The Shift Kit Explained
by Burt Brown Racing Transmissions 2005

There are several forms of shift kits. An aftermarket shift plate is a seperator plate which goes between the valve body halfs that has been modified by eliminating and enlarging holes that feeds the transmission clutch and band apply circuts.

Transmission builders such as myself can do this with a drill and a few drill bits with the stock plate. However I recommend the aftermarket shift improvers and shift kits that come with springs, parts and pieces. A larger feed hole firms up the shifts by increasing fluid feed volume to clutch or band apply, a smaller feed hole softens the shift by slowing down the fluid feed volume to clutch or band apply.

Overlap can be best explained by giving an example. If you ride your car brakes, the pads will fail sooner and generate heat, this is somewhat like overlap. Overlap in a transmission is when an upshift takes place to the next higher gear but the lower gear has not fully released all the way yet so for a short time the transmission is in two gears at once for a short time before the upshift is completed. This is taking place in all the upshifts everytime you take off from a dead stop. This generates heat and removes clutch and band lining at a greater rate. It also glazes/polishes the clutches, steels, drums and bands.

A shift improver is recommended for your every driving and adds quality to a stock rebuild to add longer life to your transmission.

A high performance/race shift kit will really wake up that slush box. When you install a high performance/race shift kit this changes the shift quality, feel and to some degree and you will loose comfort. This type of shift kit increases the volume and pressure to the clutch or band feed apply circut. This will tranform your transmissions shifts into hard, tire chirping shifts during upshifts.

This kit usully comes with instructions, seperator plate, gaskets, a big spring selection and drill bits. This type of shift kit is for those street, strip setups where loosing comfort is not an issue. When you install a competetion shift kit, you will really make those 4 speeders jealous with those chirping tires and with no clutching between shifts! Burt Brown
Transmission Repair
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  There are shift improvers that give you instructions, replacement springs to modify the valve body and drill bits to modify the valve bodystock seperator plate, this recalibrates the transmission to work better then stock by correcting drag and overlap timing between shifts this also reduces heat.
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