Disassembled!

[Heuer]

Both involve changing the crown and pinion so the work is the same and both ratios are readily available. My experience of the 2.88 (with a T5 box) is it great at high speed touring in Europe but can be less useful around town as 1st is good for over 50mph and 2nd will take you to 80mph. Either will work for you it depends on how you intend to use the car. This calculator will help you decide on the best ratios for you: http://wahiduddin.net/calc/calc_speed_rpm.htm

e.g:

[1954Etype]

Going to say it again on this forum.... I have a 2.88 and have no problems with it whatsoever. I have just recently changed the ratios in the gearbox for the Series 2 though. Difference is marginal but overall it feels geared like a modern car. I was still looking for another gear with a 3.07.

[Heuer]

There is a difference of about 5mph between a 2.88 and 3.07 diff. Above calculations were done using 5th gear on a T5; here is the result when using a standard Jaguar 4 speed in top:



It does highlight the advantage of having a overdrive 5th gear available - a drop of about 200 RPM; 20mph increase for the same revs.

N.B. I chose 3,000 rpm because it is the sweet spot when cruising in an E-Type. With the hood down we personally find 2,800 rpm to be most comfortable - about 94mph.

[1954Etype]

Interesting comparison David, it certainly felt a lot more than 5mph difference!

[PeterCrespin]

It does highlight the advantage of having a overdrive 5th gear available - a drop of about 200 RPM or 20mph increase for the same revs.

N.B. I chose 3,000 rpm because it is the sweet spot when cruising in an E-Type. With the hood down we personally find 2,800 rpm to be most comfortable.

Erm, my maths isn't that good David, but there is shurely shome mishtake in the above qote? '200rpm or 20mph' implies a gear delivering 100mph per 1000 rpm. I suspect that would be hopelessly over-geared even for the Bonneville Salt Flats :-)

My D-type uses an MOD box with a 2.88 diff,: i.e similar gearing to your OTS. I find it a little too tall even for that super light car, but I haven't had the chance to cross continents in it yet, which is when it would presumably come into its own.

My E-type uses a five speed plus 3.54 so comes out around the same numbers as a normal 4-speed plus 2.88 diff like Angus, but with good low speed (actually, first is too low). This is nice and I agree that 3000 rpm is a nice lope for the XK engine. 80mph cruise suits me fine in the UK. Any higher and you start worrying about points.

[Heuer]

Pete

The facts are all there, though not necessarily in the right order! What I was trying to say was:



or


So a 600rpm 'saving' to maintain the same speed.

[PeterCrespin]

Got it. Reminds me of the old Eric Morcambe line about music notes :-)

[Francis]

This is so very informative! Thanks to you all.

After reading this, and following my mechanic's advice, I will upgrade my existing tranny to a 3.07.

Who sells the parts required to do the upgrade, any body knows?

Barratt does not carry these ratios. They only sell the 3.54 parts for $2400.-...

Francis

[Heuer]

SC Parts sell the 3.07 (described as 3.06) crown and pinion set at ?745. Try contacting Dana or XK's Unlimited.

[1954Etype]

Blimey! Thats expensive! Try UK Axles - they did a good job on mine for a reasonable cost.

[Heuer]

Francis is in Montreal hence my suggestion to try Dana or XK's. The SC price was the only one I could find.