The taper roller bearing at the 5th gear end of the shaft must be removed to gain access to the 3rd/4th gear synchro cone.
This bearing is pressed on and must be very carefully removed (and replaced) to avoid damaging it.
Really the bearing should be pressed of using a hydraulic press but I don't have one so I devised the following method. After 4 sessions, the bearing remains undamaged!
The main danger is chipping gear teeth. They are very hard and will chip very easily.
Place the input shaft on a piece of carpet in case it falls.
Grasp the 3rd gear synchro clutch housing in your hand and using a very large hide mallet...
...Whack the input shaft HARD until the bearing has moved around 1/8" up the shaft.
Insert a flat bearing puller under the bearing and tighten it until it is just contacting the shaft ensuring that at all times the bearing cage is free to rotate and that there is no contact with the gear teeth below.
Now using a two-legged puller on the flat puller, carefully pull the bearing off the shaft.
Dismantle the 3rd/4th gear components from the shaft.
In this case, the synchro cone (item in middle of the picture) is very badly worn and distorted and can now be replaced.
Reassembly is a reversal of the dismantling procedure. Note that the bearing cage stands proud of the bearing inner race and it is necessary to make up a special mandrel to drive the bearing back without damaging the cage.
The bearing is a very tight fit on the shaft and it is very beneficial to heat the bearing in a low oven (Gas Mark 3) for about 30 minutes. This expands it just enough to make it a slightly less tight fit.
The mandrel was made on the lathe from a piece of hard aluminium alloy with an internal diameter of 25 mm and an external diameter of 31mm. I stepped mine to give it additional strength.
The hot bearing can now be placed on the shaft and the mandrel and large hide mallet used to drive it home.
This completes the overhaul of the input shaft to replace a failed synchro cone.