5 speed vs overdrive

Just to add more information, a few months ago we had a 66 Coupe which had been fitted with a Toyota W58 5 speed. The conversion kit was made by Dellow Engineering in Australia and it was a very nice box. We resealed it and fitted a primary shaft bearing with of the shelf parts from a local dealer.

I looked through my 3.8l Owner's manual, and it has this to say:

3.07:1 - 60mph @ 2398 rpm
3.31:1 - 60mph @ 2618 rpm
3.54:1 - 60mph @ 2775 rpm

The 3.07:1 was generally for the European market. The 3.31:1 was for the US/Canadian market to begin with, then changed to 3.54:1 as standard around 1963, but you could order the car with the ratio you wanted. We have a local 1964 Canadian car with a 3.07:1. You could also order a 2.94:1 ratio, but that one is no longer available it seems. My '64 has the 3.54:1

The simplest way to find your diff ratio, is to look at your speedometer, unless it has been "tampered" with. Just above, and to the right of the needle spindle, and the Smiths part number, there is a number. They are:

1120 for 3.07:1 (700 for kph)
1216 for 3.31:1 (760 for kph)
1312 for 3.54:1 (820 for kph)

I found a wreck of a 1968 FHC that looked like it had a 3.54:1 ratio from the diff tag, but on counting the crown and pinion teeth, it had been changed to a powr-lok 2.88:1 set. I'm keeping that one, along with the re-calibrated speedo that came with it.

Cheers, Mark R.

Ron, just put a dab of Snopaque or paint on the front flange of the diff and count how many times it goes round for one full turn of the back wheel (both wheels off the ground and the gearbox in neutral.) That will give you the ratio. So will looking at the brochures on Jag-Lovers for your model.

John, who's talking about a Series 2? Every car in this thread has been a Series 1, except maybe the S1.5/68 of James.

Besides which, the switch to 3.54 happened long before the Series 2 came out.

The series 1 could do 150 mph off the showroom floor, 0-60 in 7 seconds and a 15 second quarter mile. One wonders why you would want a different transmission. When Jaguar bowed to the auto engineers in the US Congress and removed the triple SUs and replaced them with the egregious Strombergs for the series 2, they put in the 3:54 rear in a tepid attempt to regain some semblance of sportiness, producing a 120 mph car that took 3900 revs to go 70.

Save your money.

Great information about transmissions, overdrives, and rear-end ratios. Always look at cars on xkedata when VIN is available. Rudy's both look great. Ron, we'd like to see your car also. I used to have a 63 coupe but sold it in early 80's to keep first wife happy. Didn't work. New wife likes the 68 roadster I recently purchased (1E17044).

Rudy,
I have had my 66 E-Type OTS 1E12929 for 33 years. Very close to yours. How do I determine if the rear-end is a 3.31 and if not are they available?
Thanks

Raising the rear-end ratio to original factory specs (3.31)(?) makes the 4-speed a delight to drive. Third gear brings out the torque and range mentioned in all of the test drive revues from the sixties. The 3.54 ratio used in the U.S. spec cars made the cars faster off the line, which may have seemed important then, but hurt the high speed 'grace' of the original.
Changing the ratio in my cars back to the way they were designed to be turned out to be the most enjoyable choice I've made.

Rudy Hatcher
66 E-Type OTS 1E12953 34 Years
66 E-Type OTS 1E10795 30 Years

Welcome Earl. I went past Mildenhall the other day on a visit to the guy who is building my fortcoming D-type tub in the next village. I used to work in Mildenhall for a couple of years and knew some people on base. Those were the days when the Blackbird flew regularly out of Mildenhall, which was a sight to see :-)

I can only show you an OD box in my current D-type but to be honest there's nothing to see in an E-type - it all just bolts in exactly as stock in a LWB car. The only thing to see is an extra few inches of alloy casing at the back. Of course if Uncle Sam lets you ship stuff home cheap, I have several OD boxes you could have! :-)

Pete

Thanks, Gents!
I keep hearing wonder tales about the 5 speed, but the price keeps putting me back. I'll give Medatronics a look tho.
Pete- The USAF is moving me to RAF Mildenhall this June which appears to be in your neighborhood. Maybe I could see firsthand an OD conversion? Also, are you going to Silverstone?
I love this Forum!

Any long wheelbase E-type (i.e. any 2+2 of any series, plus the V12 OTS) will fit an XJ6 overdrive box with zero modification to the car. Absolutely zero. Same mounts, same drive shaft etc.

Many in Europe do this because we have lots of XJ6 overdrive gearboxes whereas you don't in the USA. An MOD box is also bout 15% of the price of a 5 speed conversion, so that's another reason...

The only change you need to do if you have a manual car already is swap the tranmission tops between your existing box and the overdrive box. This brings the gear lever out in the exact same place as the E-type.

If you are converting an auto it doesn't matter as your trans tunnel is different anyhow and there are no stock console parts to match, so the lever coming out about 1.5 inches further back is not an issue. In fact it's nicer that way from a driving perspective if you have long legs. If you want to adapt a manual console to fit on your larger auto trans tunnel then yes, you'd need the E-type gearbox top cover (same as the early S-type IIRC). You could modify the XJ6 cover instead if you wanted to, by chopiing off the short rear extension and rewelding or even bolting up the stub onto the rear of the top cover.

There was insufficient length in the original E-Type tunnel for an overdrive. The longer 2+2 may or may not allow it, but Jaguar chose not to try. If it could be done, it would be cool to relocate the horn to the center push, and use the turn signal button to activate the OD. Thank goodness I don't have time or money for a new project!

Earl,
George is correct in outlining the specifics of gear choices vs. rear end ratios. He also seems very pleased with the unit he installed.

The number of choices avaiiable is why I suggested for you to talk to Paul at Medatronics. He will know what to recommend for your car better than anybody. He builds these things and will know exactly what is best for you.

Hi Earl.
I've never heard of an OD unit installed in an E-type, but that doesn't mean it hasn't been done. I also installed a Medatronics T5 in my '65 E-type. It makes the car driveable at modern highway speeds. The 3.54 rear axle ratio in the cars that were exported to the USA results in very high rpm in modern highway traffic. But my point to you is that there's more to it than simply "installing a 5 speed". There are some choices to be made that if you don't make them right you won't be happy.. First, there's the choice of the first four gears in the box. I don't know how it is now, but when I installed mine there were two choices, a so called "close ratio" box whose ratios are very similar to the existing Jaguar gearbox, and another version that had very low first and second gear ratios. You want the close ratio version....avoid the box with the lower ratios! Second, there's the choice of the fifth overdrive ratio. There are many choices available from .60 t0 .90. I chose 0.73. It works great. I wouldn't suggest anything lower (numerically higher). Good luck!

George Parker 54 XK120SE OTS S674881
65 E-type FHC 1E31486
96 XJ6 06 XJ8L

Earl,
I do not know about OD for E-Types, but I have a Series 1 roadster with a 4.2 engine and have replaced the the 4 speed synchro with a JT5 trans by Medatronics. It is not cheap, but it is GOOD! The fit into the car has the shift lever come out right where it should, and if you are worried about originality if selling, just hang onto the original trans.

The JT5 is of very high quality and smoothness of operation and lays those rpm's way down at 80 on the highway. Talk to Paul at Medatronics.

I'm not $ associated with Paul but just a highly satisfied customer. My car is # 875864 on XKEDATA. Howard Bollinger