020 Transmission 5th Gear Conversion

As everyone with a '83 or '84 GTI knows, the close-ratio transmission that came stock with the car is geared pretty low.  If you drive your car on extended trips, the constant droning of the engine at highway speeds can become pretty tiresome.  This is not particularly a shortcoming, as the original GTI was praised by the motoring press as having perfectly spaced gears, but being able to cruise at 70 mph without abusing your ears is a plus to some.

There are a couple of ways to fix this problem, one of which is to replace the transmission with a wide ratio unit from a garden-variety Rabbit or Jetta.  If you've modified the engine to the point where you've got plenty of torque and power, then this is most likely the easiest route to take.  However, if you're at the point where you're working with a stock engine, or one with the basic bolt-ons, then leaving 1st through 4th alone and replacing the 5th gear with a .75 unit may just be what the doctor ordered.  In this instance, your acceleration will be preserved for the usual stop light battles, but you can cruise with pleasure on the highway.

So, what does the .75 conversion do, you ask?  Well, it drops the engine RPM while in 5th by an additional 500 rpm or so.  This means that there will be about a 1000 rpm drop between 4th and 5th gears, so if you shift from 4th at about 45 mph (approx. 3,000 rpm), you're going to be dropping your engine down to about 2,000 rpm.   In an area with a 45 or 50 mph speed limit, this is somewhat annoying.  Where the dividend shows up is on the highway, where 65 mph is at about 2,900 rpm.  

So, the big question is: "How do I swap my 5th gear?"  Well, you've come to the right place.  For starters, this conversion can be done with the engine and transmission in the car, but in the long run, the best way to do it is with the transmission pulled.  The side benefit is you can replace the crankshaft main seal, clutch output shaft seals, pressure plate, clutch disk etc. while your at it.  The dangerous part about performing this task with the transmisison in the car is it is very easy to let the 5th gear selector rod slide out of it's tube, letting the shift forks inside the transmission fall out of place - then you'll have to pull the transmission, take it apart, and put everything back in position.  

The conversion kit should come with the gear itself, a special tool, a sychronizer bolt, thrust washer, circlip, a gasket, and a new transmission end cap.  The last time I checked, the cost of this kit was about $230.

When reading the procedure, refer to the exploded view of the transmission below, and you'll have a good idea of what I'm talking about.  At this point, I'm going to assume you've got the transmission out of the car or in a position where you have access to the small end of the unit.  This is where the 5th gear is located.  Set the transmission up where the bell housing is pointing down, and the narrow end of the transmission is pointing straight up.

DURING THIS WHOLE PROCESS, REMEMBER - DON'T LET THE 5TH GEAR SELECTOR SHAFT FALL OUT OF THE TRANSMISSION!

1. Put the transmission in neutral.
2. Remove the transmission case end cover.  This is the part of the transmission case with the green "cap" pressed into the end of it.  Once off, you'll see the 5th gear selector shaft and tube, the 5th gear sychronizer (which has a fork wrapped around the selector tube, and is the larger set of gears), and the 5th gear itself.  The 5th gear is the small gear located adjacent to the synchronizer - not much to it, huh?
3. Remove the clutch pushrod and throw-out bearing.  
4. Remove the back-up light switch.
5. Remove the gear selector shaft retaining screw (whuzzat?).  To locate this part, look at where the gear selector attaches to to the transmission.  The cylindrical hump on top of the transmission where the selector shaft resides is the selector shaft housing.  On top of it is a gadget that looks like a pop-off valve - that's the retaining screw (it is sometimes called the 5th gear detent plunger).
6. Remove the gear selector shaft end cap.  This is the large hex cap with a VW logo inside it, and is located on the front of the transmission just below where the clutch cable feeds through the transmission bracket.  Once off, a large spring should pop out.
7. Remove the gear selector shaft and spring.
8. Look up inside the gear selector shaft tube.  You will see two shift forks.  Press the one at the 5th gear side of the transmission down.  This will engage both reverse and 5th gears, and will prevent the main shaft from rotating.
9. Using a 12mm socket, remove the bolt that holds the 5th gear synchronizer to the main shaft.  It will be on there very tight, since it should have thread locking compound on it, and is torqued down pretty good.
10. The 5th gear synchronizer fork that wraps around the 5th gear selector tube will have a "locking tab" on top of it and around the selector tube.  Pry it up so the 5th gear selector tube can rotate.  Note that some transmissions will have a sleeve over the tube, rather than a locking tab.
11. Using the special tool supplied with the kit, unscrew the 5th gear selector tube.
12. Pull off the 5th gear sychronizer.
13. Remove the circlip on top of the 5th gear, pull of the thrust washer.  5th gear should come off now, but you may need a puller.
14. Set the new gear in place, with the groove on the gear face up.  The gear may require some heating for it to fit.  Replace the thrust washer and circlip.
15. Install the synchronizer back on the main shaft, with the fork back in place on the 5th gear selector tube.
16. Using the special tool once again, tighten the 5th gear selector tube until the ridge on the tube projects up over the top of the synchronizer fork by 5mm.
17. Put thread locking compound on the new synchronizer bolt and tighten it down to 111 foot-pounds.
18. Remember that shift fork in the gear selector shaft you pushed down earlier?  Push it back up.
19. Repace the gear selecter shaft, spring, and cover.
20. Stick something 12mm thick underneath the 5th gear synchronizer fork, between the transmission case and the forks themselves.
21. Press the locking plate back down on the 5th gear synchronizer fork.
22. Re-install the clutch pushrod and a NEW throw-out bearing.
23. Replace the end cover on the transmission and torque the bolts to 18 foot-pounds.

This should give you a good idea of what's involved in the conversion.  Typical shade-tree mechanic time is about 2 days.