Before you point me in the direction of the list of codes at the top of the Engine & Transmission section, my codes don't seem to match any of them ... ?

It's a 7.5" - lobro flanges and I'm fairly sure it's a 3.92.

Code written on the crown wheel: 9F 1281 3.92
Code stamped on the crown wheel: 88 GG-4210 AA 3.92
Code cast into the casing: 85 GG 4025 CB
Code cast on the rear cover: 85-GG-4033-BA

Is it LSD or non-LSD?

(Pictures uploaded to my Photo Archive.)

AA = LSD
3.92 = ratio

Take a look at the photograph (in my photo archive), is that a helical gear limited-slip differential?

That's an open gear diff, not an lsd. The cwp ratio is 3.92.

Ian

LSD on the left
Note slightly raised section compared with non LSD and webs go to the edge



[Edited on 19/4/13 by snapper]

Looks like a lsd to me

Cheers
David

Thanks snapper.

So it looks like I've got an LSD crown wheel, but open diff gears?

No my LSD is like that, the vicous lsd diff looks like an open diff, they have the lsd bit in the raised section

Cheers
David

How do I test the diff to be sure?

Rotating the input flange/shaft: both output flanges/shafts turn in the same direction.
Stop one output from turning: the other continues to turn.
Rotating one output shaft: the other turns in the opposite direciton.

What does this tell me?

quote:

---

Originally posted by imagineer
How do I test the diff to be sure?

Rotating the input flange/shaft: both output flanges/shafts turn in the same direction.
Stop one output from turning: the other continues to turn.
Rotating one output shaft: the other turns in the opposite direciton.

What does this tell me?

---

Hi

I am resurrecting a 10 year old Sierra axel bought to put rear discs on a Hood 10 years ago and left in the garden to rot.

The writing on the axel beam says its from a Sierra 2.? the date can only be when it was removed.

Solid discs, Lobro shafts, 7.5" differential case.

The metal tag label has ... 89GG AA 3.91 4A 0M01
that I decoded to ... 89GG = 7.5" case AA = LSD ratio 3.91 4A manufacturing plant ??
Date code 1990 December 1st

From the super7thheaven website info I can tell that this diff is from "3.91 ratio Sierra[DL20](Aug90-) and LSD" probably.

I needed to open the diff as the input shaft was "stuck", and to see how much rust there was inside as I knew water could have gotten in thro' the breather pipe.

The Crown wheel was very rusty at the bottom where the water was sitting....but that's another problem.
(The worst has cleaned of and the diff is free, need to see how clean I can get to make usable)

The INK numbers on the crown gear OL 7792 3.91 090

The numbers stamped on the crown gear 89GG 4210 AA 3.91

SO FAR SO GOOD

My problem the diff does not look like an LSD, it looks like the diff on the right in Snappers post above,
there is no obvious place for the viscous LSD to fit in. (backed up by the drawings in the Haynes manual Sierra V6)

SO ARE THE FORD PART NUMBERS WRONG,
or is there another explanation for the wrong numbers.

AA = LSD everywhere I look.

Anyone seen this before

How many people think they have an LSD but have one of these ???

[Edited on 28/7/13 by CellZapper]

Some one swapped the alloy tag ?
Put some photos up
Jacko

Hi Jacko

I think the tag looks ok, matches the crown gear,
and when I bought it I was just looking for disk brakes, there was no need to con me at the time.

I can't remember how or when I got it, but I think we took it of a Sierra in a cow shed, where the seller kept scrap cars.
(and it was cheap, like me, I wouldn't have paid a premium (cossie price) for it)

I will charge a camera and take some photo's (old fogy without camera phone)

Chris



crown gear part number
left view
right view

[Edited on 28/7/13 by CellZapper]

[Edited on 29/7/13 by CellZapper]

maybe I should have made a new reply for the photo's

Open differential by the looks of it

David

^^ forget part numbers - I don't know why anybody trusts them

ford made lots of tiny changes to the diffs/axles over the years - most of which have little or no impact on what we are going to use them for, but every version had a differenct number, even ones just made in other factory seem to have different numbers.... and then they could have easily been swapped about / re-built at some point in there life


The only way to know what you've got is check it over yourself and it should fit one of the following:

a) 7" or 7.5" crownwheel ? (can be spotted by the style of the diff case - 7" have 2 long through bolts, 7.5" have 4 short bolts in there place)

b) To suit push-in or bolt-on shafts (should be obvious enough , LSD's can't use the push-in shafts)

c) Ratio - 7" will be: 3.92, 3.62, 3.38 or 3.14
7.5" will be: 3.91, 3.64 or 3.36 (also 4.09 and 4.27 from the 8v or 16v scorpios)

d) LSD or not ? (as above with the back off you'll see the 'bulge' inside the crownwheel if it is one - but still best to check it works )


to check the ford LSD off the car:
jam the input flange and try and turn one of the output flanges - if it turns fairly easily (there will be a small resistance and the other output flange will turn the opposite direction) then its either an open diff or its a dead LSD
but if its really stiff/hard to turn then it'll be a working LSD

or don't jam the input shaft and turn one of the output ones, if its a working LSD both output flanges will turn the same way and spin the input flange, else the input wou'nt move much and the other output will turn in the opposite direction


there are a few odd ones (like the 6.5" diff out of some euro 1.3 I think)

all you can be sure of with the car models is:
*all the 4x4's have LSD's
V6's have 3.62 / 3.64, 2.0 one have 3.92 / 3.91

*all the sierra cossie's have LSD's (2wd one have bigger flanges/shafts)
all 3.64 or 3.62

*the granny 24v cossie's had LSD's untill they started fitting traction control on later models (all 7.5" 3.64)

but someone could have swapped these at some point in there life

[Edited on 29/7/2013 by mcerd1]

Hi

I know its not an LSD Diff, not that bothered, LSD and Hood 2b is an oxymoron I think. (I admit I am a bit disappointed )

My concern was the way the Tag and the crown gear agreed AA code and ratio, yet the diff is a non-LSD.

I can't believe that someone would go to the trouble of partially replacing the insides, must have been built like this.

I think the rust damage will shorten the life of this particular diff, if I decide to go with disks on the rear axle and use it.

My problem I should have stored it properly, at least I should have blocked the breather pipe properly.

Thanks for the info and guidance.

Chris

I don't belive that all codes with more than one 'A' in them are LSD's or ever were, I've seen too many that weren't