5 Speed Gearbox: Part-6

The fabricated rear support bracket – Isuzu 5 Speed.

The sheet metal parts.

There is a common belief that the original elan rear gearbox mount can be re-used to support the Isuzu
5 spd gearbox. Unfortunately that assumption is wrong, and true as in the case of the elan S1 to S4. But It is possible with the gearbox installation into the plus two Elan.

In the writers case, the decision was made to build and fabricate a completely new support mount bracket. That’s a lot of work you might think? Well yes, but a very enjoyable project on completion.

With the engine and gear box mounted into the chassis and engine mount bolts tightened to make sure distances are correct, and the combined unit aligned in the chassis, the work can begin.
Using a jack of some kind, the rear of the gear box can be raised or lowered to get the gear change turret at the right height in relation to the top of the chassis rails.

It needs to be mentioned here that the chassis does need to be cut and altered to provide more clearance, the gear change turret is quite a bit larger than the original Ford/Lotus arrangement. Remember, its a five speed, the mechanism is not as compact as the four speed unit.

The required alterations to the chassis (Purists, please look away). Note that there are doublet plates TIG welded to strengthen and maintain the stiffness of the chassis where the clearance and alterations have been made.

See if you can get your head around this. The original rear gearbox mount (Top of photo) leading edge or bridge faces to the front of the elan. The new fabricated mount bridge for the Isuzu GB faces to the rear of the chassis. And there is just enough room by the way. The Isuzu gearbox has two mounting flanges, the front flange mount is used for the Elan S1-S4, but the plus two elan will use the rear most mount. There are no drawings for the design of this bracket, its all eye ball design coupled with trial and error fit up fabricating work. yes, it is certainly possible to CAD and have the bits laser cut, but for just one bracket, in the writers view, not worth the time and effort. far quicker to fabricate, bend, and weld the bits together.

The photo above gives a clearer view of the various sheet metal parts. The welding was done with old school Oxy Acet and TIG welding processes. The support mount bracket is bolted to the chassis using the existing 3/8 UNF HT bolts as that of the original Lotus bracket. As with all none standard installations, there is always more work involved than at first glance. A DIY approach is great if you have a fully equipped engineering shop, along with the required engineering skills.
Detailed sheet metal work none the less, takes a lot of time and effort to get it right, but its certainly doable, and rewarding when you do.

5 Speed Isuzu gearbox: Part 7. (Coming soon)