4000rpm or get a 5 speed...?

Jeez, one day this guy is new to the Forum, the next he’s talking heresy about 5 speed gearboxes….

I don’t plan on this car being a Garage Queen, and living in California there’s going to be a fair amount of freeway time. Whilst I certainly intend to drive with due reverence, as points of reference I’m used to wafting along in a Supercharged Range Rover or screaming along in a Maserati GT Sport Convertible, and just keeping up with The Wife in the former yesterday I find myself, obviously, at 3000 - 4000 rpm. Would have been 5000 had I not let her disappear off into the distance.

This would all be fine in the Maserati (in fact it sounds awesome and I do it deliberately!) but I fear less ideal in the E.

Is the conventional wisdom that the venerable Jaguar 4.2 can run at 4000 rpm all day, or that I should be hung, drawn and quartered for even asking the question and should drive at a more sensible speed?

(As a Magistrate once asked of me: “What can you possibly have to say for yourself that could begin to justify driving at speeds more appropriate for the racetrack than Her Majesty’s Public Highways…”?)

And what are our thoughts on 5 speeds…?

Again, please forgive the heresy, just finding my feet here.


5 speeds are nice, I think. But, I also think that the XK engine well fettled can run at 4,000, 4500 all day; 5,000 is not damaging for a while. Same engine basically as used in the D-Type. I drive to Palo Alto to Monterey at 4,000 RPM about every weekend. Also note that the engine runs very quietly at 3,500-4,000 RPM, quieter than at 2,800.

But I’d get a 5-speed in my second E-Type (if any). Please yourself!

Also, lower numerical axle ratios (than your 3.54:1) are available much cheaper than a 5-speed; 3.07:1 was a standard unit for Europe and some other places. Will get you a nearly 150 MPH top speed, at the cost of maybe a second and a half to 60 MPH.

[edit:] The most recent jump in performance has the E-Type slower than lots of modern "little’ cars, like the Subaru WRX and the Honda, the Maserati is going to be way faster!. Don’t try to out-drag them or even keep up! Have your wife follow you.


Yeah. I know from which you speak old boy. I can’t help myself when I’m behind the wheel of my GMC diesel pickup. Once that turbo kicks in it’s hold on for dear life. All kinds of power on tap. Is your Maserati a pickup?

4000 rpm with 3.54 gears puts you around 90 mph-ish. Noisy 90 mph-ish, mind, but just over the peak power curve for the engine and nothing it can’t handle. Regardless my honest perspective is the E would benefit greatly from a 0.75-ish fifth, particularly for those who enjoy highway driving.

Yep, not looking to turn the car into a drag racer at all, just thinking of how best to tackle a steady 70-80 on the Freeway.

3500-4000 rpm feels a bit frantic and I feel terribly guilty at the abuse i’m giving the poor old girl, but if she likes it then fine.

Rob you might find this book useful. It is a short interesting read by a guy who used an E in the 60’s all over Europe in all kinds of conditions from high traffic roads to wide open all day cruising with no speed limit. They are pretty common to find for not much $$. Best book I have found so far to give a feel about how they behave with different stock axle ratios and conditions.

68 E-type FHC


4000 RPM continuous surely couldn’t be considered abuse of this great engine, but if this is a common occurrence for you, I’d STRONGLY suggest a 5-speed. I love mine. Beyond engine concerns, it’s just a lot quieter and more relaxed.

The problem right now (from the forum posts —) seems to be availability. Paul C. in Florida (5speeds.com) is surely the great old standard (that’s what I have), but apparently they are in short supply right now, as are the others. There is a recent thread on “the driven man” conversion, check that out.

You will never regret going to a 5-speed. It’s just money, and that is soon forgotten.

Bob Frisby
S2 FHC, Boise Idaho

I ran a modified E Type with an oil temp gauge for a few years, occasionally on track with it, then added an oil cooler. Raced an E Type for 15 years with oil temp gauges, always with an oil cooler. My view is that the XK engine can handle 4000 rpm + without an issue, but at that rpm and higher you need an oil cooler. Much of the heat in oil comes from the thrash of the pistons rods and crank, working through the oil that is spraying everywhere. Oil temperatures starts to rise into uncomfortable levels at the 4 k rpm region.

Jaguar tested their own 5 speed in the late '60’s. They had hoped to have it ready for the last batch of 4.2’s, and have it fully tested and ready for the Series 3 V-12. Sadly, British Layland were in dire financial straights, so no 5 speed. What does this tell you…nothing any manufacturer would like more for the long term health of their engine, then to have it run at lower rpm’s, when possible. Some MB models offer a 10 speed. Modern Formula 1 cars run a semi-automatic 9 speed.

If you can secure one, do it ! I put one in my 1973 over 10 years ago…best thing I ever did. Different car…smooth, quiet, better gas mileage on long trips…its a win-win all around. And, if and when that sad day comes, and you must sell your baby, 5 speeds bring a premium. Good luck !

Rob, I went through the same scenario in my 71 Ser 2, for many years… reaching for the ghost 5th gear. When on the highway at speeds of 70 plus, the engine was wailing, begging me to shift, but with 3.54’s in the pumpkin, no chance.

I talked with others on the forum, 5 speed? different ratio change, etc. But after much deliberation I settled with a crown and pinion change. The 3.54’s were out and 2.88’s from an XJ6 installed by a local “diff only” shop. I gave them the pumpkin, they did the change, set up the lash, new seals, bearings etc.

It made the car. It now cruises very comfortably at 2500 rpm for 65 mph and the spectre of the car being a slug at take off did not materialize. The triple SU’s helped that corner of the equation. Of note, being in Canada we use Km’s, not MPH. I did not bother with the speedo gear change, the difference is 20% so I just double what the speedo says…30 mph = 60 km’s. It is very close and the police agree. It is a more affordable alternative and an easy conversion. best regards, Brian / Mytype

Stick a 2.88 in from an old XJS or Saloon. Its dead easy and cheap. You will not lose much in acceleration, it will reduced motorway revs dramatically and can easily be done in a weekend. Buy one on good condition that it not leakink, swap on your e type cover and diff brackets.

Also you will not have any issues servicing /repairing the low volume specialist 5 speed parts and you can keep the rest stock.

4 gears is enough for a light car with a huge motor.

I did it a year ago, went from 3.54 to 2.88 in an S2 FHC, it is brilliant and cost £400.

I was driving it yesterday, its a peach.

As mentioned, the rear end ratio swap is a no brainer if you want an affordable and easy fix. I did both the ratio change and 5-speed box in my OTS. I did the rear end ratio change in my automatic transmission 2+2. Like you, I found the high revs absolutely intolerable. I can cruise at 65mph on 2100rpm all day in my OTS, and the 2+2 is more tolerable at 65mph on about 2400rpm.

Rob, if you poke around on the 'net you will find multiple records for speed and endurance - notablly in 1952, a 3.4 litre XK120 that ran at over 100mph for a week - expect that was well over 4000rpm. You’re car is in good company. Paul

In its day, a great promotional test. No doubt a capable engine. But we are talking about an individual who pays all the maintenance bills on his personal Jag, plus the additional cost of fuel when running with high rpm’s , when you could go from A to B , same speed, with considerable less fuel burn, and wear and tear on the engine. No doubt this test, way back when, had funds, from Jag, or others, to pay for the fuel, and the tear down that followed such an extended test. No such thing as a free lunch…any time you can run any engine and use less rpm’s, this is a VERY good thing. rear end ratio, or 5 speed box, its a step in the right direction. FYI, for a 5-speed try Driven Man in Tenn.

I get a lot of highway time on my 3.54:1 equipped car, and my highway fuel usage (~20 MPG US) is right up there with people who have long axles or 5-speeds.

4000 RPM running is a lot healthier for the engine than slow city driving at low RPMs, short trips, or sitting in a garage. It’s what the XK engine was designed for. 14 years, 60K miles, no major engine expenses.



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My engine was last rebuilt in 1976 and I know it was not rebuilt well.
This engine has had a lot of abuse high rev auto cross and cross country trips at high speeds and engine keeps going strong. I even had a oil pump that was cracked and ran it that way for years ( it ate a cotter pin). My gas mileage at best is 18 mpg and have been trying to lean out mixture to improve mpg. Fine tuning Stroms with adjustable jets and use of on board O2 sensors, will see if mpg improves on BSOL.
How Jerry can get 20 mpg is exceptional. I remember getting 21 mpg on a fuel economy run in the 70s, but that was with a lot of coasting.



I got a measured 21.6 MPG (US) on the SOL (Southwest Oil Leak, 2011) over the whole trip of almost 3,000 miles. 22.3 MPG over the NWOL (North West OL, 2012) over 2,500 miles. It’s dropped to about 19.7 since I installed EDIS – not the EDIS but my tuning is worse, I guess. (COL 2013, 19.8 mpg; WTXOL 2014, 19.7 MPG) And I drive 70-75 MPH with energetic acceleration!


Agreed. When I did the engine rebuild at 64K miles there was very little evidence of wear, the most significant being in the timing gear. There was a very slight showing of copper in the upper, rearmost main bearing all others - mains, rod and cam bearings - otherwise normal grey. Cylinder wear was half a thou to one-and-one-half thou with no top ridge.

I’ve driven a tri-carb S2 plus two with 2.88s in the rear and while acceleration and throttle response was acceptable it did not compare to what my 3.54-geared OTS delivers, recognising the contribution of extra weight in the 2+2. It really comes down to how you enjoy your car. I like twisty back roads. I rarely drive with the soft top up so it’s loud anyway, though I admit on the highway in the spring and fall when I’ve got the hardtop mounted and the windows rolled up I’d appreciate an overdrive gear.

But there’s no way I’d give up my 3.54s for 2.88s

There is obviously no single right answer, and like politics I don’t think the 2.88 or 3.07 advocates are going to sway the 3.54 fans, or vice versa.

That said has anyone ever put together some kind of list that shows which Jaguar years and models came with which pumpkins and gear ratios that are a drop in replacement fit for the standard Series I and II E-type rear end?

I ask because I’m considering going with a 3.07 and am looking for a direct drop in replacement. I know I can pull the differential and have the gears changed but I think I’d rather have a second pumpkin with the 3.07s that I could drop in in a day.

Yesterday I made a modification that you guy are going to have a good laugh about.
Remember back in the 70s some cars had “RamAir” or Shaker Hoods, well my E now has ram-air also haha. My 70 E has the rectangular air filter that originally took hot air from exhaust manifolds at warm up to air cleaner. I now ran a hose (swimming pool cleaner) to a shop vac attachment to collect air below bonnet. Will see if this leans out mixture or not.

Be kind

Here are pages in my book that compare the 3:07 and 2:88. His was a '66 4.2. I have at times thought about switching to a 3:07 since I originally thought my 4.2 had plenty of torque and the longer highway legs would be nice to have but now think with my 3:54 is probably best for me living in downtown Houston. Still want to ride in a 3.8 sometime to see how different E’s are with the freer revving engine.

68 E-type FHC