A few questions about LSDs
A few questions about LSDs
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Discussion

Synchromesh

Original Poster:

2,428 posts

196 months

Tuesday 15th October 2013
quotequote all
Just trying to get my head around the various types of LSDs available on cars, but have a couple of questions.

Firstly, am I right in thinking the 3 types are:
-Viscous
-Clutch-type
-Torsen

Have I missed any out?

Secondly, I've read that the viscous and clutch-type LSDs wear out over time. Typically, what kind of mileage are you likely to see from each of these before they start behaving like an open diff?

ETA: I'm talking about purely mechanical diffs, nothing with any electronic intervention.

Edited by Synchromesh on Tuesday 15th October 20:40

s p a c e m a n

12,127 posts

178 months

Tuesday 15th October 2013
quotequote all
Purple Ohm.



Someone was going to say it, might as well have been me

SpaceGhost

121 posts

157 months

Tuesday 15th October 2013
quotequote all
s p a c e m a n said:
Purple Ohm.



Someone was going to say it, might as well have been me
Last time I saw those it ended up in 72 hours with no sleep...

Who me ?

7,455 posts

242 months

Tuesday 15th October 2013
quotequote all
I thought he was talking about REAL MONEY . £SD

davepoth

29,395 posts

229 months

Tuesday 15th October 2013
quotequote all
"We were somewhere outside of Barstow on the edge of the desert when the drugs began to take hold. I remember saying something like "I feel a bit lightheaded; maybe you should drive..." And suddenly there was a terrible roar all around us and the sky was full of what looked like huge bats, all swooping and screeching and diving around the car, which was going about a hundred miles an hour with the top down to Las Vegas. And a voice was screaming: "Holy Jesus! What are these goddam animals?"

s p a c e m a n

12,127 posts

178 months

Tuesday 15th October 2013
quotequote all
Can welded count?

There's an amount of slip provided by the tyres hehe

Synchromesh

Original Poster:

2,428 posts

196 months

Tuesday 15th October 2013
quotequote all
s p a c e m a n said:
Can welded count?
nono

ging84

9,548 posts

176 months

Tuesday 15th October 2013
quotequote all
there are a lot more than 3 types, there are a few different ways they can functions and different combinations of technologies they can use to achieve this, giving lots of possibilities, for example clutch based you have mention covers a very broad range, but torsen is a specific design.

The most obvious one that you have missed out is the purely software based ones you now get on a lot of modern cars, these have no mechanical parts, and work to balance the torque by selectively breaking wheels, some people claim they don't count as an LSD.

Scuffers

20,887 posts

304 months

Tuesday 15th October 2013
quotequote all
ging84 said:
some people claim they don't count as an LSD.
might just be because they are not.

the clue is in the name, differential.

back to the OP's question, basically, your right there are only three basic types, although tgrre are a shed load if variety within each basic type.

typically these days, most will use gear (torsen etc) as they are cheaper to make and have much longer service life without overhaul.


Toltec

7,179 posts

253 months

Tuesday 15th October 2013
quotequote all
The other type I have come across is the AP Suretrac, uses some odd lozenge shaped chunks of metal inside it.

This chap has some good photos on his page


http://www.mycaterham.com/66828/117416.html


littleredrooster

6,412 posts

226 months

Tuesday 15th October 2013
quotequote all
ging84 said:
...selectively breaking wheels...
Yep - that one's broken....and so is that one...

smile

littleredrooster

6,412 posts

226 months

Tuesday 15th October 2013
quotequote all
Scuffers said:
ging84 said:
some people claim they don't count as an LSD.
might just be because they are not.
...and indeed the OP said they didn't count:

Original Poster said:
I'm talking about purely mechanical diffs, nothing with any electronic intervention.

amusingduck

9,861 posts

166 months

Wednesday 16th October 2013
quotequote all
littleredrooster said:
Yep - that one's broken....and so is that one...

smile
hehe

ian_touring

585 posts

235 months

Wednesday 16th October 2013
quotequote all
Superman.

ManOpener

12,467 posts

199 months

Wednesday 16th October 2013
quotequote all
Toltec said:
The other type I have come across is the AP Suretrac, uses some odd lozenge shaped chunks of metal inside it.

This chap has some good photos on his page


http://www.mycaterham.com/66828/117416.html
Then there's the Wavetrac type, which sounds like a hybrid of this and a conventional Torsen diff.

300bhp/ton

41,030 posts

220 months

Wednesday 16th October 2013
quotequote all
Synchromesh said:
Just trying to get my head around the various types of LSDs available on cars, but have a couple of questions.

Firstly, am I right in thinking the 3 types are:
-Viscous
-Clutch-type
-Torsen

Have I missed any out?

Secondly, I've read that the viscous and clutch-type LSDs wear out over time. Typically, what kind of mileage are you likely to see from each of these before they start behaving like an open diff?

ETA: I'm talking about purely mechanical diffs, nothing with any electronic intervention.

Edited by Synchromesh on Tuesday 15th October 20:40
Op, have a read here: http://en.wikipedia.org/wiki/Limited_slip_differen...

Depending on what you are wanting, you may want to look at lockers too. Something like Detroit locker is locked, but under certain conditions will allow differing wheels speeds.

DaveCWK

2,418 posts

204 months

Wednesday 16th October 2013
quotequote all
I've never understood how a viscous coupling 'wears out' - there are no mechanically touching parts and unless the viscous fluid has leaked out surely it will always work? Granted the fluid viscocity could change over time due to breakdown etc so operating characteristics may change, but it should always keep working.


Mr2Mike

20,143 posts

285 months

Wednesday 16th October 2013
quotequote all
DaveCWK said:
I've never understood how a viscous coupling 'wears out' - there are no mechanically touching parts and unless the viscous fluid has leaked out surely it will always work? Granted the fluid viscocity could change over time due to breakdown etc so operating characteristics may change, but it should always keep working.
The shearing action on the viscous fluid causes it to degrade over time until it's virtually no better than an open diff.