Thread: Whats the difference between a locking center diff and Viscous Coupling

The centre diff in the LT230 is an open diff which has a locking mechanism to physically lock the front and rear output shafts.

A viscous coupling is a device that contains thick silicone fluid between the input and output which allows the front output to drive at a different speed to the rear. When the coupling fails it usually seizes making the coupling the same as the centre diff in the locked position and other drive trail failures will result, usually one of the front CV.

The only main benefit of the viscous coupling is that it doesnt require any input from the driver to work. Effectively 4WD for dummies and why it was fitted to the RRc and P38 automatic.

So the viscous coupling works to lock the center differential automatically?

Yes, and as has been said, 's Centre-Diff locking for the bone lazy, stupid, or too arrogant to lean over and move a lever.

Supposed to have some advantages in sand, but the 'silicon' degrades with use. - Anything from 80k to 250K. Uneven tyre pressures F/R wil shorten its live again.

You must never mix new-ish with older tyres. Or differant brands.


VC failure is usually noticed by chirping of the front tyres when turning, and turning wider than normal in wet weather... at which point you remove the front prop shaft, and enjoy the marginally better fuel use of a RWD car.

Or buy a good LT230 if you're into serious or regular 4WD fun.

Disclaimer:- I hate, loathe and detest the concept and execution of the RRC viscous coupling ...

'95 Vogue SE with working EAS...and 2WD.

Thanks Guys,

Is there anything like a 2wd conversion kit for range rovers that allows for driving in 2wd and then locking into 4wd?

I know they make them for 80-100 series land cruisers but I've never seen anything for land/range rovers/

Interesting comments above. I bought an 89 Rangie auto which just happened to have a viscous coupling. It may not be everyones experience but my vehicle travelled around 650.00 kms trouble free from the coupling and transfer case. It still worked perfectly when I sold it. The vehicle was used as a 4wd and driven on as hard a tracks as a road legal vehicle could travel on.
Having had other Rangies with the lt230 and lt95 I can say as a daily driver the viscous transfer is nicer to have being quieter and smoother.

it has nothing to do with being lazy or too stupid to move a lever.

Ian

Originally Posted by Lotz-A-Landies

The only main benefit of the viscous coupling is that it doesnt require any input from the driver to work. .

Another benefit is that there is much less backlash in the driveline of a viscous diff equipped Range Rover, which makes them smoother to drive, particularly with a manual transmission.

Having owned my 92 for 13 years , I feel I am qualified to comment.
people who have trouble with their BW transfer maybe rightly hate them ( especially if they have been stuck in the boonies) , and ignore the several problems with LT230s like the frequent happening of disintegrating Thrust washers in the centre diff and elongation of the idler shaft mount holes.

My BW has now done 222KKs , and I had to replace the output shaft at about 180KK. I would recommend anyone who owns one to check it before going to the boonies if they have 160KK or more. ( A new one is about $200 to buy in UK and 4 hours to fit in situ)

My VC still seems excellent as I check it whenever I take a front wheel off. To me the Rear output shaft is really their only weakness. And I am not gentle on mine having towed my camper up the Northern OTT , the GRR and just about every other iconic track in OZ.

I guess the biggest difference is that if you strip an output shaft or CV or axle you are stuck, whereas with an LT230 you can disconnect the offending axle and get home.


IMHO, there is very little difference of ability in various terrains between a locked case and a VC. I have climbed a creek exit in the Northern OTT with a campertrailer which 4WDDrive Action twin locked Toyos had great difficulty with. Similarly the Mount Airlie track in the old days when it was hard.

Last year I bought a 335KK BW , in which the seller thought the chain was broken. It wasn't . It was the output shaft. Now to me 335 KK is a VERY good run, and a high proportion of LT230 will have trouble by that time.

PS I do have another 10years experience with LT95

Regards Philip A

One more questions?

Why cant you just removed the offending driveshaft in a RR with the VC??

Thanks Heaps!