Vit Mk1 2 Litre 3.27 diff

[daverclasper]

Hi. Car, apparently fitted with this, around the same time as a j Type O/D, by Canley back in 2003.

In Haynes manual, it appears only to be originally fitted to GT6's with O/D.

Just wondering if this combination is ok (I understand a 3.63 is the best in terms on reliability and long leggedness), and how strong (or not) this diff is (apparently it was a re con with new Crown Wheel and Pinion)?.

Thanks, Dave

 

 

[Clive]

3.27 fitted to all non-od GT6. And allegedly some OD cars (switzerland rings a bell....)

It has the weakest carrier, but the longest legs. In a 2 litre, and using a vitesse gearbox you should be fine. Recommend changing the oil every few years though.

The gearing could be too long for a Vitesse (and indeed GT6) as you could easily labour the engine if using OD top at moderate speeds.

This canley's page has all the info on speeds etc

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

[NonMember]

As Clive says, 3.27 would be non-OD GT6, with OD either in Swiss market or "to special order", depending which source you believe.

For a Vitesse I'd say it's a bit long, unless all your driving is on motorways (which would be a shocking waste of a Vitesse).

[Steve P]

I have a 3:27 in my MK 1 Vitesse,with a stronger carrier(TR7?).

Unless you do number 11 starts or visit Santa Pod regularly it should be fine.Can`t comment on the gearing as i run a tuned 2.5 engine +big Saloon gearbox.

Steve

[Pete Lewis]

just some thoughts,

i reckon a 3.27:1 is too high ratio, in OD you will need to open the taps more to generate the torque to cruise so you end up with a 

car of slow acceleration and more thirsty  and hill starts need a lot more clutch slip time to achieve take off torque 

3.63:1  is a better all round upgrade for a 2ltr  to keep  within the performance and economy envelope  of a happy vitesse

pete

[Gully]

When I first had my GT6 it ran a D type OD with a 3.27 diff. It was a fabulous cruising car, but lacking on initial pull away. Also, the OD really only got used from 60 mph upwards. I swapped to a 3.63 diff and have never regretted it (aside from being fleeced on the original 3.63 build by a cowboy!). Gives a good balance of acceleration (albeit slower than an original OD car with 3.89 diff) with good cruising revs.

Gully

[Colin Lindsay]

My Mk1 was converted to O/D using a Dolomite 1850 gearbox and J-type but with the original non O/D diff; I find that it's slower to pull away from stationary but seems good through the ratios and of course O/D top is great for relaxed cruising. I tried a Spitfire diff - 3.63 - and binned it after a month. It was quicker to move away but too frantic in higher gears.I like the more relaxed lower revs, and of course higher revs are only the flick of a switch away.

[dougbgt6]

My Haynes GT6 manual says:  non-overdrive 3.89,  overdrive 3.27

Does this error make my Haynes super valuable, like the coins I've just seen on the news? 

My GT6 is non OD, I occasionally think about converting it, but my wallet says NO! However, if I could sell the Haynes? 

Doug

[Pete Lewis]

doug  its a haynes typo  so not worth much ,   G VIII  is a better bet to  build the pension  Ha !

Pete

 

 

[dave.vitesse]

The Vitesse is a heavier car than the GT6 hence the 3.27 is too high geared. I agree the 3.63 is the best bet. The Vitesse replacement, Dolomite 1850, used 3.63 with or without O/D.

Remember it's a close ratio gearbox, which means the first gear is quite high to start with when using the standard 3.89 diff.

Dave

[Steve P]

8 hours ago, Pete Lewis said:

doug  its a haynes typo  so not worth much ,   G VIII  is a better bet to  build the pension  Ha !

Pete

 

 

Or even Edward VIII.

S

[Pete Lewis]

steve  its me pills  

Pete

[Clive]

There does seem to be opposing forces at work amongst Triumph owners. 

One is the whole thing about having long gearing, so keeping revs low. (this does not necessarily make the car more economical. John Kipping did a lot of research and found on a Herald with OD the 4.11 was the most economical. At least that is my memory of his article. But that is probably why the factory chose the 4.11 as the most suitable ratio?)

Second is the cult of buying sports exhausts/manifolds/filters etc etc that have the purpose of making an engine more powerful (fingers crossed!) but that power is going to be almost entirely at higher revs....

There was a nice story/letter many years ago in the courier. An owner had decided that he wanted a 3.27 diff in his Herald. So fitted one, only to discover it was utterly hopeless and 4th was unusable to all intents and purposes. A change back quickly followed.

I would say that the 4 cylinder cars, the 4.11 does suit the 1300 really well, and indeed the 3.63 works incredibly well with the 1500. I ran my 1500 Toledo with a 4.11 diff and overdrive, and that would sit at 5000rpm in OD top quite happily, and offer good allround performance. The engine was fully balanced though, otherwise the 5000rpm would have been pushing it for continuous use.

The 6 cylinder engines are torquier than the 4 cylinder, so it is surprising that the GT6 was fitted with the 3.89, the 3.63 really would have been more suitable? But I can see the heavier Vitesse, also more likely to be carrying heavier loads, requiring teh 3.89. Both should have been equipped with OD as standard, but I guess even then keeping the prices low then adding extras was the way selling was done.

Anyway, enough waffle. But I should add that my spitfire with its modernish engine was originally fitted with a 3.7 diff, but I found it dropping out of the power band when changing from 2nd to 3rd, and indeed 3rd to 4th. So changed to a 3.9 which restored harmony. I then swapped the engine to a variation that had a wider power/torque band, and swapped back to the 3.7 So really ratio choices are down to what you want to achieve, you really cannot have quick acceleration and relaxed cruising. Well, OD or 5th gear can help towards that aim, but ultimately if you want sports car performance you want more revs... And somewhere you have to make that compromise.

[Peter Truman]

Two queries, I never understood why Triumph fitted a 3.27 Diff to the Switz GT6's with all those mountains surely a higher diff would have been more suited. Secondly the 3.89 diff in the GT6 was that the old American desire to be the first car away from the traffic lights.

Peter T

 

[dougbgt6]

Most of the population of Switzerland live on the central plateau, which is, well, flat. Perhaps that’s all the research Triumph did? 🤓

Doug

[NonMember]

Gearing of production cars can be affected by things you might be overlooking. At least one market (French?) Rover 820s had special gearing because of the way tax is calculated there.

[mpbarrett]

interesting discussion.

I have a 1500 Herald with a OD gearbox with GT6 close ratio internals so first is quite high, I have also fitted a 3.89 diff. All seems to work quite nicely.
My 1500 engine has a Newman's basis cam which I choose for a the wide torque band. It also has EFI and electronic ignition so has a very smooth flat torque response
which is what I wanted (its a 1500 so does not really like to rev above 5000rpm). I am really pleased with it, quick enough around town and good on the motorway up to 80/85 without any stress. It does come alive from 3750, I rarely take it above 5000 overall it does everything I wanted. And cruising around 70mph and it will return over 40mpg on a run, 

BTW  I think its great that  we are able to play with gearboxes, diff ratios etc,

Mike

[Steve P]

My two cars..This is what i ended up with after playing with gearboxes,diffs etc.

Vitesse MK 1 ,2.5 engine with Saloon box and J type O/D.3.27 diff.

1st Gear is a little short but the car pulls like a train and 80 mph in O/D top is comfortable,i took it to over 100mph once but it was scary in a convertible 50 year old car.

My Herald has a tuned 1500,single rail O/D box and 3.63 diff.Really nice car to drive and cruises easily on the motorway.CV conversion is the next job along with rebuilding the front suspension and fitting 4 pot calipers.

Steve

[daverclasper]

5 hours ago, Steve P said:

Vitesse MK 1 ,2.5 engine with Saloon box and J type O/D.3.27 diff.

Hi Steve. I think my revs are sort of half the speed (speedo not that accurate). eg, 3,500 rpm, at 70 mph, in O/D top.

Are yours similar?.

Dave

 

Edited January 18, 2020 by daverclasper

[Steve P]

Hello Dave,

I converted to an electronic speedo and rev counter,mainly due to the Saloon box speedo drive connection position.

70 MPH according to mine is just under 2900 RPM in OD top.

80 is just over 3k revs.

Steve

[daverclasper]

Thanks Steve.

Cars standard 2  Litre and doesn't seem to struggle with over high gearing to me, in/out of O/D (though never driven another to compare), though maybe a bit sluggish going up steeper hills in higher gears .

Seems mine is maybe different to yours (by the comparable figures,) as maybe mine lower geared, somewhere, maybe good, as haven't got your extra BHP.

My O/D apparently was off a Volvo originally, and heard they can have different gearing?

Dave

 

   

 

 

Edited January 18, 2020 by daverclasper

[NonMember]

15 hours ago, daverclasper said:

Hi Steve. I think my revs are sort of half the speed (speedo not that accurate). eg, 3,500 rpm, at 70 mph, in O/D top.

The standard gearing with a 3.89 and O/D is 21mph/1000RPM, which is what you're seeing to within the margin of error of the gauges. Changing the diff will obviously affect this in real terms but makes no difference to the gauges - your speedo just becomes (differently) inaccurate.

[daverclasper]

 

On 19/01/2020 at 09:50, NonMember said:

The standard gearing with a 3.89 and O/D is 21mph/1000RPM, which is what you're seeing to within the margin of error of the gauges.

That's odd, as looking at the Canleys rpm/mph figures, it could not be 3.27 I have.

The cars history from before it was fitted to when I bought car, seem regular and comprehensive.

I wonder if a mistake was made on the invoice, as Canley would have had a good idea of what was suitable?.

Cheers, Dave

[johny]

To add another factor into the mix, I like to get my standard Mk1 Vit into 4th gear as early as possible because thats the quietest and most robust gear. To do this I find the 3.89 diff perfect as I can pootle round town in 4th down to 1100rpm and it'll still pull from there with no problems....

[Clive]

You need accurate speed (sat nag) and revs (not cable rev counter, often inaccurate)

Or jack one rear wheel up, mark with chalk, mark prop with chalk. Do 2 full wheel rotations, count how many times the prop turns. That is your diff ratio.

Speed can be out if the wrong speedo drive is fitted inside the od, or wrong speedo.