There is probably a transmission shop in almost every area in the country that can rebuild and modify transmission for American made vehicles. Whether it is a newer Camaro or a 60's Mustang, there are plenty of aftermarket components and decades of technology available for the average transmission mechanic to utilize.
This cannot be said for Volkswagen's 01M automatic transmissions found in Jetta, Bettle, Passat and other VW vehicles. In factory form, these transmissions demonstrate several problem areas that can cause failure in as little as 30,000 miles with a stock engine and much sooner in modified applications.
Anemic mass produced factory components, lack-luster shift quality and incorrectly configured torque converters plague the 01M automatic transmission equipped vehicle. This is in conjunction with the automatic's unpleasant tendency to burn out the "B-2" and "K-3" clutches in protest of even moderate increases in engine output.
Topping the list of internal modifications is the need to address the issue of valve body calibration. The valve body mods are really the foundation of any performance trans rebuild- whatever the vehicle.
An automatic transmission utilizes a network of orifices, valves, accumulators, electronic actuators or solenoids, and passages that control and route hydraulic pressure to the appropriate places to apply the clutches and bands.
One of the problems with the 01M is that the valve bodies tend to wear out. This is the result of the valves oscillating in their respective bores over millions of cycles during the life of the transmission. This means that before any modifications to the valve body are even contemplated, the valves and bores that the live in must be reconditioned to "tighter than new" tolerances.
The 01M valve body needs to have several of its bores machined and have oversize valves installed to restore hydraulic integrity.
Without going into elaborate detail which would fall outside the scope of this article, suffice it to say that modifying the valve body effectively changes the rate of clutch apply and also increases the clamping force with which these components have to work with. This is why shift kits and modified valve bodies produce that firm, performance type shift that increases the transmission's overall capacity for power handling.
Further inside of the unit, all critical support bushings need to be replaced to insure that the centerline of the transmission runs in perfect alignment with the centerline of the crankshaft. Ignoring this step puts lots of undue stress on the internal transmission components. Visualize two meshing gears trying to run on different centers- not something that is going to last too long, never mind transfer power efficiently.
To be up to the task, many of the other parts also such as the pinion shaft, the front differential ring gear and the planetary gearset must undergo various metallurgical processes. Included in this is heat treating, Meta-Lax stress relieving, and cryogenic treatment (freezing them in liquid nitrogen at -300 degrees Fahrenheit to 'reset' the part's structure on the molecular level).
Next, all of the required seals and gaskets are changed to materials that are better able to cope with the heat and stress that is common in high powered applications.
Lastly, performance clutches and steel reaction plates are installed and their clearances set to much more exacting specifications than those that are used by the factory. Most importantly, IPT utilizes a proprietary 7 friction disk "B-2" clutch pack and a 7 friction disk "K-3" clutch pack which increases the second, third, and fourth gear torque capacity by over 35% versus the factory set up- this is the key to getting a high powered vehicle make a 1-2, 2-3, and 3-4 shift instead of just bouncing off the rev limiter.
As for the modifications outside of the gearbox, the next thing of importance is of course the torque converter. In an automatic equipped vehicle, one of the most important components in the entire car in regards to optimizing performance is a correctly configured converter.
In addition to being made with many strength improvements over the factory piece, a performance converter enables a vehicle to better take advantage of the RPM range at which power is made.
In essence, a torque converter is an infinitely variable transmission in and of itself, and altering its torque multiplying characteristics becomes absolutely necessary when other variables in the vehicle are changed (more boost, power enhancers, etc).
On a diesel powered vehicle, the correct torque converter configuration is quite different than that which would benefit a gasoline powered car. In short, diesels make much more torque without the increase of RPM's and shift in power band that a gas motor needs to increase horsepower.
Lowering the stall speed and increasing the efficiency of the fluidic coupling effect are the name of the game in a diesel. This can often be seen on a dyno with more of the power making its way to the wheels.
Even in otherwise stock VW vehicles, ET reductions of up to full second are not at all uncommon with the addition of a properly configured converter.
Transmission, torque converter and valve body upgrades are not only for American made vehicles anymore. Increased performance, durability and more efficient shifting is now available for the vehicles of almost every manufacturer- thanks in part to the few companies that are willing to do the research and development work required for this rapidly growing segment of the automotive aftermarket.
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