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Wed Jul 23, 2014 10:00 pm

My '91 Westy's GW rebuilt auto transmission makes a high pitched humming sound while in reverse, but not always. It's unpredictable, but it's usually when backing up a slight incline. The sound is difficult to describe: a humm; a whine; a moaning sound; a soft whistle; a little like the beeeeeep-beeeep-beeep sound trucks make built into their systems to warn others, but mine is just a steady high pitched oooooooooooh. One steady pitch. Ocassionally it makes a single beeeeeooooop sound right after it starts, in park. GW says they've never heard of the problem. Other mechanics say the same thing. One more thing: I get a clunking sound when it shifts down into 2nd and the same sound when letting off the gas at low speeds; each time I lift of gas it immediately clunks, like there is something slipping. Transmission or CV joint?

Any help? Any ideas? Anyone had this problem?

Thanks in advance.

More: it got new motor mounts 25k miles ago and made humm right after rebuilt went in. Humm is erratic. No humm when backing downhill; only on flat or slight incline. Sound/noise/whine/humm/high pitched whistle, is always same tone, same level.

Surfing

Wed Jul 23, 2014 10:30 pm

Steady tone always? Does not change with vehicle speed? Most transmissions use the 1st gear in reverse so it makes a whining sound under load beacuse it's turning backwards, but it will change pitch as speed increases/decreases.

Clunk may be a worn or broken rubber trans or motor mount.

Fri Jul 25, 2014 12:55 am

I REALLY get that noise in reverse only! but not all the time. I think mostly just when its cold.

quite high, constant pitch, really bizarre.

I never bothered to diagnose it, I just don't go far or fast in reverse!