A gearbox for standard drive with a short piece of input shaft on the left up to and including the first gear. That is enough to transfer the torque to the countershaft at the top, where all the gear wheels are firmly connected to it. Below is the second, much longer part of the main shaft. If the first shift sleeve is moved to the left, it connects the two shaft parts for a direct fourth gear, and the third on the other side.

This is followed by a second shift sleeve for the third gear in the left position and the second gear to the right. A main bearing in a transmission wall shields the four gears. This part of the housing is divided lengthways, as was often done in the past. There is now a cover and underneath the straight-toothed reverse gear. Later the fifth gear was added under a slightly larger cover.

As is well known, there is enough space to the rear with this type of drive. Only the cardan shaft needs to be shortened a little. What kind of defects can there be? We can rule out leaks at the front or rear at this stage of the repair because the housing has already been dismantled. If these occur to the rear, the transmission does not even have to be removed. Only the housing parts could be leaking against each other.

This is more likely with longitudinal division than with transverse division. You can try to reseal it with a lot of effort, but in the case of repetition it is difficult in both cases to rework the sealing surfaces. In the case of very rare gearboxes, it may be worthwhile to weld material onto the sealing surface, which in this case is made of light metal, and then process it. Otherwise, the only thing that helps is swapping parts.

There are of course several options inside. Bearing damage can be recognized by noises when turning by hand, gears can be inspected visually, and if in doubt, too much clearance can even be measured. But we're talking about synchronization here. The second gear suffered particularly often with the transmission above, presumably due to a somewhat too violent downshift. This Porsche locking synchronization, which can be seen here, was relatively widespread in the past.

In the VW Beetle, it was abandoned relatively early in favor of Borg-Warner, and Porsche only banned it with the arrival of the 2.4 liter engine in 1972. The one from Borg-Warner is rightly called locking synchronization, which actually does not apply to the one here:

On the far right the gear wheel. The guide shift sleeve must ultimately be connected to this. This means that the shift sleeve, which is non-rotatably connected to the guide shift sleeve but can be moved axially with respect to it, must connect the guide sleeve with the switch interlocking at the end. And precisely for this it is necessary to overcome the synchronizer ring. It is made of heat-treatable steel and is somewhat elastic. It can therefore be spread apart, increasing its circumference and diameter.

Its surface is slightly convex and coated with molybdenum on the contact surfaces with the internal teeth of the shift sleeve. The synchronizer ring is connected to the gear wheel via the blocking stone, the locking tapes and the stop stone. There are now two options for a successful shifting operation. Either the synchronizer ring has its normally small diameter, then it can be easily overcome by the shift sleeve and can even be compressed a little.

The spring action of the synchronizer ring even slightly stabilizes the position of the shift sleeve in the gear teeth. All of this would be the case if there was synchronization between the shift sleeve and gear wheel beforehand. Otherwise it cracks audibly and wear and tear is likely. Now, however, synchronization actually only comes into play when there is currently no synchronization.

Now the shift sleeve rotates together with the guide sleeve and the gear shaft below it faster or slower than the gear wheel together with the synchronizer ring. As soon as the shift sleeve touches the synchronizer ring on the first bevel, it is accelerated or slowed down compared to the gear wheel, which means pressure for the respective locking tape between the stop and blocking stone. This is also resilient and bends more outward.

This movement is also transferred to the synchronizer ring. It spreads, which makes it more difficult for the shift sleeve to overcome it. At the same time, the friction between the two creates a synchronism, which at some point leads to a gear change without a cracking noise. However, as with Borg-Warner, there is no real lock here. So you can try to engage the gear despite the lack of synchronization, which leads to much more friction and wear.

Perhaps that has led to the loss of interest in the Porsche synchronization, despite the sonorous name of its inventor. The stronger abrasion during a repair can also be understood more clearly than a defect in today's locking synchronization. In addition, one complained about the longer gearshifts.