Limited slip diffs

[Burnerman]

Just had a Kia Sorento (06 plate) in for service, repair and MOT.
The rear diff was due an oil change, but there's two recommendations for the lube - one type for conventional diff and one for a LSD.
How would I tell if it has an LSD or not? I called Kia with the reg number but they didn't know either!
Jacking the thing up with the wheels in the air and trying to stop one of them was inconclusive.
John

 

[KingboyD]

This does seem to be a grey area! I've just had a look around & no one on the internet can give a conclusive answer either

Short of stripping the diff to find out my only suggestion is to see if the existing oil in the diff has any unique features such as colour??

Have you given the chassis/reg number to Kia & they still don't know?

Try another dealer maybe

 

[Burnerman]

Many thanks for the reply, KBD
I thought all I had to do was to contact Kia and they would find out for me by their database.......no chance on that one, but I guess the code would be hidden somewhere in the VIN number.
No matter. The oil spec for no LSD was 75/90 semi synthetic hypoid and for the LSD an 80/90 mineral......thats fairly typical.
So....in went the semi synth, on the assumption if that oil was too slippy, it would simply override the clutch but not do any harm mechanically - my logic anyway!
The oil that came out was very black, surprisingly - so thats maybe why its recommended to be changed every 30k. The magnetic plug did have some fuzz on it but no chunks
The owner doesn't mud plug with this thing - its just a caravan towing barge so an LSD would hardly operate anyway.
John

 

[woosey]

if you jack the axle up so the wheels are off the ground, spin one wheel, if the other wheel rotates the opposite way, it's an open diff, if it rotates the same way it's an lsd...

 

[KingboyD]

Many thanks for the reply, KBD

Hey don't mention it

If the oil came out quite black then my assumption would be there are clutches at work inside indicating an LSD, the oil you have used will prob not affect it tho

 

[Burnerman]

Two very sound comments there, gents - and got me thinking!
More investigations over the weekend!
John

 

[Dave54]

You may have seen this John:
http://www.kiaownersclub.co.uk/forum/limited-slip-diff_topic2383.html
It says the additives make the oil grey and gives instructions for refilling.
Apparently it's a geared type of LSD.

 

[Burnerman]

Thanks for that link Dave - interesting reading and it appears that there are other people as confused as me about this!
So - investigations today. Both wheels on the deck, spin one by hand. The other one - if it spins at all - is definitely in the opposite direction so to me that says no LSD.
So - the car, with its new axle oil (75W/90 semi) goes back to its owner as it is.
I'm still wondering why the old oil was so black though!
The front axle oil was clear and golden but I suppose thats natural as the 4WD system is (presumably) rarely used.
Happy days! Many thanks for the interest folks
John

 

[Trazor]

Just for interest, this video explains how a Diff works.

http://www.wimp.com/differentialgear/

The best explanation I have ever seen.

 

[Burnerman]

There's sure been some brilliant engineers among us!
The Ackerman steering principle is another gem.
Rule Britannia
John

 

[Avocet]

I'm not familiar with that model but my wife's X-Trail has an open diff at the back and on the nose of the rear diff is an electronic coupling (so it can be 2 or 4WD). The coupling shares the same oil as the diff gears and is an electrically-actuated multi-plate clutch, which either transfers "some" or "quite a lot" of torque to the rear diff as conditions demand. Is it possible this car has the same setup and that's why the oil is dark?