The following write-up is an article by Lucas Valdes (Prez & Resident Mechanical Engineer of GoWesty) explaining the inevitable failure of ALL stick-shift Vanagon transaxles produced prior to 1990. This information is based on our personal experience rebuilding countless units here in our workshop, coupled with our knowlege of stress failure analysis.
There is a part in all Vanagon stick-shift transaxles called the 3-4 synchro hub—which has a flawed design. It cracks and eventually breaks without warning, usually before 150,000 miles, sometimes as early as 70K or 80K miles (see photo). This part transfers the torque supplied by the engine from the mainshaft of the transmission to either 3rd or 4th gear. Whenever you're in 3rd or 4th gear, this part is stressed. Sometimes only one section breaks (far left photo #1) and you might keep on trucking for a while with some weird shifting symptoms, giving you enough time to get to a shop and figure things out. But if two or three sections break simultaneously (photos #2 and #3, which is what usually happens), you’re screwed. Usually the transaxle jams in neutral, 3rd, or 4th. At any rate, when this happens you ain't going nowhere.
If you look closely at the photos, you will see that the cut-outs in the updated part (photo #5) are rounded instead of squared like the original design (#4). The sharp corner of the original design causes what is referred to in engineering design lingo as a "stress riser." Over time a crack begins at this sharp corner and begins to propagate around towards the next sharp corner, eventually causing that section to break off entirely. The VW-redesigned part does not break (#5).
We don't know the exact date this redesigned part was introduced into vehicle production, but it is thought to be sometime in late 1989 (first used in 1990 year-models). Over the years, we have documented the date code on the side of each transaxle we have disassembled in an effort to determine when the change took place. So far, the earliest transaxle we have disassembled with the redesigned part already fitted is trans #ACW 09030 (read: ninth day of March, 1990). So, if your Vanagon was manufactured in 1988 or earlier, you’re in trouble. Get it replaced before it breaks. If it was manufactured in 1989, you might be okay (you gotta ask yourself, "Do you feel lucky? Well, do ya, punk?"). If it was manufactured in March of 1990 or later, you are definitely in the clear.
GoWesty rebuilt transaxles always use the redesigned hub. We have rebuilt countless transaxles, and we have never disassembled a single one with an original 3-4 hub design that did not have at least three cracks started. We ALWAYS replace this part. You might ask, "Why replace the whole transaxle? Why not replace just the bad part?" Well, the part is buried deep inside, and to replace just the bad part costs about $800 in parts, labor, and materials. GoWesty offers completely rebuilt transaxles, with the updated hub, and a 48/48 warranty—which we consider a better value than simply replacing the hub.