W163 Ml270 noisy in reverse gear

[MOZ]

Hi,
I need some experienced opinions/advice.
Tonight as the Mrs reversed off the drive I heard a noisy squeaky once or twice per revolution sqeal .
It sounded vey much like a metallic type of squeak/scrape . At first I thought it was a brake type noise and then possibly suspension as it squeals.

I took it for a good drive and can hear nothing when in drive, but the sound is there immediately when in reverse and moving ( no sound when in reverse but stationary) and is definitely once per Rev and the noise is speed dependent.

I tried reversing down a hill in neutral ( riding on the brakes) and using reverse gear. Unfortunately the noise is related to it being in reverse gear !! And no noise when rolling backwards in neutral.

So any thoughts, I have done some searching and a lot of things come up possibly suggesting center support bearing, but if it were this would I not still hear it when in neutral? ( I guess it would be loaded differently , but would still rotate).
Or is it my worst fear and maybe a dying gearbox?

I don't have a transmission dipstick to check fluid level (ATF) but will get one ASAP and check ( the ATF was changed about 18 months ago) and not noticed any leaks.

Any similar experience or thoughts out there. Certainly sounds expensive.
Thanks
Moz





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[MOZ]

Fixed!:bannana:
Turned out to be a dry and sticky prop-shaft Universal joint.

There is no noticeable play in it but also no real lube around it.

Prop-shaft removed, UJ manually worked hard and well lubed back up and then replaced, noise completely gone.

Will keep an eye on it and replace it once I start getting play in it but a lot happier now.

I wasn't too worried about the type of noise (loud rotational squeal - like brake squeal or squeaky suspension) just worried that it only appeared when reverse gear was engaged (not there when freewheeling backwards - even though the prop shaft was still moving) and the fact it wasnt there in forward gears which mad me worry it was gearbox related . I assume it is just the additional resistance and load on the shaft when the gear is engaged that made the difference.

Much happier man now, hope this helps someone else in the future.

Moz

 

[Tattmaylor]

I’m going to test this theory on my SL tomorrow. Squeaks like mad in reverse (worse when it’s cold outside) which I’ve always thought was brake related, but several mechanics can find nothing wrong with the brakes, and squeaking in reverse only just seems odd.