Jack Knight Twin Cam Heads

[Nathan1293]

The interesting thing is how rough the casting of the gearbox casing is, it has a distinctly rougher gain and more flash marks on the case than standard cases.

I have calculated the wheel speeds using the jkd 6 speed compared to other ratio sets, with a 3.9:1 final drive (that’s what’s it has), 1st is similar to 1st in a close ratio 4 speed gear set using a 3.44:1 final drive. Fifth is approximately the same as 4th in the close ratio 4 speed with the 3.44:1 final drive and of course 6th is a higher ratio.

So you get closer gear ratios with a wider overall spread, which isn’t surprising I know.

[mab01uk]

Many thanks for posting the detailed photos of the 6-speed!
Only ever seen one once on the JKD stand at a Mini show a few years back, as seen in my photos posted earlier in this thread.
It would also be interesting to see the Jack Knight quick shift sometime, if you have any pics.

I have had a Mini Spares 5-speed in my Mini for the past 20 years with no problems, although like most classic cars it has only covered a low annual mileage during that time.

[mk1]

Thanks for the great pictures!

That gearbox is a work of art! Shame the 6 speed never really got into real production.

[Nathan1293]

I believe this is a picture of a Tran-X 6 speed, which was the 6 speed gearbox used by the Rover works teams.

The main difference is 5th is 1:1. 6th being the only overdrive gear.

[Nathan1293]

Jack Knight quick shifter

Notice the modification to the remote, there is no going back to the standard shifter!

shifter_base1.jpg

The bottom of the gearstick and new piviot assembly. The gearstick is in two parts and inner and outer. The outer is tube that is should be set up to mechanically block reverse gear selection. I haven't included a picture, but there is an adjustable plate on the top, should allow the selection of forward gears and requires lifting the outer tube up to clear the plate to select reverse gear.

Shifter_stick1.jpg

A view inside the new mechanism. It all piviots on two bearings, and there is no slack here. You still have the slack in the rollpins connecting the remote rod the the gearbox. I haven't used it but it does feel very nice, hopefuly as nice a the old remote gearboxes!

Shifter_2.jpg

[BAD942B]

Looks like taper roller bearings in the top housing so no play there as there should be preload, could be a super slick shift if there is no play elsewhere

[mk1]

Typical original old school Jack Knight. Superbly "over" engineered regardless of cost.

Shame no one continued the business in the same manner.

[mab01uk]

(Car Choice magazine early 1990's)

[mab01uk]

Sorry for the thread rival, if you’ve never seen a JKD 5 speed box taken apart. Curtesy of Guess works.

Part 1
https://youtu.be/dlR0MdXrdHU

Part 2
https://youtu.be/7Uy8ol5RheQ

Part 3
https://youtu.be/cGfU5Ql4rPg

There should be a part 4 coming.

Part 4
https://www.youtube.com/watch?v=IrU_Ej2QawE

[Miniholic]

I believe this is a picture of a Tran-X 6 speed, which was the 6 speed gearbox used by the Rover works teams.

The main difference is 5th is 1:1. 6th being the only overdrive gear.

It is a Tran-X 6 speed, it’s mine.

4th is 1:1 though, 5th and 6th are both overdrive gears (0.864 and 0.750).

[r.tec]

I took some photos at Mini 40 Silverstone 1999 but I cannot remember where the head of the engine came from neither the gearboxes helical, s/c and dog.

349 (0)_Kopie.jpg

347 (3)_Kopie.jpg

347 (4)_Kopie.jpg

347 (5)_Kopie.jpg

[mab01uk]

The Jack Knight 16V Head. I took the photo at a Mini show where JK had a stand in the 1990's, which was also displaying their 5 & 6 speed Mini gearboxes.

[Nathan1293]

Do you have any other pics of it? Or any details at all. I’ve guessed at what they did to get the ratios as they are.

[mab01uk]

[mab01uk]

(From Wood & Picket Mini Accessories Brochure 2002)