One of the first jobs I had to tackle on my Elan was the erratic speedo behaviour (it bounced enthusiastically ±20mph road speed). The cable outer was worn and had been made to run a tight radius down by the gearbox so it was ready for replacement. There was also a little oil weeping from the angle drive.
I undid the gearbox mounting brackets and gently lowered the tail of the gearbox using a jack which gives sufficient space to see what you're doing. The angle drive dropped out easily as the clip screw was only finger tight! The whole adapter and drive could easily rotate and there was limited pressure on the bearing o-ring.
The speed angle drive looked in generally good condition, span freely and the quill was barely worn. But the speedo cable had been cross threaded onto the angle drive.
- Damaged threads
I had the thread chased out by a local machinist. For future reference its a ¾" x 26tpi British Standard Brass (BSB) thread. After regreasing the drive and installing new paper gasket and experimenting with a fibre sealing washer (5/16" ID, 5/8" OD) on the cable end I've not had any subsequent leaks and the speedo is smooth at legal speeds.
- Angle drive with gasket and fibre washer shown
I hope that is of some use to people on similar predicaments.