LSD

[Robert XR4x4]

Hi,

I have a 98 SEiW with a 215bhp XE with (I assume) an XR4x4 rear LSD

I was at rockingham at the weekend for my first track day in the Westy and was suffering from spinning one wheel out of the corners quite a lot, especially when it was damp.

Is it just the LSD is not man enough to cope with that much power or could the LSD be faulty?

Can I upgrade it without spening millions of pounds? Is the cossie rwd diff the same unit?

cheers

Robert

[Darren B]

Hi Robert,

Are you sure it's the back wheel spinning up and not a handling issue?  My V8 runs a LSD and sometimes it feels like it's doing that, but it's down to the set-up (and my driving). Have you had the car set-up properly? It makes a world of difference and in my opinion is worth a look before plowing money into sorting the diff (if it's not working properly).

Darren

Edited to add: Someone will be along with a way of checking whether you actually have a LSD, I'm sure.

[Robert XR4x4]

Hi,

Thanks for your reply.

I am pretty certain as the wheel is still spinning in a straight line out of the corner. It was really noticable as the damp track was drying, as I felt the wheel spinning (it's normally the left wheel regardless of left or right corner) on the damp exit then there was then a dry patch on the track where the wheel stopped spinning and the car just gripped and went.

I have not had any car set up done, no idea if anything was done before I owned it as it is a relitively new purchase.

cheers

Robert

[peterg]

First check you do have an LSD, jack the rear of the car off the ground, turn one wheel in a forward direction and if the other wheel turns the same way then it's an LSD, if not then it's probably an open diff...

it's possible that the diff needs setting up/rebuilding as spinning the left rear on a righthand corner is er, unusual    the lighter loaded wheel (ie the right) should be spinning if anything when turning right  

[pete g]

spining a wheel is quite possible with a lsd.they dont stop wheel spin [only traction control will do that]

a lsd will transmit drive to both wheels.

with a open diff if one wheel spins the other one will lose drive.

it could be your using crap tyres

not sure the best way to test a 4x4 lsd apart from doing a racing start and checking you leave 2 tyre marks and not one      

[peterg]

best way of testing suggested in an old thread is "find an open piece of track/tarmac, at a standstill, turn wheel hard to the right and sidestep the clutch with about 5k of revs on....if you do a complete donut then you have an LSD, if it stops halfway with loads of wheelspin on one side then you do not"    

[wacomuk]

do you have push in drive shafts (Type A diff) or bolt on? (Type B diff (lobro)

if you have push in shafts and the diff is standard its not an LSD

The type B diffs came with VLSD the viscus pack can ware out and the diff becomes open

[Kevin Wood]

There's not much you can do with a worn Sierra LSD apart from change the viscous pack. Not sure how much that would cost or even if you can still get them. There's no adjustment.

There is a procedure to check the LSD:

Diff Checking (FSOC)

Basically, jack up both rear wheels, remove roadwheels and, with the vehicle in gear, use a socket on the hub nut to swing one rear wheel through 1/2 a turn in a period of 1 second. 70 +/- 30 Nm of torque should be required to achieve this.

If not to spec, replace the viscous coupling (probably time to buy a Quaiffe).

Kevin

[Robert XR4x4]

There's not much you can do with a worn Sierra LSD apart from change the viscous pack. Not sure how much that would cost or even if you can still get them. There's no adjustment.

There is a procedure to check the LSD:

Diff Checking (FSOC)

Basically, jack up both rear wheels, remove roadwheels and, with the vehicle in gear, use a socket on the hub nut to swing one rear wheel through 1/2 a turn in a period of 1 second. 70 +/- 30 Nm of torque should be required to achieve this.

If not to spec, replace the viscous coupling (probably time to buy a Quaiffe).

Kevin

Excellent, many thanks for that. I'll check it out at the weekend  

[cast iron]

If you have push in shafts and the diff is standard its not an LSD

I have a type A diff, push fit shafts,running an AP suretrac torque biasing diff. They were standard kit for catering vans and road and race sell them.

From the outside there is no way of telling if its standard or not. You would still need to, as Peter suggested, jack the car up and rotate the reer wheels and see which way the other side rotates

[wacomuk]

If you have push in shafts and the diff is standard its not an LSD

I have a type A diff, push fit shafts,running an AP suretrac torque biasing diff. They were standard kit for catering vans and road and race sell them.

From the outside there is no way of telling if its standard or not. You would still need to, as Peter suggested, jack the car up and rotate the reer wheels and see which way the other side rotates

what i meant to say was if its a standard sierra diff, i wasnt aware that vans had the same diff

how much are the suretrac torque biasing diffs?

i was told by BGH and SPC that the standard Type A sierra diff was an open type

[stu999]

QUOTE

i was told by BGH and SPC that the standard Type A sierra diff was an open type

It is. As standard... The difficulty is identifying whether the diff is standard or not. I think that Cast Iron was trying to point out that it cannot be automatically assumed that if the diff has push-in shafts, it isnt an LSD. Quaife do an LSD to fit push-in's too IIRC

[Kevin Wood]

Not sure now other types of diff would behave when subjected to the diff test, BTW. Other types of diff would probably behave like either an open diff or a welded diff or somewhere in between. If it's known to be a Ford viscous LSD that will tell you what condition it's in though.

Kevin

[Robert XR4x4]

The shafts are bolt on type.

However, with both wheels jacked off the ground, out of gear and handbrake off I can turn either wheel freely and the other wheel stays still!!! It doesn't turn forward, backwards or move at all .... any ideas (other than throwing it away and starting again!)

cheers

Robert

[melt]

Robert,

Noticed from the photo that you have the ali identification plate on you diff.  I have some details that may identify your diff, don't know where I got them from but they may help.

The ratios and their tag numbers (little ali plate on diff case) are here:

85GG 4006 DC --- 3.97

85GG 4006 BC --- 3.62

85GG 4006 AC --- 3.38

85GG 4006 FB --- 3.36

87BG 4006 GB --- 3.14

86GG 4006 AAA --- 3.92 LSD

V87BB 4006 BAA --- 3.62 LSD

V87BG 4006 CAA --- 3.38 LSD

85GG 4006 AAA --- 3.36 LSD

Vin plate codes for Diff ratio

Ratio Code

3.14 M

3.36 A

3.38 U

3.62 V

3.64 3

3.92 D

HTH

Mel