April 28, 2017
Do not drill feed holes too large.
|Original Orifice Dia.||Enlarged Dia.|
|+ 10% area||+ 20% area||+ 30% area||+ 40% area||+ 50% area|
|Common Fractions and Decimal Equivalents|
Drilling clutch feed orifices is a proven way to reduce clutch engagement time and firm-up shift feel. This helps with otherwise lazy-shifting transmissions, hardworking commercial applications or units modified for performance use. But many times when a feed orifice is enlarged, the hole is drilled too large and the change in shift feel is far greater than intended. This results in harsh shifts, which many customers do not like and view as a nuisance.
If you wish to enlarge feed orifices, these guidelines will help you determine what drill bit size corresponds with a specific percentage increase in orifice area so you are less likely to cause problems when making these common modifications. Experience has shown a 20% increase yields a subtle yet noticeable change in shift feel without causing harsh shifts that generate customer complaints.
1-2a is the feed orifice, 1-2b should always be larger than 1-2a. 2-3a (some models) is the low-speed 2-3 feed, 2-3b is the high-speed 2-3 feed. 3-4 does not have a conventional feed orifice.
There are three different plates for the 400: the '89-later seven-ball plate and two versions of the six-ball plate. The difference between the six-ball plates is the location of the 2-3 hole.
April 28, 2017
February 08, 2018
October 25, 2018
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