Rear Diff, Viscous Coupling HELP

adamrharding · Jul 13, 2010

Hi all

Towing home horse trailer from 10 miles away and started getting thudding type noise which sounded to me like something rotating on the axle. Stopped, had a look underneath, but nothing there... still happening but got home about 10:00pm so left it until morning.

07:00 up nothing underneath still, all quiet up to 20 MPH, then thudding comes back directly related to road speed, permanent knocking then. Dropped clutch to prove not engine, left on extended height overnight with tailgate open, no sagging. So got the kindly AA to take it to my indie who diagnosed a broken rear diff (RD), and suspect Viscous Coupling (VC).

Reading Ashcroft transmissions site they say an easy test for dodgy VC is if your wheels "chirrup" or "squeal" going round corners, mine has been doing this for a while on painted surface inside local multi-storey, other cars do it so I thought it was just lack of grip causing the noise?!?!? Or am I barking up the wrong tree? Anyone else have any ideas???

Annoying thing is that last Thursday it flew through the MOT

RD £285, VC £295

plus VAT and fitting.

Thanks in advance.

Adam

fanatic · Jul 13, 2010

sounds like transfer box chain if you have a p38.
You can tell if viscous coupling gone-full lock on normal tarmac-not car park-will chirp or you can feel it not turning smoothly

adamrharding · Jul 13, 2010

Fanatic, thanks

Garage suspect the VC caused the rear diff problem, but will look into it more tomorrow. Looking on Ashcroft's site again, I have the Borg-Warner transfer box, I think, so they just need to remove the transfer box, dismantle, remove chain, refit new chain and reverse procedure. A long and complicated job??

Is that a weak point of the BW box, the chain? It is a 158k miles car.

Thanks again

fanatic · Jul 13, 2010

Others on here have suffered stretched chain in transfer box not a major drama.

If your getting a thud, thud noise it is possible the chain-worth checking out as a possible

adamrharding · Jul 13, 2010

Fanatic, thanks again.

Will tactfully suggest to garage.... well I'll try to.....

Datatek · Jul 13, 2010

The thudding noise could be something as simple as a propshaft UJ worn. You can test the VCU by jacking one front wheel and trying to turn it, it should be just possible with a lot of effort. If it doesn't turn at all then the VCU is seized. If the VCU is seized, then it will eventually break a diff, usually the front one, due to transmission wind up.

adamrharding · Jul 13, 2010

Datatek said:
The thudding noise could be something as simple as a propshaft UJ worn. You can test the VCU by jacking one front wheel and trying to turn it, it should be just possible with a lot of effort. If it doesn't turn at all then the VCU is seized. If the VCU is seized, then it will eventually break a diff, usually the front one, due to transmission wind up.

Datatek, garage are telling me rear diff is definitely knackered but suspect the VC's caused it. The AA man jacked the front up and could move the wheels, just.

If not the VC, then would the transfer box chain cause it? Or is some other problem lurking out there?

Thanks in advance

Datatek · Jul 13, 2010

adamrharding said:
Datatek, garage are telling me rear diff is definitely knackered but suspect the VC's caused it. The AA man jacked the front up and could move the wheels, just.

If not the VC, then would the transfer box chain cause it? Or is some other problem lurking out there?

Thanks in advance

If your AA man had both front wheels off the ground, he did not check the VCU, it's one wheel off. The Transfer box chain would not knacker the diff. Never trust a garage, how did they check the diff? Could be a half shaft gone for instance. Have they removed the diff to check?

adamrharding · Jul 13, 2010

Datatek, Indie Landy specialists have been good to me so far, were checking my machine out around jobs they had booked in, more time to look tomorrow. Lead mechanic passes on messages to reception, she told me the rear diff is definitely knackered. They are due to remove diff tomorrow. Then hunt around for cause.

Fingers crossed it's something cheaper/simpler

Thanks

kooky_guy · Jul 13, 2010

As has been mentioned already a seized VC is likely to damage the front prop and diff not the rear.

Ashcroft suggest the transfer box chain only lasts 100k miles but that wouldn't damage the diff either. Could just be one those things. Everything breaks eventually!

Guy.

wammers · Jul 13, 2010

adamrharding said:
Datatek, Indie Landy specialists have been good to me so far, were checking my machine out around jobs they had booked in, more time to look tomorrow. Lead mechanic passes on messages to reception, she told me the rear diff is definitely knackered. They are due to remove diff tomorrow. Then hunt around for cause.

Fingers crossed it's something cheaper/simpler

Thanks

Your rear diff is possibly just worn out with towing. If you have a seized viscous coupling it will affect the front diff long before it hurts the rear one.

adamrharding · Jul 13, 2010

Thanks Wammers, Kooky and Datatek again,

Have only owned car for one year come Aug, and towed maybe 3 tonnes for 10 or so days since, so heavy and up and down hills in Wales, but not often. Man i bought car off owned car since 6 months old, and not towed with it. It is a 96 plate Manual Diesel. I suppose that suddenly giving heavy wear and tear could have damaged an old part but it should last up to more than that, in my opinion.

Again looking at Ashcroft they suggest changing the whole transfer box after 100K miles, hope not to have to do that just yet.....

adamrharding · Jul 14, 2010

Ok an update

Starting the dismantling now, to have a better look, still suspect rear diff., but receptionist thinks VC, but don't know if lead mechanic does.

Fingers crossed they come up with some worn UJ's or similar.

Also should I expect the transfer box to be on its way out at 158k miles? I have read Ashcroft's site on this

Cheers

goonarmy · Jul 14, 2010

a dry prop could have ****ed the diff.You grease em?

adamrharding · Jul 14, 2010

Nah

Not greased them, but different garage did full monty service changing all oils re-greasing etc. back in September.

How often does it need doing?

Cheers

adamrharding · Jul 15, 2010

Anyone know how often re-greasing needs doing?

adamrharding · Jul 15, 2010

An update,

Garage confirm that seized VC and Rear diff are problems, is nearly £900 a good price for for parts and labour?

Cheers

kooky_guy · Jul 15, 2010

adamrharding said:
An update,

Garage confirm that seized VC and Rear diff are problems, is nearly £900 a good price for for parts and labour?

Cheers

Hmm. Well the VC is £295 + VAT at Ashcrofts. Fitting is straightforward for someone who knows what they're doing.

No idea about the diff. Which bit is broken?

Guy

wammers · Jul 15, 2010

adamrharding said:
An update,

Garage confirm that seized VC and Rear diff are problems, is nearly £900 a good price for for parts and labour?

Cheers

VC about £300.00 recon diff around £250.00. to £300.00. On a ramp about two hours for diff, roughly same for VC. So around 4/5 hours labour plus parts. So two thirds of the £900.00 is bits oil etc. Sounds about right to me.

adamrharding · Jul 15, 2010

OK

Parts sourced, garage sourced the rear diff from Ashcrofts but as they are out of stock of the Viscous Coupling I had to source that, found one at Famous Four for £295 + VAT, garage reckon between 3 and 5 hours to fit both, is this reasonable?

cheers

Rear Diff, Viscous Coupling HELP

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