Which Diff

[AMSQ3D]

How do I know if my differential ia 1600 or 2000, are there any numbers on the casing. The car is a 1600 Vitesse, but not sure if the diff has been changed - Thanks

[Clive]

on the underneath (spring is on top!) on the nose there are some numbers stamped .HB vitesse 1600, 4.11.  FD/HC/KD/FH 3.89 (vitesse 2000 and others) FM 3.63, KC 3.27.
FC/GA also weaker 4.11, GE stronger 4.11. All info from canleys catalogue if anybody spots any errors! :P

The HB diff has a squarish input flange with 5/16" boltrs (1/2 spanner), and 3/8 (9/16 spanner) bolts on the output flanges. The stronger diffs all have round input flanges with the larger bolts. Check out the canleys site for more info.

Cheers
Clive

[heraldcoupe]

[quote by=cliftyhanger link=Blah.pl?b=hervit,m=1164560601,s=1 date=1164561791]
The HB diff has a squarish input flange with 5/16" boltrs (1/2 spanner), and 3/8 (9/16 spanner) bolts on the output flanges. The stronger diffs all have round input flanges with the larger bolts. [/quote]

Not so. The post 1967 Heralds and most Mk3 Spitfires have a 4.11 diff with large shafts and small (square) flanges at input and outputs. Swapping the output shafts for a pair from a late Spitfire or 2L car will give an identical appearance to the original 1600 diff, albeit with large shafts.
Cheers,
Bill.

[JohnD]

I presume you're more intersted in the ratio of your diff than where it came from?

Easy to tell:
On the bench.
Mark the input flange so you can tell how many times it has rotated.
Typpex on the flange and the casing is good.
Mark an output flange as well.
Turn BOTH output flanges at the same time, for one complete rotation.
Note how many times the input flange rotates.

On the car.
On flat ground, take off the gearbox cover, so you can see the proshaft.
Mark it as above.
Mark a rear tyre, at the point nearest the ground.
Now push the car for one complete wheel roatation, noting the number of propshaft rotations.
A helper in the car is useful.  Of course, if you can persuade your helper to push while you count .......

Just more than 4 = 4.11
Just less than 4 =  3.89
Just over 3 1/2 = 3.63
Just over 3 = 3.27

John

[Clive]

OK Bill, fair point but I was trying to keep it fairly simple! Also assuming 4.11 diff unsuitable for planned new engine, looks like a 2litre is going in!

Clive