Sunday, 13 May 2012

DHC’s gearbox rebuild part 3

The last update on the rebuilt of the new gearbox for the DHC (at least I hope so). With the measurements to determine the necessary shim thickness for the main shaft done, the long wait for the shims to arrived began. In the end I decided it might be a good idea to contact the chaps at S&S to see if they could supply the correct thickness shims, which they couldn't. But they were able to supply some oversize thickness shims in. So I could machine them down to the correct thickness. This together with some 0.05 mm steel sheets, enabled me to adjust the main and lay shaft end float properly. In the end it turned out that the thickest off the supplied shims for the main shaft was spot on and the lay shaft needed an extra shim of 0.05 mm to get it spot on.

With the front of the gear box finished I could switch my attention to the rear of the ‘box. Fitting the fifth gear assembly to the main shaft showed me that this also needed an extra 0.05 mm shim to get the end float within the required tolerances. After which fitting the fifth gear selector fork and spool was the proverbial piece of cake ...

Left me with the rear casing, fitting the various seals and oil pump. Turned out that the old O-ring that came out was rather skinny compared to the new one. Explains why there was a small oil leak through the selector shafts hole. But that should be well and truly solved now with the double seal.

But before fitting the rear casing to the gear boxes centre plate it seemed like a good idea to trial fit it, just to be sure. Glad I did it as it turned out that the drive shaft supplied with the new oil pump was incorrect (to long), as a result of which the rear casing just wouldn't fit properly. Luckily the old one that came out was in perfect condition so that was re-used. And with the correct drive shaft in place the rear casing slipped on as it should.

And with the speedo drive gear, rear bearing, oil seal and flange fitted the box now is nearly ready to be fitted to the car. But as it stands now that will have to wait till after my holiday and the International Auto Ecosse.

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