5 Speed Gearbox. PT 2

Part: 2.
Tail Shaft Mods-Refurbishing
5 Speed Box into Elan.

Tail Shaft Modifications.

Here we go again, concentrating on the minor things. You may think that concentrating on the small things is doing things in reverse, well, perhaps it is, but don’t be too concerned, what this will achieve is to get a lot of the fiddly engineering jobs out the way, and will actually help to speed things up at the other end of the project.

With good reason not wanting to modify the existing elan tail shaft, a visit to a Yesterford parts dealer in Melbourne had me walk out with a second hand Ford Anglia 2″Dia tail shaft, apparently these were also used in the early Cortina. The tail shaft tube in the writers S2 is 2″ Dia (50mm) chro-molly DOM tube, you might also be amazed to learn that the tube wall thickness is 1.8mm thick, and to be honest my original thoughts had me thinking that the wall thickness could have been at least 2.5mm.

There is some considerable re-engineering to carry out with the new tail shaft, being made up of a mixture of Ford/Lotus and Isuzu/Gemini bits that have to be grafted together to make a usable tail shaft, but the aim was to remain with the smaller tube diameter, reason being that the tail shaft tube is offset to one side in the elan chassis, and with a larger tube Dia there is the chance of contact with the chassis, which needs to be avoided.

This universal drive joint (above) of the Gemini/Isuzu is substantially heavier than the Ford/Lotus elan unit, (below) it also accepts a larger tube diameter, so there is a mismatch between the Isuzu and the smaller elan tail shaft fittings, but this will be overcome with some careful engineering. The Gemini uni joints have internal circlips, and the Ford/Lotus are external.

The photo above, shows the familiar elan rear tail shaft to diff yoke and drive plate, it would have been nice if the Gemini and the Ford/Lotus items were a matched bolt PCD, and the inner drive plate locating ring also matched, but unfortunately, that wasn’t the case. So this is where some re-engineering comes to the fore.
You may also note that someone in the past has used an angle grinder to cut seized nuts off, and in the process, they have also removed metal from the outer flange face, this will be corrected during the rebuild.

Dismantling of uni joints can be fun if the right tools are not used. But there are now plenty of moderately priced manual press tools available, that will do the “once every now and again uni joint rebuilding job”.

But it is possible to build almost zero cost DIY tools that will do the job just as well, but they require to be used in conjunction with a hydraulic press, and is the best way to go.

The tools shown above are machined and fabricated from metal off-cuts and workshop scrap, worth about $1.00, but the trade off is, the time taken to make them, but in all reality, its just part of the DIY mechanics life.

Both of the uni joints in this project do require some re-building and machining work which will be carried out before the tail shaft is completely rebuilt with new parts. The measuring of the tail shaft length will also have to wait until the very last stages of the project when the engine and gearbox are re-installed back into the chassis, then the correct length can be ascertained.

The tail shaft tubing is made from Chromoly DOM (Drawn Over Mandrel (Wall thickness 1.8mm) which is very strong. The shaft in the photo above is mounted in the lathe to machine and tidy up the rough cut edge left from the angle grinder. This is about as much we can do for now, the exact length cant be determined until engine and gearbox is mounted in the chassis proper. Although, we have estimated that the shaft will be about 50-55mm longer than the original elan tail shaft, but we are not going to take a guess on that.

Just to complete and finish off part two, the tail shaft, yokes, and new uni joints are ready for re-assembly. But bot until we have determined the correct length of the tail shaft tube, we need to cut, machine, and weld, and then have the new re-manufactured tail shaft fully balanced at the local balance shop.

We look forward to bringing you part three of the series, this will be where we really get into the nitty-gritty of the gearbox conversion process. Watch this space, but be patient.

Continue to part 3.