diff locks explained - Page 2

MikeNZ · 26-05-09, 11:25 PM

...probably because of the over-confidence factor engendered by the 'I'm driving a quattro' feeling. As Scotty from Star Trek said: "I cannae change the laws of physics Captain". And neither can a quattro, good as it is. The word 'masking' is the key one - all that is happening is that the aquaplaning is not as apparent - but it is still happening. And when it really does let go, the car is going a lot faster than some lesser vehicle. Someone once said that due to this factor, quattro drivers have much bigger and better smashes than anyone else. Though ironically, the quattro I wrote off was on a nice dry day (diffs unlocked of course). Still gutted.

20vcqdriver · 27-05-09, 11:08 AM

Quote:

Originally Posted by BasilNZ

That fellow msh with his Borat English is correct. You can only ever lock three wheels on a Type 85 quattro (non Torsen). Whichever front wheel loses traction first will spin and all the torque will be directed to that wheel. You cannot totally lock the system because the front differential is always open.

In fact, no road going Audi with quattro drive has ever had a locking front differential.

Ah yes but in order for it to get to that front wheel it has to go through the centre diff which if it is locked means the rears will be getting driven even if the front one has no grip.

msh · 28-05-09, 08:51 AM

I don't think it's problem with mk1 quattro, because it does have lockable center dif. ...unlike later quattro generations with torsen, which means car have awd only in motion but standing car have bigger chance to get stuck than fwd

On enough bad surface, of course. Btw ir remember one man, who believed that diff lock button in he's B4 2.0q locks all wheels - I explained him, what does this button really does

P.S. BasilNZ thanks

MikeNZ · 28-05-09, 04:31 PM

Quote:

Originally Posted by BasilNZ

In fact, no road going Audi with quattro drive has ever had a locking front differential.

...with the honourable exception of the Treser Hunter IIRC.

stoop44rio · 31-05-09, 07:42 PM

i take it the quattro when rallying would have the diffs locked at position 2 unless it was on tarmac? or did the rally cars have a different system.? can the diff locks on a type 85 be engaged/disengaged at road speeds or can this cause damage?

20vcqdriver · 31-05-09, 08:49 PM

The rally cars did not come with a centre diff, they were a solid drive to front and rear (as if centre diff was permanently locked).

Booty · 31-05-09, 09:47 PM

Yes the Rally quatts were a solid drive, which is why they were ' a pig ' to drive ( Malcolm Wilsons words not mine). The early Subaru Legacy that McRae drove was also solidly locked and would not turn unless you really provoked the car by severly upsetting it's balance. I'm not sure what effect having the centre diff locked would have if locked for a long time but I think it's fine for short periods at least.

MikeNZ · 01-06-09, 10:20 AM

This might be helpful...

http://www.kvquattro.com/techdocs/diffLocks.html

Essentially, you could drive around with the centre diff locked all the time, but it serves no purpose at all on dry tarmac. You will find that the drivetrain makes funny noises during tight turns.

That is not to say there are no consequences - as the wheels cannot turn freely in relation to each other the drivetrain will be under greater torsional (twisting) stresses which will definitely shorten the life of drivetrain components if constantly locked, diffs will wear out more quickly etc. Tyres will also wear out more quickly due to being scrubbed against the road surface on turns. Of course, none of this matters on a rally car.

In extremis, something could snap, but the quattro drivetrain is very robust so it is unlikely to happen unless there has been serious abuse.

I wouldn't treat my car in that way though.

As I said, there are no stated speed restrictions for employing diff locks for mechanical reasons, (though for handling reasons high speed use of the rear lock is definitely not recommended), but as the instruction manual says, you are using them when it is slippery, so you should not be driving fast anyway. It does state that the rear lock should only be used in extremely slippery conditions to start the car off, and to turn it off when moving. The later cars disengage the lock automatically at 15mph for this reason.

31-05-09, 08:49 PM	#16
20vcqdriver 4 ring whore! Classic Audi Club Member Join Date: Dec 2007 Location: Wirral Posts: 3,910	The rally cars did not come with a centre diff, they were a solid drive to front and rear (as if centre diff was permanently locked). __________________ Coupe quattro 1986:-~450bhp + loooong list of mods! Audi A7 Bi-TDI SLine Black edition 2015 mapped to produce 600lb/ft torque! Audi S4 4.2 V8 cabriolet 2004:-

31-05-09, 09:47 PM	#17
Booty Moderator Classic Audi Club Member Join Date: Sep 2007 Location: Deepest darkest Shropshire Posts: 5,077	Yes the Rally quatts were a solid drive, which is why they were ' a pig ' to drive ( Malcolm Wilsons words not mine). The early Subaru Legacy that McRae drove was also solidly locked and would not turn unless you really provoked the car by severly upsetting it's balance. I'm not sure what effect having the centre diff locked would have if locked for a long time but I think it's fine for short periods at least. __________________ 1987 Audi Coupe quattro - Clarion Tribute Car 2012 Audi A6 Allroad 2004 Mercedes SLK 350 2017 Mercedes GLA 220

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
lockable front diff?/Torsen front diff?	Gaz	Transmission	10	16-01-10 01:54 AM
80 coupe locks for a saloon?	silverStoned	Bodywork, glass & exterior fitments	7	06-01-10 09:52 AM
ABS and Diff locks	andy	Transmission	8	11-11-09 10:10 PM
WR diff locks	andy	Transmission	6	24-08-09 11:53 AM
80 doors locks	maynd	Bodywork, glass & exterior fitments	9	28-01-09 11:26 PM

26-05-09, 11:25 PM	#11
MikeNZ Grown up member Join Date: Jul 2008 Posts: 246	...probably because of the over-confidence factor engendered by the 'I'm driving a quattro' feeling. As Scotty from Star Trek said: "I cannae change the laws of physics Captain". And neither can a quattro, good as it is. The word 'masking' is the key one - all that is happening is that the aquaplaning is not as apparent - but it is still happening. And when it really does let go, the car is going a lot faster than some lesser vehicle. Someone once said that due to this factor, quattro drivers have much bigger and better smashes than anyone else. Though ironically, the quattro I wrote off was on a nice dry day (diffs unlocked of course). Still gutted.

28-05-09, 08:51 AM	#13
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	I don't think it's problem with mk1 quattro, because it does have lockable center dif. ...unlike later quattro generations with torsen, which means car have awd only in motion but standing car have bigger chance to get stuck than fwd On enough bad surface, of course. Btw ir remember one man, who believed that diff lock button in he's B4 2.0q locks all wheels - I explained him, what does this button really does P.S. BasilNZ thanks

31-05-09, 07:42 PM	#15
stoop44rio Grown up member Classic Audi Club Member Join Date: Aug 2008 Location: antrim, ireland Posts: 504	i take it the quattro when rallying would have the diffs locked at position 2 unless it was on tarmac? or did the rally cars have a different system.? can the diff locks on a type 85 be engaged/disengaged at road speeds or can this cause damage?

01-06-09, 10:20 AM	#18
MikeNZ Grown up member Join Date: Jul 2008 Posts: 246	This might be helpful... http://www.kvquattro.com/techdocs/diffLocks.html Essentially, you could drive around with the centre diff locked all the time, but it serves no purpose at all on dry tarmac. You will find that the drivetrain makes funny noises during tight turns. That is not to say there are no consequences - as the wheels cannot turn freely in relation to each other the drivetrain will be under greater torsional (twisting) stresses which will definitely shorten the life of drivetrain components if constantly locked, diffs will wear out more quickly etc. Tyres will also wear out more quickly due to being scrubbed against the road surface on turns. Of course, none of this matters on a rally car. In extremis, something could snap, but the quattro drivetrain is very robust so it is unlikely to happen unless there has been serious abuse. I wouldn't treat my car in that way though. As I said, there are no stated speed restrictions for employing diff locks for mechanical reasons, (though for handling reasons high speed use of the rear lock is definitely not recommended), but as the instruction manual says, you are using them when it is slippery, so you should not be driving fast anyway. It does state that the rear lock should only be used in extremely slippery conditions to start the car off, and to turn it off when moving. The later cars disengage the lock automatically at 15mph for this reason.