091-1 Transmission Problems
The Volkswagen 091-1 series transmission used in water cooled Vanagons is prone to develop problems shifting in and out of 3rd and/or 4th gear. This is caused by a poorly designed hub which is shared by both 3rd and 4th gear.
Note: Click on thumbnails for expanded images!
To the left is a picture of the 3rd/4th gear hub and the operating sleeve that rides over it. These parts are from a 1987 Vanagon GL that I used to own.
Here's a picture of the hub, without the surrounding operating sleeve. The problem is that over time, stress will crack the hub between the corners of the squared shaped cutouts in the hub. If you look closely at this hub, you can see the crack between the 2 lower cutouts.
This is what eventually happens to the cracked hub. The hub fractures, and now the operating sleeve cannot move easily over the outer surface of the hub. The driver may experience a variety of symtoms such as difficulty shifting in or out of 3rd or 4th gear; being unable to engage 3rd or 4th gear, while 1st and 2nd work fine; or being stuck in either 3rd or 4th gear, and unable to shift out of gear. Of course, look for the easy stuff first. Make sure the shifter and linkage are working fine before ripping out your transmission!
Once the failure has occurred, the only fix is to remove the transmission, and replace both the hub and the operating sleeve. which are sold together as a set. To access these parts, complete disassembly is needed. I did the work myself, but I cannot recommend that a novice mechanic tackle this job, as several specialized tools are needed. The only good news is that the replacement parts have been redesigned. The cutouts on the hub are now radiused, to prevent future stress cracking. I have not heard of any incidents of the new parts failing.
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Tom Carrington
Here's a picture of the hub, without the surrounding operating sleeve. The problem is that over time, stress will crack the hub between the corners of the squared shaped cutouts in the hub. If you look closely at this hub, you can see the crack between the 2 lower cutouts.
This is what eventually happens to the cracked hub. The hub fractures, and now the operating sleeve cannot move easily over the outer surface of the hub. The driver may experience a variety of symtoms such as difficulty shifting in or out of 3rd or 4th gear; being unable to engage 3rd or 4th gear, while 1st and 2nd work fine; or being stuck in either 3rd or 4th gear, and unable to shift out of gear. Of course, look for the easy stuff first. Make sure the shifter and linkage are working fine before ripping out your transmission!
Once the failure has occurred, the only fix is to remove the transmission, and replace both the hub and the operating sleeve. which are sold together as a set. To access these parts, complete disassembly is needed. I did the work myself, but I cannot recommend that a novice mechanic tackle this job, as several specialized tools are needed. The only good news is that the replacement parts have been redesigned. The cutouts on the hub are now radiused, to prevent future stress cracking. I have not heard of any incidents of the new parts failing.