Loud whine at a steady speed, diff, gearbox or what?

[aww999]

Hi guys, had my Fury out on track recently with 888s on it, I was getting the power down much harder and much sooner than on the previous crappy tyres and it seems the increased forces being transmitted have damaged something.

The car still feels normal to drive, but I am getting a loud whine which varies with road speed. It comes in at about 20mph, and gets louder all the way up to 80ish (didn't go any faster than this but I doubt it would get quieter again!). It is very loud at a steady speed, gets a lot quieter when accelerating, and goes away completely on a trailing throttle. It also seems to be louder in right hand corners, and sounds like it is coming from the left rear of the car. It doesn't seem to change whether I am in third, fourth or fifth, and all the gears engage cleanly.

My guess is the diff, it is a live axle (escort I think) with open diff, probably all standard parts in there from when the kit was built in the 90's. Are there any tests I can do to confirm the source of the noise before I start ordering new parts? I was thinking of jacking it up and maybe checking for freeplay rotating one wheel against the other, or against the propshaft, but I don't know whether this would tell me anything useful. Would I be better off taking the backplate off the diff, or pulling the whole unit for examination on the bench?

I can take the thing to bits with no problems, but I have never had to fix a diff problem before (if that is what's gone wrong!) so I don't really know what I'm looking for...any advice much appreciated!

[Paul.B]

Have you checked the rear wheel bearings? If it sounds like it is coming from one side you may have a shot bearing. Trouble is these noises seem to move about in your head! Jack the rear of the car and feel for play in both rear wheels.
It would be a lot simpler and cheaper than the diff so worth checking first.

Good luck

Paul.B

[Russ Bost]

In addition to last comment, if it doesn't vary with which gear you're it's going to be diff or wheel bearing - wheel bearing is far more likely, jack that corner up & spin the wheel listen for a slight hum/whirring noise & compare to the other side. As said a wheel bearing is much cheaper than a diff, if it was a RH circuit then n/s/r bearing is most likely if noise is defo from the rear.

[Ferg]

In my experience you can feel wheel bearing rumble with one finger on the spring when you spin the wheel.

[dean100yz]

Yeah Id like to say wheel bearing but I gotta say it sounds like your diff. I got a Escort live myself and its started whinning at constant speeds say 50-70. Dont think mines as bad as yours. It doesnt make any sound when gassing it through the gears

[kwosimodo]

Id put my money on rear wheel bearing, especially when the noise changes on cornering.

[aww999]

Thanks for all the responses guys. I have just been out to the garage, I can't feel any play in the rear wheels. I have taken the wheels and the brake drums off, and put a stethoscope on what I assume is the wheel bearing housing (just inside the axle flange with the wheel studs in it). No sound from here either when the axle is spun by hand.

Although the noise varies slightly when cornering very hard, it goes from LOUD to silent when coming on and off the throttle.

Any more advice would me appreciated, but I am fearing the worst and off to scour the net for an axle rebuild manual...

[tr7v8]

Sounds like Diff pinion bearing to me. If it i noisy under power & quietens when you come off the power it sounds like pinion bearing.