Triumph Diff

[vixen]

I have a Triumph diff. with the following numbers on it
FH 21774 / V2734 / 88311425 It is a 3:89 diff.

I know this diff was used in Spitfire MK4 and GT6.
i have been told that the spitfire diff. used a stronger crown wheel.

Is there a way to identify from the outside if it is a Spitfire or GT6 diff.?

[//j17]

The serial number doesn't really tell you much - just that it's a small Triumph diff with a round front pinion flange and 3/8 bolts all round, fitted to either Spirfire Mk IV/US Spitfire Mk IV/US Spitfire 1500.

It's almost certainly going to be a UK Spitfire Mk IV diff, but the real tail-tell will be the ratio and the easiest way to find this from the outside is to count the number of turns of the input flange to turn either BOTH outputs 360 degrees. You will end up with one of these:
4.11 (just over 4 input turns) - US Spitfire Mk IV
3.89 (just under 4 input turns) - Spitfire Mk IV/US Spitfire 1500

All that said there is no difference in the strength of small Triumph diff crown wheels - just their ratios. Some of the rarer ones have other weaknesses - G/Y/GA/FC diffs (early Spitfire/Herald) for example have thinner quater shafts.

[vixen]

Thanks for the info. The ratio of my diff. is 3.89.
If I am right the later GT6 also used this diff.

My diff. has six holes on top for holding the springs.
Do you know if the Spitfire MKIV has four or six holes on top?

Edited by vixen on Monday 22 December 10:21

[//j17]

vixen said:

Thanks for the info. The ratio of my diff. is 3.89.
If I am right the later GT6 also used this diff.

My diff. has six holes on top for holding the springs.
Do you know if the Spitfire MKIV has four or six holes on top?

Edited by vixen on Monday 22 December 10:21

Six bolt holes in the casing means it's off a non-swing spring car (Herald/Vitesse/GT6 Mk I/Courier van) but none of those would have had a FH prefix (G|Y|GA|GE/HB|RA|FD|HC/KC/GA respectivly).

I think what you have is a bitsa. At some point the diff has been reconditioned with an early (non-swing spring) rear casing and a Spitfire Mk IV nose piece (where the serial number is stamped).

Given the ratio I'd guess a non-overdrive GT6 diff.

Edited by //j17 on Monday 22 December 11:36