diff information needed

[bobbster]

Hi just need a bit of information ,
I have a triumph herald 13/60 that i am converting to a Vitesse , i have already changed the chassis to take the rotoflex drive shafts and suspension.
The problem i have now is the out put flanges on the diff are smaller than the vitesse drive shaft couplings.
So can i change the out put shafts on the diff to suit the roto flex shafts?
Also will the diff be ok, it is a 3.89 or will i need to change it and will i have a problem when i get an over drive prop shaft when trying to connect it to the diff.
And advice would be greatly appreciated  
Cheers Nigel

[Clive]

Are you sure it is a 3.89? it is possible, but would have been a specially built one. All herald (except the 948's) had a 4.11.

If it is a 3.89, or indeed the late 4.11 yiu can swap the output quarter shafts. Or indeed the flange on the rotpflex shafts.

When you buy a prop you can specify what flanges you want.

But do check the diff carefully. All factory 3.89 had the larger flanges.

This will help

http://www.canleyclassics.com/technical-archive/different-differentials/

[bobbster]

Hi Cliftyhanger
Thanks for the info, just been and checked the diff and you are right it is a 4.11.
So are you saying that i can leave the out put shaft in the diff and use the flange on the end of the 13/60 drive shafts and they will match with the flange on the rotoflex drive shaft.
Will the 4.11 diff have an affect on the performance.?

[Nick Jones]

You don't want a 4.11 diff in a Vitesse unless you're going drag racing.  You want at least a 3.89 with a 3.63 being better for a 2L - even if you have overdrive or a 5 speed.

Nick

[Dogsbody47uk]

All the flanges on a 13/60 take 5/16 inch bolts. All flanges on a Vitesse take 3/8 inch bolts. You will need to change the flanges and or the diff. Propshafts are built to your required spec. Cheers, Dave.

[bobbster]

It looks like I will have to change the diff.
Thank you all for your advice
Cheers Nigel

[mazfg]

Quoted from Dogsbody47uk

All the flanges on a 13/60 take 5/16 inch bolts. All flanges on a Vitesse take 3/8 inch bolts. You will need to change the flanges and or the diff. Propshafts are built to your required spec. Cheers, Dave.

My output drive flanges take 3/8" bolts, but my propshaft flanges and the diff input flange is 5/16"
My prop is 4.11:1 Vitesse 6 which is the correct one.

[bobbster]

Being a Vitesse 6 ,is yours a 1600 as mine will have 2000 engine or does that not make any difrence

[mazfg]

Quoted from bobbster

Being a Vitesse 6 ,is yours a 1600 as mine will have 2000 engine or does that not make any difrence

I do have the 1600 engine

[Clive]

I would seriously consider a 3.63 diff if you need to source one. It will be a little more relaxed at speed.

Are you fitting overdrive??

[bobbster]

Yes i have got an over drive gear box. Where would the best place be to get a 3.63 diff from?

[Clive]

If you want a rebuilt unit with a guarantee ten Mike Papworth. Otherwise there is the spitfire graveyard and other breakers, or take a risk with a private purchase.

[bobbster]

Ok i will have to do a bit of searching for a diff and prop shaft, cheers

[glang]

If your going to be running o/d I would seriously consider the standard 3.89 diff. Unless your going to be doing a lot of motorway miles or tuning the engine this diff is perfect as it allows you to hold speed in 4th while going up long motorway hills (its not nice having to drop down to 3rd). Overtaking of course is also much more fun

[Nick Jones]

My 2L Vitesse pulled the 3.63 diff absolutely no problem even when the engine was completely standard.

Nick

[glang]

Guess Triumph got it wrong then but they even put the 3.89 in the lighter more aerodynamic GT6 with o/d.....

[Clive]

Quite possibly!
And to add to that the non od GT6 had the 3.27, which works just fine even when od is added.
Especially when you se the enev lighter and less powerful/torquey 1500 spit had the 3.63

But then again people didn't do long distances or the speeds that we expect today.

[Nick Jones]

Most of the pre-70s Triumphs were horribly under-geared.  Notable exceptions being the TRs, 2.5 PI and non-OD GT6.

It's true - roads were slower and opportunities to hold more than 60mph were quite limited.

Nick

[bobbster]

What diff was put into a mk 2 vitesse as standard with an over drive box

[glang]

Ha I must be stuck in the 60s then as 60mph is good for me n the Vitesse - it just feels right and I get to keep almost modern acceleration

[glang]

They all had 3.89 Bobbster

[bobbster]

Thanks for that's it gives me good idea on what I need
Cheers Nigel

[glang]

Nigel just remembered a couple of other things:
Im running 165/80 X 13 tyres which does make the 3.89 diff a little bit taller. This gives a small speedo error which of course would be even greater with a change of diff ratio. To correct this you need to either recalibrate the speedo or change the speedo drive gears in the gearbox....

[herald948]

Quoted from glang

Nigel just remembered a couple of other things:
Im running 165/80 X 13 tyres which does make the 3.89 diff a little bit taller. This gives a small speedo error which of course would be even greater with a change of diff ratio. To correct this you need to either recalibrate the speedo or change the speedo drive gears in the gearbox....

If your experience is anything like mine over the years, you just might find that your once optimistic speedometer is now a bit closer to accurate with the 165/80R13 tires, assuming that they're actually that much larger in diameter than the OE tires were.

[glang]

According to the interweb changing from the original 155/80 X 13 tyres gives a speedo error of 2.6% while a 3.63 diff almost 7%. Ive never checked my speedo accuracy and your right as I believe their permitted tolerance was 10% so these changes might actually make an improvement....