Transmission Shift Kit Basics

Briefly, the shift kit upgrade simply alters the flow of fluid through the valve body, creating firmer shifts and improved efficiency. If it is an improvement, why didn’t the factory do it initially? That is easy. The general public would probably have been returning cars left and right, feeling that they would rather have smooth shifts, not firm. In general, the popular opinion is that shifts need to be smooth. Total performance was not at the forefront of the mind of car builders, but customer comfort was.

What Is a Shift Kit?

A shift kit is a collection of components for a vehicle automatic transmission with the goal of making the vehicle’s shifting between gears more efficient. Automatic and manual transmissions are both addressed by kits.

Many individuals are familiar with the words, but few people truly comprehend what a shift kit is and why it is needed. Briefly, the automatic transmission shift kit essentially improves upon the transmission’s shift timing which, in turn, improves the transmission’s firmness and component durability.

Automobile engineers have been known to excessively enable shift overlap in order to improve shifting smoothness. In this scenario, the transmission is operating in more than one gear at the same time. The term “slush box” was coined to describe early automatic transmissions because of their excessively smooth, disconnected feel.

The extended shift overlap improves the smoothness of the transmission, but it also puts the friction surfaces to work harder and reduces efficiency and durability. The friction causes greater heat, which destroys seals and clutches and causes them to wear prematurely.

One of the causes for short throws is a lack of traction, which may be improved with transmission shift kit. Shift kits let you use that inactivity energy for forwarding movement by better utilizing the heat normally produced by slipping during long overlap, resulting in quicker shifts and improved city fuel efficiency.

What Does a Shift Kit Do?

Numerous types of shift kits are available, each with its own set of functions. A performance-oriented shift kit is intended to improve shifts by altering the flow of transmission fluid through the valve body, although other modifications may be made as well. The more consistent each shift is, the greater the performance boost. Even if it is just fractions of a second, the faster reaction time of a shift is beneficial to your performance.

Installing a shift kit might also aid in the longevity of your vehicle’s transmission. One of the primary causes of slippage and shift overlap in the transmission is to eliminate them by reducing slip and shift overlaps. The installation of the shift kit does require transmission pan removal, valve body separation, and hole(s) drilling in the valve body separator plate. However, this is something you can do yourself at home.

Briefly, the valve body is responsible for directing the transmission fluid to various valves that operate the appropriate clutch pack or band servo. It is a tangle of fluid pathways and passageways that direct transmission fluid to push various valves that control specific components of the automatic gearbox.

We have remapped the fluid feed holes to change how much fluid is supplied to a clutch pack. By increasing the size of a particular feed hole, you reduce the application rate of the associated clutch. This gives us that quick, positive shift feels without causing the clutch slip.

Installing A Shift Kit

It is quite simple to install a shift kit. The kit will include a steel plate, some springs, and hopefully straightforward instructions from the manufacturer. The driver may use shift reprogramming kits, which are commercially available. This will consequently chirp his or her tires when they reach Second gear, which is typically the case. It is a fact of life. Everybody does it, even if the rumbling from the tires is not audible. Installing one of these kits will provide quick power transfer between gears, albeit at the cost of a smooth, continuous shift that enthusiasts will appreciate.

Unfortunately, many auto enthusiasts either live with their transmission’s seamless shifts or pay someone to modify it. It is understandable that many people are unwilling to get their hands dirty when it comes to a manual gearbox. However, regardless of what you may think, a shift kit and reorganizing a valve body only takes a few basic tools, many of which you already keep at home! This, along with spending some time in the garage or driveway. Finally, having the gearbox outside of the truck or having it on a lift would have made the process go more smoothly.

Types Of Shift Kits

There are several types of shift kits designed for different tasks, but, a performance-oriented shift kit is designed to provide firmer shifts by changing the flow of transmission fluid through the valve body. By “firming up” each shift, a performance gain is achieved. Even if it is fractions of a second, the quicker response time of a shift is a performance upgrade.

If the front servo assembly falls out (arrow) after you remove the valve body bolts, put it back in place and use a little grease to hold it. I even went to a local transmission shop and got a new O-ring for the assembly since it fell out.

In some shift kits there are options for a Heavy-Duty or a Street/Strip option to choose from. This means that a decision needed to be made. The choice between the two is application dependent. If you are installing our Shift Improver kit in a motorhome, a vehicle that is used for towing, or one that sees a lot of stop and go driving, the Heavy-Duty setup will probably be the best fit. The Heavy-Duty kit will give you firm, positive shifts, but it still delivers shifts that are comfortable enough for daily-driven street vehicles. The Street/Strip setup is the way to go if you are installing this kit in a high-performance application. Whether it is an on or off-road race vehicle or street machine, the Street/Strip setup will provide quicker, even harder shifts than a Heavy Duty install.

Other Shift Kit Considerations

The converter size and stall should also be taken into consideration when choosing between the two. Stock size converters with mild stall speeds will feel the shifts more than say a 10-inch, 3,000 stall converter using feed holes larger than 1/8-inch. Small diameter, higher stall converters will soften the shift feel.

Installing a shift kit can also help your transmission last longer. This happens by reducing the slippage and shift overlap that is inherently built into a transmission to create those smooth shifts. Installing the shift kit does require transmission pan removal, separation of the valve body, and the drilling of hole(s) in the valve body separator plate, but this is something you can do at home.

Finally

The transmission valve body is like the nerve center of the automatic transmission. It is a maze of fluid channels and passages that direct the transmission fluid to push various valves that operate the appropriate clutch pack or band servo. But, how does drilling a hole or two in a sheet of metal change the transmission’s shift characteristics? The fluid feed holes regulate the amount of fluid that is supplied to a clutch pack. By increasing the size of a given feed hole, you shorten the apply rate of the corresponding clutch. This gives us the quick, positive shift feel to prevent clutch slip which is all part of the reason for adding a shift kit to your transmission.