BA Falcon Drone noise from Rear (Annoying arrhhhh)

[RS-11]

Hey gang,

Just got a issue with my daily driver BA falcon.
Lately I have been getting this drone coming from the underneath of the car - I think its towards the rear.
It almost sounds like a tyre drone noise but its not for the reasons below.

It does not do it when I start the car or rev it in neutral. As I was thinking it was a muffler / exhaust problem at first, but I have even had it up on the hoist at a muffler place and seems all good to the guy there and it would usually do it revving in neutral.
Anyways it really only makes the noise when the car is under load / acceleration. Don't really hear it too bad at highway speed as usually not accelerating hard once at speed. But around town it is real loud, I can hear it best when coasting at around 40 klms/hr and then accelerating a little.
It is most noticeable to me around the 1000 rpm - 2000 rpm range. I don't have to accelerate hard just touch the accelerator is starts droning then if I lift off it goes away and so on.

I was thinking it must be drive-line. I was thinking diff, but I thought that that usually only makes noise going round corners if it bad and my car makes no noise around the corner unless i have the accelerator down like mentioned previously. My next step was to change the diff oil and see if that helps... don't think its been changed in a long time..

Anyone heard of anything like this before.. could it be diff / gearbox / drive-shaft??? I am a little confused. The car still seems to drive fine, but I just want to sort it out before the car brakes down on me somewhere.


Also while I am on the subject of noisy falcon. The only other thing wrong with the car is the usual BA Falcon "clunk" from the back of the car. I had a look under there and it seems as though the Main Diff bush is shagged like usual. Has anyone tried to change these before. I read that you need a hoist and takes 3hrs.... as I have no hoist i was thinking of stumping up the cash for a pro to sort out. Would be $500+ I would imagine... could i just leave it like everyone else, will it cause any major problems?

Any thoughts would be great.
Cheers guys

[tut]

diff whine can happen in a straight line, and is dependant on load.

[pottery beige]

diff centre will flap all over the place with fucked diff bushes, pinion angles, will whine and drone all sorts of shit..

[RS-11]

diff centre will flap all over the place with fucked diff bushes, pinion angles, will whine and drone all sorts of shit..

That did cross my mind.
That changing the oil may be futile if the angles are all screwed up.

I just dismissed it as I have heard the clunking diff bush before without droning in other BA Falcons. But I guess mine could be a bit more damaged.

[GTREA]

Common problem, Pinion gear teeth are worn.

Diff rebuild required to fix the problem.

Diff will not explode, you can continue to drive, but noise will stay.

Could also be the Bearings, but as above.

How many K's does it have on it?

Have you ever ridden in a Taxi?

[RS-11]

Not a huge amount of klms -- around 155,000
Yeah taxis make a bit of noise, try not to use them too much.

The clunking does not bother me too much as I know what it is. Also it is only there at low speeds around down and when going over bumps. When on the flat highway the noise goes away. The droning noise does get annoying though.
I was having a look this morning at the diff and I can see its hanging a little off the main bush.

Btw... Is the filler point for the diff just at the back of it near the top just above the axle -- drivers side... I think it was a 13mm... I could see it coming from the back of the car.
Prob not much point changing the diff oil I guess.... although I have heard miracle stories

[Glenno]

Worn diff for sure.

Diff bush replacement is a 3 hour job as the whole rear K frame has to come out (diff sits on top), as well as a shagged bush it is pretty common for the bolt to break so have a look at the Superpro bush kit and Unbrako bolt option.

Filler plug is a pretty big size (27mm AF ?) and in a painful spot. When the rear bush goes and the bolt breaks the pinion flange can contact the fuel tank and rub a hole in it so don't leave it too long.

[RS-11]

Worn diff for sure.

Diff bush replacement is a 3 hour job as the whole rear K frame has to come out (diff sits on top), as well as a shagged bush it is pretty common for the bolt to break so have a look at the Superpro bush kit and Unbrako bolt option.

Thanks
Probably not much point in changing the bush if the diff is worn... I should prob just wait for the diff to need changing.

[RS-11]

hmmm im looking at the wrong plug...

[Glenno]

Diff plug is on the bottom right of the photo the breather pipe is partially covering it in this photo.

[RS-11]

cool man cheers.
I might just get the bush fixed and change the oil (prob at a shop as it sounds like a big job and then just put up with the noise if it wont go away until i need a new diff)

I should probably get a tranny cooler soon as well as I believe the BA's even my MKII are notorious for shitting gearboxes.

[willsy01]

Wife/girlfriend is sitting in the back. Tell them to GTFO.

[RS-11]

nah man that is more of a whiny / moneygrab - wallet opening noise... this is a drone like you mum lol

[Spoonfed]

Clunk/bang = diff bush. flogged diff bush = harmonics/drone transmitted through car on load acceleration.

[Pol Pot]

I should probably get a tranny cooler soon as well as I believe the BA's even my MKII are notorious for shitting gearboxes.

More the radiator shits itself, and the transmission is cooled through the radiator, then your trannie fills with coolant which fucks it very quickly. Dumb arse Ford design. But yeah, do it.

BA diff whine is very common..

[RS-11]

Hi guys,

Regarding the bush update.
The problem I have is most people are saying that they check there diff bush and see that its busted. But I look at mine and it seems different. If you have a look at the picture it has this metal funnel looking thing coming out of the back of the bush. I look behind that and its a bolt heat, washer and the rest of it is brown. It all looks ok.

Or do I look in between the funnel thing and the suspension cradle where I think the diff bush is?? But even with a torch and mirror this seems very hard to do. I must be doing something wrong as other people seem to check theirs easy,

I am keen to do the bush the easy way through the spare wheel area. As I have seen a sweet guide that allows you to do the job in 30 minutes without a hoist and lowering the cradle.
But I don't want to cut it open if there is no need. I took it to a suspension / mechanic place and they said the bush looked fine, but I am not convinced. They did show me when it was on the hoist that my rear wheels were wobbling a bit and I am booked in to get a few bushes in the rear suspension that they said would stop this. They seem to think that is the clunk, but im not sure that would make that diff droning noise.

Pic of underneath.
http://i1141.photobucket.com/albums/...x-33r/diff.jpg

Thanks gang.

[RS-11]

Looking at another photo, I think the round thing at the back may be a Harmonic Damper. Still cant work out how to check the bush in between well though.

[Glenno]

The round thing at the back is a counterweight, you can get rid of it when you change the bush. The bush is in the K frame between the counterweight and the diff.

[RS-11]

The round thing at the back is a counterweight, you can get rid of it when you change the bush. The bush is in the K frame between the counterweight and the diff.

Cool. Thanks mate
Is there a way to check it without puling it out??
As it is pretty drastic to change. Maybe i'm looking from the wrong angle.

[Glenno]

Yeah use a big lever and try and move it around, if its stuffed it will have freeplay if its ok it will just feel like a rubber bush.

[RS-11]

Yeah use a big lever and try and move it around, if its stuffed it will have freeplay if its ok it will just feel like a rubber bush.

Cheers mate,
I'll check it out tomorrow thanks