Pro Street Transmission Swing Axle Reinforced 8:31

Pro Street transmission for swing axle, reinforced.
Final drive ratio: 8:31 (3.875).
Swing axle.
VW Beetle.
Type 14 Karmann Ghia.

For light tuning you can easily use the standard transmission, although it is advisable to use a transmission with an 8:31 (3.875) final drive. Volkswagen fitted this as standard in the S versions (with a 1600 cc engine). With this final drive all gears are taller, so a higher top speed is reached.

When power increases considerably, a standard transmission can cause problems. It can take a lot, but keep in mind that it is designed for 50 hp. The Pro Street transmissions are reinforced at numerous points and can be used for heavier applications such as off-road racing, drag racing and track racing. The Pro Street transmissions come with:

- Reinforced side cover (more info: 1493)

- Reinforced differential, fitted with four spider gears (more info: 1420)

- Gears secured with hardened locking keys

- Steel connecting rods instead of cast

- 8:31 final drive (3.875)

- Fitted with a universal gearbox case *

* Thanks to the universal gearbox case, the transmission can be fitted in all model years of the Beetle and Karmann Ghia and is designed for a floating thrust bearing; if necessary an additional thrust bearing with the corresponding pressure group must be fitted (see the standard overhaul transmissions 1490 for more information).

In addition to the modifications above, the transmissions have been professionally overhauled - completely disassembled, cleaned, inspected and fitted with new synchro rings, shift fork bushings and seals. We want to make it as easy as possible, so no core exchange is required. You may need a different thrust bearing with pressure group than the one originally fitted.

Note on the overhaul:

The gears of the various speeds are fitted with an additional toothed ring that ensures synchronization and transmission of the power of the gear being selected. Many overhauled transmissions have lost some of their teeth, whereas this is not the case with the original. However, this is done on purpose to avoid shifting problems. Gears are originally fitted with thin and thick teeth on a crown wheel. Only the thickest teeth are loaded and subject to wear. If these teeth are too worn, the transmission tends to jump out of gear or you can no longer shift smoothly. To prevent this, during the overhaul the thicker teeth are removed so the remaining thinner, less worn teeth can take over. This is only done when those teeth are worn to the point where they cannot be guaranteed to last a whole transmission life. Fitting new toothed rings is unfortunately not possible, as they are simply not available. The "new" transmission is not weaker than the original, because the number of thicker teeth is always equal to or smaller than the number of thinner teeth. This method is used by many overhaul companies and is now an accepted way to solve this problem.

4590: version with swing axle (swing axle).

4591: version with trailing arms (IRS axle).

Note: swing axles are identified by 1 drive sleeve mounted on the transmission side; trailing arm (IRS) axles are separate axles with drive sleeves on both sides.