ChrisTTiaan

The VW transmission, or any modern transmission for that matter, relies on brass syncronizer rings to allow matching of gear speed to transmission input shaft or pinion shaft speed to allow grind-free shifting. Picture in your mind that this brass syncronizer ring is a kind of brake pad acting against the gear itself which would be analogous to a brake rotor. Now each "brake pad" syncronizer has to stop it's gear from turning every time a different gear is selected. (All forward VW gears have their own syncronizer. Reverse does not have a syncronizer.) Now, when a car's driver moves the shift lever faster from gear to gear, the syncronizer ring has to stop it's gear from turning in less time than if the shift was made slower. Sometimes a gear change is made faster than what the brass syncronizer can physically handle and the gears grind together before they mesh, often causing only very slight damage to the gear teeth as the gears are extremely hard (Reverse gears are the exception here, they are soft.). So, what you see is that it is possible to overwhelm the syncronizer's ability to perform it's function as the speed of shifting is increased.

With any short shift kit it can be assumed that the time interval for all of the required "gear braking" CAN be reduced since the gears are closer together. If you select gears at the same speed as when your car had a stock shift linkage then there is no difference and your syncronizers have plenty of time to do their job. Basically what I'm saying here is that the faster you change gears even with a stock shift linkage the greater the chance for gear grinding. And so if you speed shift your gears with your new short shift kit then you run a greater chance of getting gear grind. It's that simple. It doesn't matter whose kit you are using, either. If you overwhelm the syncronizer's ability to do it's job then you will eventually get gear grinding and you will also overheat and destroy your syncronizer for the particular gear that is grinding. The only recourse in this case is to replace the brass syncronizer ring inside the transmission which is somewhat expensive. And if you grind gears for too long you might break a tooth off of one of your gears and this floating tooth is not very good for the guts of your transmission.

It is extremely important to note that if you already have a bad syncronizer for a certain gear BEFORE you install ANY short shift kit then you will only put more stress on the syncronizer and you will likely get more lovely grinding than before. I recommend that you DO NOT speed shift your transmission or install a short shift kit if you have experienced significant gear grind at any time. You will wear out your syncros or break a tooth if you do. A grind every once in a while is normal since we can't clutch and shift perfectly every time but you must realize that if you have a persistent grinding problem it will likely get worse if you shift faster. If you have to "granny shift" (wait longer to engage a gear after pushing in the clutch) your transmission to avoid grinding before installing a short shift kit then DON'T install a kit until you replace the syncronizer for the gear that is causing grind. In summary, as with guns, short shift kits don't kill transmissions, PEOPLE kill transmissions! Knowledge is power.

With all of this said, I recommend two quarts of Redline gear oils (MT-90 or MTL) for all VW transmissions since they have the best frictional properties for the brass syncronizer rings in my opinion. If you want the best for your car then change the gear oil (two quarts) and fix all leaks! Almost every VW transmission failure I have seen is from running a transmission out of gear oil from final drive oil leaks. The other leading cause of failure is by breaking off a gear tooth by letting gears grind and/or NOT replacing a worn/slipping clutch which will also increase the chances for grinding.

evan

Nifty post. I would add that speed shifting is hard on the linkage too. Don't ask how I know. :-(

Haywood Jablome

a regular shifter or shifty eyes matters not.

Its how you shift. If you abuse the gearbox you get premature syncro failure.

ChrisTTiaan

Thats exactly what it says.

CarTTman

Sorry folks: aka why a short shifter may void your transmission warranty.