5 Speed Gearbox. PT 1.

Isuzu Five Speed Gearbox
Modification and Install-PT-1.

Will this 5 speed Isuzu/Gemini gearbox conversion fit into the Lotus Elan?

The short answer is yes… But not without a considerable amount of preparation and engineering work. This is part 1 of a series of blog articles that will detail the preparation and installation of the five speed box into the writers S2 lotus elan

The modern freeway or motorway begs the addition of an extra gear or overdrive on the elan, even though the Lotus twin cam engine was designed to rev freely, a high revving engine can become tiresome when travelling for long distances, hence the desire for that extra fifth gear which will drop the engine revs lower than just the straight fourth gear.

There are few gearboxes which can be shoe-horned into the elan chassis, the requirement is that of a compact design to fit within the narrow chassis box section. It appears that the Isuzu five speed gearbox is an excellent fit, and it just so happens that the gear stick will pop up in much the same spot (10mm difference) as the original elan gear stick, which is a big plus.

But, now the engineering fun begins.

This article (PT 1) will attempt to outline and describe the journey with the Isuzu five speed gearbox installation into the Lotus elan.

But before we begin, we must give full credit and thanks to Max Cain of NZ. Max is the original designer of this unique gearbox conversion and installation into his very nice S4 Lotus elan, one that he gladly admits he is very happy with.

Our Journey is going to begin by tackling some of the small details first.
The Gear Stick – Modifications.

The Isuzu gear stick assembly presents a mystery as to how it was originally assembled, because try as we may, the top part of the stick, which is rubber mounted, could not be parted from the lower part, I guess that’s why they invented the angle grinder, as crude as that may sound which will be used to dismantle the gear stick parts.

There were no pins or threaded parts to undo, the gear stick had to be shortened anyway, so angle grinder it was, to make some cuts around the large tube section to begin the required modifications.

Most of the original parts will be re-used as they are essential to the gear stick operation.

The long tapered and chromed top part of the gear stick will be shortened and machined to suit. The lower part with the ball swivel will be heated (With Oxy Acet torch) and straightened, as will be shown next. (Video)

Please note: We are not able to show every single detail of the general engineering work involved, you may or may not have the skills and workshop equipment or machinery and associated skills to carry out the work involved. You may need the help of others to complete your gearbox conversion and installation project if you decide to journey down this road. I must admit that a few years ago the thought of toying with the installation of a five speed box into the S2 elan was pretty remote…But… well, things change.

And now for the video – PT 1.

What we’ve covered so far is just one small step along the way to the complete conversion and installation of the five speed Isuzu gearbox into the Lotus elan.

Now that we’ve covered part one, we hope to have part two completed in the not to distant future.

It seems that were several different 5 speed Isuzu gearboxes made, but the one to obtain is the box from the twin cam Holden Gemini, these were built in the early 1980’s, the first question asked will be concerning the ratios, below is a screen shot comparing the Isuzu ratios with the Ford/Lotus close ratio box, while not identical, the Isuzu ratios seem to have a nice spread, and the people who have been down this road before are very happy with the swap and the ratios, the extra 5th gear making the elan a very nice long distance touring car without the high engine revs.

As we work our way through this project, there will be more photo’s and written content.
Part 2 is now ready to read: Click here – Part 2.