My 1965 3.4 ltr “S” Type has the fully synchromesh gearbox and is fitted with 185 x 15 tyres.
I use the transmission in exactly the way it was intended, that is running in overdrive at cruising speed only to reduce engine RPM. If I meet other traffic and wish to overtake I drop out of overdrive and accelerate in 4th gear. I find adequate torque for that kind of use.
Obviously if you re-gear the axle in order to reduce engine speed, say from 3.77:1 to 3.31:1, then the car will lose some flexibility at lower speeds. In my case the original idea was to choose a ratio that would allow a good fuel range and easy cruising in Continental Europe, not particularly in England where I live. Unfortunately, two bouts of cancer put paid to very long Continental journeys, but Ireland and France are doable. In fact I conducted the initial shake down of the car with a 3.77:1 axle in both France and Ireland.
It is fairly easy to pick up second hand 3.31:1 gear sets in UK /Europe as they were original to E Type and those owners generally try to upgrade to 3.07:1. The standard E Types for North America had the 3.54:1 gearing, which would normally be my weapon of choice for an overdrive “S” Type car.
At the time I rebuilt the rear end on my car I had availability of a new 3.07:1 (still have), or a second hand 3.31:1 set. As I had all the hypoid gear ** **setting equipment and connections to lap the second-hand gears after I had fettled the teeth, I chose the 3.31:1 set. This was eventually fitted into a (LSD) limited slip differential, my original was none LSD………..don’t go there with the “S” type, use an LSD axle.
**In semi-retirement I had built up and owned the operation that rebuilt the majority of early post war Rolls-Royce Silver Cloud axles and some military hypoid drives. Although building hypoid axles were well within my pay grade, due to illness I had to get an acquaintance who specialised in Jaguar axles to rebuild mine with my supplied gear set.
Having chosen the 3.31:1 gear set it does work quite well in England, especially in my locality and I can drive, even around traffic islands in 4th and use the overdrive for the open road. The city here has the second largest collection of traffic islands in the UK, (hundreds) each demands a “give way” but not an actual “stop” as in the USA. These traffic islands can be negotiated in 4th gear with the 3.31:1 axle easily as engine is very tractable. If I need, fast away, or rapid overtaking I use the gearbox, that is its function. Country lanes are not a problem and the 3.4 ltr is a nice flexible unit and definitely enhanced with an LSD axle at the rear.
As I have tried to illustrate above much depends on “horses for courses”, the terrain and journey distances. If I were re-gearing an “S” Type overdrive model for use in England only I would use the 3.54:1, if it were for use in Scotland or Wales then I might consider leaving the 3.77:1 in situ to handle the terrain. In the case of the USA I think anyone travelling inter-state often may consider the 3.31:1 ratio.
The original ratio of 3.77:1 allowed good acceleration but demanded use of overdrive for even relaxed local driving, in short very under geared and very tedious to drive. We need to remember that road structures and gradients are much different from those when the cars were built and not everyone is interested in flat out acceleration or the resulting noise when that happens. I was trained in an environment where good automotive engineering was judged by the driver not knowing how fast he was travelling. Furthermore, I value the ride and roadholding more than shear acceleration.
Hopefully I will be able to attach here a chart showing all the other details you requested, I trust it may be helpful. Based on 82% series Michelin tyres at 785 rev per mile.
You might notice that the UK national speed limit is 70 mph and that speed in 4th gear drops right on the engine maximum torque at 3000 rpm with the 3.31:1 axle. Running at 70 mph in overdrive leaves the engine turning nicely near the bottom end of the useful torque band (2500-4000rpm) whilst disengaging overdrive places it exactly on maximum torque at 3000rpm.It is also within my self-imposed engine piston speed limit of 2500 ft per minute at 3594 rpm.
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