How Do I Tell If I'm On Lsd?

[Guest boggie]

Hi all,

I am off to collect a 3.9:1 LSD from a breakers in a couple of days but as I will be taking their word for it I want an easy way to tell if I am getting the unit I have been looking for. Is there identification on the housing or alternatively is there a way to determine ratio by simply rotating the hubs to see how many propshaft rotations I get? Someone correct me if I am wrong but if I jack up the rear of the car and rotate a wheel on a non-LSD the other wheel will rotate in the oposite direction if it is LSD then the other wheel will rotate in the same direction.

Someone must know what to look for, any helpers?

Cheers,

Boggie

P.S. Anyone know a Ford tech help phoneline I could ring to check?

[Guest Peejay]

Yep you're right about whel rotation the LSD will go the same way and non, the opposite. Ratio can be chaecked by counting, I belive the may be a tag on one of the bolts, but that may tell you wrong if the innards have been swapped

 

Pete

[Guest boggie]

Cheers Pete,

OK so when I check the diff out I will rotate a hub and make sure the other goes the same way but not sure what you mean about the tag on one of the bolts. Do you mean that there is a code or mark on one of the holes on the propshaft mounting flange to differentiate (no pun intended!) between the 3.6:1 and 3.9:1 ratio diffs? As it is fairly unlikely that the diff internals would be changed I may use this method for checking ratio.

Regards,

Boggie

[Guest Simon cooper]

The easiest way, assuming it is from a 4x4 is to look at the shaft fittings. if they are bolted to the diff by 6 torx bolts then it is either from sierra 4x4 or from a granny. if from sierra then it will/should be LSD.

the reverse direction test does not always work due to drag on rusty disc etc.

Simon

[Guest paul mercer]

sort of agree with simon. be careful if the diff is not on the car, but you are told it is off of a 4x4. all sierras with abs had the six bolt hole fixing.

 

also, at the speed that you will be turning the diff the 'reverse' test as it seems to have been named may not work anyway. the way the lsd works is by a number of plates inside the diff all turning at the same time, if one wheel turns faster than the other, the fluid in between the discs and the discs themselves heat up, cause friction, and hence cause a limited slip action. there's no way you'll turn them by hand quick enough to do this. (i'm pretty sure this is correct info)

[Guest boggie]

Well I've got it and it seems to be LSD. It has the 6 bolt fitting, came from a Sierra and if you turn one hub the other turns in the same direction, also it is impossible by hand to hold one hub stationary whilst turning the other. Powerslides here I come!

[Guest too much power??]

Your right on the test, ford lsd's are a bitch to turn each wheel independant to each other, what power are you running in your motor, just out of interest??

[Guest boggie]

160 BHP last time I looked