Sierra Differential

Fed up with reading dodgy information on all those forum sites?

Have you ever needed Ford Sierra Diff Ratios?
Or needed Sierra Part Numbers?
Find Exploded diagrams and FINIS part numbers.
This is the most accurate Sierra Differential information available on the web.

Locost 7: Ford Sierra 86 Diff Part Numbers
Ford Sierra 86 Diff Microfiché

Locost 7: Ford Sierra 92 Diff Part Numbers
Ford Sierra 07/92 Diff Microfiché

Ford Scorpio Diff Ratios, link to make and model,
complete with Scorpio Part Numbers.

All diagrams are listed with FINIS information making this the most accurate Scorpio Differential information available.
Locost 7: Ford Scorpio 95 Diff Microfiche
Ford Scorpio 95 Diff Microfiché

Ford Granada Diff Ratios, Granada Part Numbers. and Granada Diff Overhaul and Rebuild information
Accurate Granada Differential information direct from Ford. 


Locost 7: Ford Granada 92 Diff Microfiche
Ford Granada 92 Diff Microfiché

Engine CodeEngine
TL131.8 8v
TL161.6 8v
TL181.8 8v
TL202.0 8v
TL20H2.0 8v HC
TL20INJ2.0i 8v
CL202.0
VW191.9TDi
DL202.0i 8v
DH202.0i 16v
DH232.3i 16v
LL23INJ2.3i
PD232.3D
PD25T2.5TD
VM252.5TD
VV282.8 v6 12v
TV232.3 v6 12v
TV242.4 v6 12v
TV282.8 v6 12v
TV28INJ2.8i v6 12v
TV292.9 v6 12v
TV29INJ2.9i v6 12v
CP292.9 v6 24v
CP29INJ2.9i v6 24v
EV303.0 v6 12v

CAD drawing of Ford Sierra Diff, 7″ push in shaft type (Tripod).
Locost Sierra Tripod Diff Push In shafts
Despite its’ age, the Ford Sierra Diff still dominates as the No. 1 choice of diff for kit car builders. It’s been well documented that they can cope with 300bhp without too much hassle and even very high mileage units show very little signs of wear. Various differentials were looked at for this design. For instance the modern Jaguars have strong differentials but their final drive ratios are far too low, the same also applies to many Nissan and BMW diffs.
Sierra Rear CAD Diff Assembly
http://www.youtube.com/watch?v=llLvCEz4AhE
The other advantage of these differentials is that they can still be found in reasonable supply on auction websites. The price is slowly increasing and maybe one day soon the BMW unit will take over, but for now it is here to stay.
There are a vast array of drive ratios, some more common than others. Casings are available in 7″ or 7.5″ formats with push in or bolt on shaft fitments. The push in versions are also available with a different number of splines. Some are available with LSD others not. The choice is bewildering.

Identifying your Ford Sierra differential.

If the donor car is available you can read the VIN plate, for the “Final Drive Code” or “AXLE”. The final drive ratio is describe by a letter.

A=3.36(crown wheel 44 teeth, pinion 13 teeth, 7.5″ diff casing)B=3.77D=3.92(crown wheel 51 teeth,pinion 13 teeth, 7″ diff casing )
F=3.842J=4.056K=3.31
M=3.14(crown wheel 47 teeth, pinion 15 teeth, 7″/7.5″ diff casing)N=4.29P=3.58
U=3.62<(7″ diff casing)V=3.33(crown wheel 47 teeth, pinion 13 teeth, 7″ diff casing)Z=3.59
2=4.273=3.62 / 3.64?4=3.82
5=3.266=3.128=3.56
9=3.91(7.5″ diff casing)  

If the VIN plate is not visible, there maybe a small aluminium tag attached to the top left hand side of the rear cover. There are a vast number of codes and it maybe that a visit to your friendly Ford dealer is in order. There are many web sites and magazine articles, quoting codes and ways of deciphering the codes and often the information is conflicting or simply incomplete. The only real way to identify a diff is to physically test it. For instance, if you turn the front flange and both drive flanges rotate in the same direction, it’s an LSD.

As a rough guide…..

locost Sierra Diff Identification Tag
Identification on Tag.

  1. Casing style
  2. Axle Ratio E.g. 3.36:1
  3. Assembly Plant
  4. Build Date
    • 4 = Build Year (1984)
    • L = Build Month
      • A = Jan, B = Feb, C = Mar, D = Apr, E = May, F = Jun, G = Jul, H = Aug, J = Sep, K = Oct, L = Nov. M = Dec
    • 11 = Build Day (11th)

On some Sierra diff ID plates the numbers will be in a different format. There will be some numbers / letters (look at the top row)
EG. 85GG 4006 DC
The first set (85GG) is the case type (7″ or 7.5″) and the easiest way to identify a 7″ and 7.5″ is to look at the top mounting. The 7″ (left) has one long bolt/nut and the 7.5″ (right) has 2 bolts.
image: 7 and 7.5 inch Sierra Diff mounts

NB. The unit on the left is a Tripod unit with push in shafts and the right hand unit is the more desirable Lobro unit with external bolt flanges for the drive shafts.
In this view you can clearly see the size difference (7.5″ on left):
image: Sierra Differential Sizes 7.5inch on Left 7inch on right
NB. The internals of the 7″ are almost identical to the 7.5″ (apart from the reduction gear ratios), so there are no differences in strength.
The other non−numeric code (middle or end), in this code its ‘DC’ which is an ‘OPEN’ type diff (NON-LSD). Generally, any diff with 2 or more “A” in the middle code will be an LSD e.g. “AA” or “ABA”. This doesn’t mean that if it hasn’t, it’s not an LSD, it’s just easy to remember. There are several exceptions to this rule.
Some codes are in the format 85BB 362 AA.
In this case, the first 4 digits (85BB) are still the casing code and the AA is the diff style (In this case LSD). The middle 3 digits represent the ratio (in this case 3.62 :1)
image: Sierra Differential Code Plate
Another way to identify what ratio you have is to undo the T50 Torx bolts securing the rear cover and inspect the writing and stamps on the internal gearing.
If you are lucky there will be some handwriting to the large Crown gear. This is easily rubbed off.
The 7″ differential below is from a Escort Cosworth 4×4.
Escort Cosworth Diff Internal Markings
In this case the yellow writing states ‘2E 603 362’. The ‘362’ indicates this is a 3.62:1.
If this writing has been lost then also stamped into this Crown gear is the Ford part number.
The number reads ‘Ford 90BG-4210AA 3,62’.
By counting teeth of the Crown and Pinion gears you can calculate the ratio.
47/13 ≈ 3.6154’ (3.62:1)
Escort Cosworth Diff Number Stamp

Sierra Diff
EngineModelTransmissionRatioNumber of Teeth
Sedan AxleEstate AxleManAutoRing GearPinion
1.6 OHC 2V6.5″
7″
7″XSedan 3.62
Estate 3.92
47
47
13
12
1.8 OHC 2V6.5″
7″
7″XXSedan 3.62(1)
Estate 3.62(1)
Sedan 3.92(2)
Sedan 3.38(3)
47
47
47
44
13
13
12
13
2.0 OHC 2V7″7″XX3.62
3.38(4)
47
44
13
13
2.0 OHC EFI7″7″XXX3.92
3.62
3.62(5)
47
47
47
12
13
13
2.0 OHC EFI MC7″7″XX3.624713
2.8 V6 HC FI 4×47″7″XX3.624713
2.8 V6 HC EFI7.5″7.5″XX3.36(5)
3.36(5)
47
47
14
15
2.8 V6 HC EFI 4×47″7″X3.62(5)4713
2.3 Diesel7″7″X3.384413

(1)Not for 5 speed right hand drive sedan (& LHD Italy + Spain)

(2)Only for 5 speed right hand drive sedan
(3)Only for France
(4)Not for Sweden
(5)Only for Sweden
The 7.5″ rear Granada / Scorpio differential has a different shaped housing.
Granada Scorpio 7.5 inch rear diff casing(FINIS CODE 6141389)
The following table is a collation of what I have found :
(unfortunately, I cannot verify this data)

85GG 4006 FB,
8500 4006 FB

Ford Sierra Differential Ratios
RatioVehicleShaftDiffTeethFINISPart No.
3.14Sierra[TL16](−Mar83)(D),
Sierra[TL16](−Apr83)(UK),
Sierra[TV23,PD23],
Sierra[TV28INJ−AUTO],
Sierra[TL20H](non−ABS),
Sierra[DL20H](non−ABS),
Sierra[PD23](−Jan90)(non−ABS)
TripodNon−LSD 610762483BG 4006 KC
3.14Sierra[TV28INJ](−Jan90)LobroNon−LSD 164489985GG 4006 GB
3.14Sierra[DL20](ABS),
Sierra[PD23](ABS)(−Jan90),
Granada[DL20](Feb92−)
LobroNon−LSD 615210087BG 4006 BA
3.14Granada[DL20](Feb92−)LobroLSD 619318188GG 4006 AEA
3.14Sierra[TL16,TV23,PD23]TripodLSD 1619200V83BG 4006 AA
3.14SierraLobroLSD 1648395V87BG 4006 DAA
3.36Sierra[TV28INJ](5Spd−Type9)TripodNon−LSD 613119583BG 4006 BA
3.36Sierra[TV29](Jan90−May91)LobroLSD 614222285GG 4006 AAA
8500 4006 AAA
3.36Sierra[LL23INJ](XR4)(USA/CDN),
Sierra[TV28](−Jan90),
Sierra[TV29](−May91)
LobroNon−LSD 6124451
3.36Sierra[TV29](2WD)(May90−),
Granada[TV29](2WD)(Feb92−),
Granada[PD25T](Feb92−)
LobroLSD 666390591GG 4006 AAA
3.36Sierra[TV29](May90−),
Granada[TV29](2WD)(Feb92−),
Granada[PD25T](Feb92−)
LobroNon−LSD 666390891GG 4006 FA
3.36Granada[CP29]LobroLSD 683123793GG 4006 AAA
3.36Granada[VM25](Aug93−),
Scorpio[VM25](Oct94−Jan96)
LobroNon−LSD 680339994GG 4006 AA
3.36Scorpio[VM25](Jan96−)LobroLSD 102611696GG 4006 BDA
3.36Scorpio[VM25](Jan96−Sep96)LobroNon-LSD 101563096GG 4006 FA
3.36Scorpio[VM25](Sep96−)LobroNon-LSD 103542497GG 4006 AA
3.38Sierra[HL18](Jan91−),
Sierra[D18T](Jan90−),
Sierra[TL16,TL18,TL20,TL20H,TV20,TV23,PD23]
TripodNon−LSD 610762583BG 4006 LC
3.38Sierra[TL18,TL20,PD23]
Sierra[HL18](Aug89−),
LobroNon−LSD 163000485GG 4006 AC,
8500 4006 AC
3.38Sierra[TL16,TL20,TV]TripodLSD? 1619201V83BG 4006 BA
3.38SierraLobroLSD 1648394V87BG 4006 CAA
3.62Sierra[TL16,TL18](Jun85−),TripodNon−LSD 610762383BG 4006 CC
3.62Sierra[TL16,TL18](Jun85−),TripodNon−LSD23615771583BG 4006 CD
3.62Sierra[TL18](Man)(Jun85−),TripodNon−LSD26615771583BG 4006 CD
3.62Sierra[TL20H,TV,TL18,HL18],
Sierra[TL20INJ](GL,GHIA,2.0iS],
Sierra[TL20,DL20](−Jan90),
Sierra[TL20,DL20,D18T](Jan90−)
TripodNon−LSD 610762683BG 4006 MC
3.62Sierra[TL16,TL18](Jun85−),
Sierra[TL16]
TripodNon−LSD26610762683BG 4006 MC
3.62Sierra[TL18](Man)TripodNon−LSD28610762683BG 4006 MC
3.62Sierra[TV28INJ](XR4)TripodNon−LSD 612429583BG 4006 RC
3.62Sierra[TL16,TL18,TL20,DL20]LobroNon−LSD 614656085GG 4006 BC,
8500 4006 BC
3.62Sierra(TV28INJ)TripodLSD 1619202V83BG 4006 CA
3.62Sierra[TV28INJ,DL20,TV29],
Sierra[CH20](Feb90−),
Granada[CP29](4wd)(Feb92−)
LobroLSD 1627946V85BB 4006 AA
3.62Sierra[DL20](Jan90−),
Sierra[D18T]
LobroLSD 1648393V87BG 4006 BAA
3.64Granada(85−92)LobroLSD  85GG 4006 ACA
3.64Sierra[LL23INJ](XR4)(USA,CDN)LobroNon−LSD 613751085GG 4006 HB
3.64Sierra(Cosworth)LobroLSD  86BB 4006 AAA
3.64Granada(2WD)(Feb92−)LobroLSD 666390791GG 4006 ACA
3.64Scorpio(Cosworth)LobroLSD  91GG 4006 ADA
3.64ScorpioLobroLSD  95GG 4006 ACA
3.64Granada(2WD)(Feb92−)LobroNon−LSD 666391091GG 4006 HA
3.64Scorpio[CP29](Oct94−Jan96),
Scorpio[TV29](Oct94−Jan96)
LobroNon−LSD 703588895GG 4006 JA
3.64Scorpio[TV29](Jan96−Aug96)LobroLSD 102611496GG 4006 BCA
3.64Scorpio[CP29](Jan96−),
Scorpio[TV29](Jan96−Aug96)
LobroNon−LSD 101563496GG 4006 EA
3.77Sierra[TL13]TripodNon−LSD 609950983BG 4006 AC
3.77Sierra[TL13]TripodNon−LSD 163752383BG 4006 AD
3.91Sierra[DL20](Aug90−)LobroLSD 649006589GG 4006 AA
3.91Sierra[DL20](Jan90−May91)LobroLSD 649006689GG 4006 AAA
3.91Sierra[DL20](May91−),
Granada(Feb92−)
LobroLSD 666390691GG 4006 ABA
3.91Sierra[DL20](May91−),
Granada(Feb92−)
LobroNon−LSD 666390991GG 4006 GA
3.91Scorpio[DH23](May96−)LobroNon−LSD 101752396GG 4006 BA
3.92Sierra[TL16](−Oct84)TripodNon−LSD 609951483BG 4006 JC
3.92Sierra[TL16](Oct84−),
Sierra[TL20INJ](2.0iS),
Sierra[TL16,HL18,TL20]
TripodNon−LSD 162716483BG 4006 JD
3.92Sierra[TL16,TL18,HL18,TL20INJ],
Granada(Feb92−)
LobroNon−LSD 614656185GG 4006 DC,
8500 4006 DC
3.92Sierra[DL20](Jan90−),
Granada(Feb92−)
LobroLSD 617146586GG 4006 AAA,
8600 4006 AAA
3.92Sierra[DL20](−Oct90)TripodNon−LSD 649006489BG 4006 AA
3.92Sierra[DL20](Oct90−May91)TripodLSD 649006489BG 4006 AA
3.92Sierra[DL20](May91−)TripodLSD 666390491BG 4006 AA
3.92Sierra[TL16]TripodLSD 1619204V83BG 4006 EA
3.92Sierra[TL16],
Sierra[TL20INJ](2.0iS)
TripodLSD 1630675V83BG 4006 EB
4.09Scorpio[DL20](Jun95−Jan96)LobroLSD 101374795GG 4006 AAA
 Scorpio[DL20](Oct94−Jan96)LobroNon−LSD 703588695GG 4006 AA
4.09Scorpio[DL20](Jan96−)LobroLSD 101562696GG 4006 BAA
4.09Scorpio[DL20](Jan96−)LobroNon−LSD 101562196GG 4006 CA
4.27Scorpio[DH20](Oct94-Jan96)LobroNon−LSD 709152195GG 4006 LA
4.27Scorpio[DH20](Jan96−May96)LobroNon−LSD 101562796GG 4006 DA

The following cars were fitted with LSD’s but it also always important to double check.

  • All 4×4 Sierra’s and Granada’s (2.8/9 and 2.0DOHC and Cosworth)
  • Most but not all 24v Cosworth Granada/Scorpio (up to approx 1994 are LSD, after that they are ‘open’ type because the Scorpio 24v had traction control instead)
  • All RWD Cosworth Sierra (3dr, Sapphire, RS500)

Diff Mountings

As mentioned above there are two sizes of diff casing (7″ and 7.5″).
The 7.5″ is available with two different rear covers (top mount and ‘Koala’ rear mount). Both covers are interchangeable. The ‘Koala’ rear mount diffs are from the late model ‘face-lift’ Granada’s, known as Scorpio or Ultima.
The top mount diffs have 4x13mm bolts (early) or 4x15mm (later).
image: Sierra top mounting rear coverimage: Rear mount Granada diff
The Sierra diff has 2 types of drive-shafts: Lobro (Bolt-on – left picture) and Tripod (Splined – push in – right picture).
Diffs with Tripod type shafts are designed to be used with Drum Brake equipped hubs, However, it is possible with the use of adaptor plates or hybrid shaft / hub combos, to use disc brakes. Bolt−On units are favoured as ultimately they are stronger, but for less extreme applications the Lobro units are fine.
image: Sierra Lobro Diffimage: Sierra Tripod Diff

Final Drive Ratios

The gear ratios of the MT75-4×4 gearbox are :

  • 1st Gear – 3.89
  • 2nd Gear – 2.08
  • 3rd Gear – 1.34
  • 4th Gear – 1
  • 5th Gear – 0.82

I’ve found a very useful gear calculator here :
image: MsExcel Gear ratio calculatorMs Excel Gear Ratio Calculator
The plan for this project is to use 265x30x19 tyres, coupled to a 3.62 diff. Ideally, the diff ratio should be closer to 4.27:1 but unfortunately this front diff ratio is not available. With this combination the theoretical top speed would be close to 155mph. Having been in a Super 7 at 120mph, I know 150mph would be more dumb than challenging.
image: Final Drive Ratio

The Sierra Diff 4×4 route

With the aim being to go 4wd, the choice drops drastically. The Sierra front diff comes in 2 ratios, 3.62:1 & 3.92:1 (now very rare).
The target donors would be :

  • 2.0lt DOHC 4×4 Sierra (1982-1993) – 3.92:1 (rare!)
  • 2.9V6 4×4 Sierra (xr4x4i) -3.62:1
  • Cosworth Sierra 4×4 -3.62:1
  • 1.8 Turbo Diesel Sierra (with ABS) -3.62:1
  • Cosworth Escort 4×4 (1992-1996) -3.62:1
  • Granada Scorpio (1985-1991) -3.62:1
  • Granada 4×4 -3.62:1

If you want LSD the choice drops even further – see above list
Going the 4×4 route with the MT75 gearbox and Sierra diffs, there will be a permanent 34% / 66% split on front / rear power. Therefore, most of the power is going to the rear, hence why only the rear differential was fitted with Limited Slip.