Hi All, first few drives of my r1 engined mnr this year were all going well until I noticed the diff sounds like a fuel pump whirring at low speeds. Any ideas on what this could be and any ways to diagnose the fault, or is this a certain sign of a rebuild and I should stop driving it?
Thanks in advance
Adam

Check the oil level is the easiest thing to do first!

My diff has had a very slight hiss since I built the car, it's got no worse in 10 years

The first time I drove my car without ear protection I thought my diff was about to pack up! In the original Escort the diff was separated from the driver by the body shell, plus all the carpet, seating and sound-proofing, but without all that in the way I was hearing the gears whirring in all their glory.

It's been like that for 10 years - I've got used to it...

Funny how relevant posts pop up.

I had my daughter out for a run the other day and killed the ignition whilst free wheeling down a slope so i could talk to her. Thought my fuel pump was still running behind me. Checked I'd switched off and realised it was the diff. Wondered if it was a problem but figured it's always been like that, i just thought it was the pump.

Thanks for the thoughts all. I'm only concerned as it was never there before. It's definitely a whirring slight hissing kind of sound. Will try an oil top up first and see where I get to.

When I solidly mounted my celica rear diff it whinned really bad. Before the worn rubber mount made no noise.
So rubber mounting the diff will stop the noise to an extent.