normal?

Roelof

Anyone?

A slight hum in Neutral generally isn't much to worry about — it's often just a resonance from the hydraulic system. Turning the line pressure up slightly might eliminate it. But before you open up the transmission, check if it's actually the cooler lines vibrating. They run very close to lots of other parts, and even their slightest vibration can be highly audible inside the car.

In either case, you needn't worry about damage or reliability.

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Thanks Dan.

It's good to know I don't need to worry. It was the first time I rebuilt an automatic box, so was not so sure I'll check if something is resonating.

Roelof