What Dif Is This?

[Guest Logix_00]

While working on the back brum break, I realised that as I don't have a lot of history about my car I don't actually know what dif I've got at the back. The donor engine so assuming running gear as well is from and old Y reg Ford Sierra. I've attached the photo of what it looks like (dunno if that will help) and the number I think that was embossed on it is "83BG4033-AE" Thanks

[Guest Spencer Griffiths]

Copied from the Locost Builders site, diff ratios:

 

Diff Codes ( Ford Sierra Diff codes, Differential Codes, Diff Numbers, Sierra Diff )

 

Ford axle codes

A=3.36 B=3.77 D=3.92 F=3.842 J=4.056 K=3.31 M=3.14 N=4.29 P=3.58 J=3.62 V=3.33 Z=3.59 2=4.27 3=3.62 4=3.82 5=3.26 6=3.12 8=3.56

 

3,14 CW47-Pin15

3,38 CW44-Pin13

3,62 CW47-Pin13

3,92 CW51-Pin13

3,77 CW49-Pin13 6.5 inch diff

 

3,38 fitted to 1,6 OHC ECO 5 speed

3,38 fitted to 2,0 OHC HC

3,38 fitted to 2.3 v6 ESTATE

3,14 fitted to 1,6 OHC ECO 4 speed

3,14 fitted to 2.3 v6 SALOON

3.14 fitted to 2.3 Diesel

 

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 V

3.62 U

3.64 3

3.92 D

 

Give it a good clean with some gunk and a wire brush then spary with Halfords Hi temp aluminium spray paint, it will look like new, see my build photos.

 

Cheers

 

Spencer

[Snapperpaul]

Jack up one wheel mark top or bottom sidewalk with chalk inside of tyre

Mark prop with chalk,

Rotate wheel one complete turn, count prop rotations.

You may need to be a bit creative with the prop shaft markings and marking the prop bolts will give you 1/4 rotation marks.

It is most likely you have a 3.6, if you have a 3.38 the bike engined boys and the V8's like them 3.14 is very rear

That said I had a 3.38 originally.

[Bob Tucker]

Rotate wheel one complete turn

If one wheel is static, you need to turn the raised one two turns.

Most common ratios are 3.62 & 3.92.

Use the well tried scientific formula "Just over 3 & 1/2", or "Just under 4" LOL

If its neither of these, a bit more accuracy may be needed

HTH Bob

[Longboarder]

The number you need to identify it is on a fragile ally tag held by one of the 10 rear plate bolts, usually the one at 11o'clock. You will be lucky if it is still there and readable. The numbers on the castings are useless. If all else fails the ratio is written on the rim of the crown wheel but its a job getting the back plate off while the diff is in the car. And messy.

 

Nigel

[zygoteer]

Copied from the Locost Builders site, diff ratios:

 

Diff Codes ( Ford Sierra Diff codes, Differential Codes, Diff Numbers, Sierra Diff )

 

Ford axle codes

A=3.36 B=3.77 D=3.92 F=3.842 J=4.056 K=3.31 M=3.14 N=4.29 P=3.58 J=3.62 V=3.33 Z=3.59 2=4.27 3=3.62 4=3.82 5=3.26 6=3.12 8=3.56

 

3,14 CW47-Pin15

3,38 CW44-Pin13

3,62 CW47-Pin13

3,92 CW51-Pin13

3,77 CW49-Pin13 6.5 inch diff

 

3,38 fitted to 1,6 OHC ECO 5 speed

3,38 fitted to 2,0 OHC HC

3,38 fitted to 2.3 v6 ESTATE

3,14 fitted to 1,6 OHC ECO 4 speed

3,14 fitted to 2.3 v6 SALOON

3.14 fitted to 2.3 Diesel

 

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 V

3.62 U

3.64 3

3.92 D

 

Give it a good clean with some gunk and a wire brush then spary with Halfords Hi temp aluminium spray paint, it will look like new, see my build photos.

 

Cheers

 

Spencer

 

Hi,

 

I too have been gathering diff data, but the "J=4.056" and the "85GG 4006 DC --- 3.97" ratios you quote must be mistyped/misquoted, as surely there is no practical combination of Pinion/Crownwheel teeth to achieve such a ratio ?

 

Tony

[zygoteer]

Hi,

 

I too have been gathering diff data, but the "J=4.056" and the "85GG 4006 DC --- 3.97" ratios you quote must be mistyped/misquoted, as surely there is no practical combination of Pinion/Crownwheel teeth to achieve such a ratio ?

 

Tony

 

 

OK, the attached image shows the data I have been able to reasonably verify, so far.

... from this I have the "85GG 4006 DC" down as a ratio of 3.92, so I suspect a typo crept into that post.

 

 

The original data sources have come from a variety of places, about 50% internet (9 known sites), 25% direct experience, 25% Ford manuals.

The only thing I haven't yet fully sorted out is all the different 6.5", or 7", or 7.5" sizes, but working on this.

 

The diffs I have been unable to reconcile are :-

VIN Axle code "5" often quoted as 3.26

VIN Axle code "F" often quoted as 3.84

VIN Axle code "J" often quoted as 4.056

VIN Axle code "N" often quoted as 4.29

These ratios don't really work out correctly with "viable" crownwheel / pinion teeth combinations.

 

As a generalised rule manufacturers don't seem to like the sum of the teeth (CW + P) to exceed 65 (expensive machining time I would guess), and the product (CW x P) to be only rarely greater than about 650 ... although there are inevitably odd exceptions.

This is a tradeoff as a large number of teeth means that the power is spread over a bigger contact area between the pinion and crownwheel, which would give extra strength and quieter running, but the teeth themselves are then also thinner for a given diff size which can limit power capability.

 

If anyone has some more solid data, then please advise.

 

Tony