Whine at motorway speed?

OrangeBobTail · Aug 19, 2013

Morning all,

Just come back from a 400 mile round trip weekend on the south coast. On the last M25 stretch I noticed its developed a bit of a whine seems to start at about 45mph as a hum, by 65 its medium pitched quite loud whine and at 85 its quite high pitched almost a scream, but on overrun it almost disappears, put some power on or enough to hold speed and the noise is back, it seems to be coming from the rear but a bit difficult to say for definite...

All fluids (diffs, swivel housings, transfer box, auto gearbox & engine oil) were changed 5 weeks ago, old fluid wasn't too bad, metal dust stuck to the magnets but nothing else.

Its going to be a few days before I can get under to start investigating, any ideas what the most likely culprit would be, and how to test?

Disco 1 ES '97 3.9 V8 Auto factory standard at present.

Thanks

Dave

thebiglad · Aug 19, 2013

OrangeBobTail said:
Morning all,

Just come back from a 400 mile round trip weekend on the south coast. On the last M25 stretch I noticed its developed a bit of a whine seems to start at about 45mph as a hum, by 65 its medium pitched quite loud whine and at 85 its quite high pitched almost a scream, but on overrun it almost disappears, put some power on or enough to hold speed and the noise is back, it seems to be coming from the rear but a bit difficult to say for definite...

All fluids (diffs, swivel housings, transfer box, auto gearbox & engine oil) were changed 5 weeks ago, old fluid wasn't too bad, metal dust stuck to the magnets but nothing else.

Its going to be a few days before I can get under to start investigating, any ideas what the most likely culprit would be, and how to test?

Disco 1 ES '97 3.9 V8 Auto factory standard at present.

Thanks

Dave

Hi Dave, before spending any REAL money I would be checking the oil level and quality in the diffs and transfer box. Did you do the oil changes before your trip or a garage?

If it was a garage, I would change them all myself. You will need 6 ltrs of EP 80-90 to GL4 or 5 spec.

I would also check the condition of the propshaft U/j's and the rubber doughnut for wear and give the U/j's a good greasing.

Dave

Paul D · Aug 19, 2013

Ditto to tbl .. 'specially the UJ's and donut. .. Also check tyres for pressure and wear, especially uneven wear.

RKServicing · Aug 19, 2013

I'd bet your rear diff if from rear. Mines done the same last big journey. Was barley any noticeable play in it but as I have a few spare I swapped it over and boom. All fixed.

discool · Aug 19, 2013

Doughnut? the OP has a 1997 V8 auto.

Paul D · Aug 19, 2013

discool said:
Doughnut? the OP has a 1997 V8 auto.

Do they not have donuts on the rear prop then?

bencorkill · Aug 19, 2013

Paul D said:
Do they not have donuts on the rear prop then?

Mine does

Paul D · Aug 19, 2013

I thought they did .. the manual doesn't say a difference between rear shafts.

OrangeBobTail · Aug 19, 2013

Thanks guys,

Nope no rubber donut on mine. I'll defiantly check the UJ's, that would be an easy fix :-D

Yes it was me that did the oil changes, I used the correct spec oil as per the manual, no offense to anyone but I've had some bad experiences with garages...

RKServicing: I'm not too far from Bicester, if it is the diff might you want to sell me one?

Dave

RKServicing · Aug 19, 2013

OrangeBobTail said:
Thanks guys,

Nope no rubber donut on mine. I'll defiantly check the UJ's, that would be an easy fix :-D

Yes it was me that did the oil changes, I used the correct spec oil as per the manual, no offense to anyone but I've had some bad experiences with garages...

RKServicing: I'm not too far from Bicester, if it is the diff might you want to sell me one?

Dave

I normally would but we've just used the last two 4 bolt ones. On the tray back. (Removed locking diffs).

We buy good second hand ones from a chap called dan... I'll pm you his mob no.

discool · Aug 19, 2013

Paul D said:
Do they not have donuts on the rear prop then?

Nope, but did return on 1998MY onwards V8 discos I believe.

My old RR had one but never had any trouble with in the 10years and 100,000 miles I owned it, the issues with them must be a diesel disco thing.

thebiglad · Aug 19, 2013

I think we are getting off track here focussing too much on "rubber doughnut or not" as this is less likeyl to be the cause of the whining, isn't it.

OrangeBobTail · Aug 26, 2013

As it was dry I had a good look under the motor today, defiantly no rubber doughnut, prop shaft UJ's look in good condition, no slop in them, also greased them up whilst I was there. Front diff looks good, almost no play there. The only play I can find is in the rear diff & the transfer box, the rear diff looks like its had fluid coming from the input shaft seal so that will need replacing.

Any idea what the most likely culprit is now, should I change the rear diff for a known good one? Do the transfer boxes whine & fail?

Thanks

Dave

jamesmartin · Aug 26, 2013

try it with each prop off in turn , diff pinion bearing noise appears on over run diff carrier bearings on power ,diff play is in up/down in/out not rotational you check for noise/leak issues,prop ujs can seize and have no noticeable play you need to remove one end of prop to check

thebiglad · Aug 26, 2013

Hi OBT, can't remember and didn't have time to read the thread, have you changed all oils in trans box main gear box and diffs?

Dave

OrangeBobTail · Aug 26, 2013

jamesmartin said:
try it with each prop off in turn , diff pinion bearing noise appears on over run diff carrier bearings on power, you need to remove one end of prop to check

Its defiantly worse with some power on. No probs I'll drop the prop shafts and test properly.

thebiglad said:
Hi OBT, have you changed all oils in trans box main gear box and diffs?

Yes I changed diffs, swivel housings, transfer box, auto gearbox & engine oil my self. Although rear diff was proper manky when it came out...

Thanks

Dave

jamesmartin · Aug 26, 2013

take vehicle for a run when you only have one prop in turn

OrangeBobTail · Aug 26, 2013

jamesmartin said:
take vehicle for a run when you only have one prop in turn

Really? I don't want to destroy the transfer box... I take it you have to put the diff lock on?

Thanks

Dave

jamesmartin · Aug 26, 2013

OrangeBobTail said:
Really? I don't want to destroy the transfer box... I take it you have to put the diff lock on?

Thanks

Dave

yes in diff lock ,how would t/box damage occur ?its a fairly common diagnostic technique amongst those with any knowledge

OrangeBobTail · Aug 26, 2013

jamesmartin said:
how would t/box damage occur ?its a fairly common diagnostic technique amongst those with any knowledge

Yeah, thinking about it logically it should be fine. Sorry I didn't mean to doubt you, it just seemed a little severe... No probs I'll give it a go. If it whines with front prop shaft removed then its rear diff, if it whines with rear removed then its front diff, if it whines on both tests then its transfer box?

Thanks

Dave

Whine at motorway speed?

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