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Switch Pitch, Advantages/Requirements?


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I have a 68 GS400 Convert. my current th400 and converter(non switch pitch) are shot. What would be the benefit of going to a switch pitch th400? Other than the trans and converter do I have to do anything else to the car to allow for this installation? Has anyone installed the Poston switch pitch th400 and converter combination? Results?

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If you install a switch pitch you will also need the electrical controls. they consist of a switch by the carb that controls both kick down and switch pitch ,and the proper trottle hook up which has a micro switch to shift the convertor to high stall at idle. This is to control creeping at idle.

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Other than the electrical items to change the stator angle in the converter, the Switch Pitch requires a particular converter and front pump set. It all bolts into a regular Turbo 400. <P>When the carb is at idle, the converter stator moves to what might be considered a "higher stall speed" angle to reduce creep in gear. As the carb moves from idle to cruise, the converter stator moves to a "lower stall speed" angle to be "tighter" for cruise conditions. I beleive the torque multiplication factors were 2.6 in high stall and 2.2 or 2.0 in the normal position (as a non-switch pitch converter would be all of the time). There was also a switch for kickdown/WOT that put the converter in the more performance oriented "high stall" mode.<P>Initially, the Buick advertising mentioned the extra performance from the switch pitch feature. When they got away from it in later years, the advertising mentioned "reduced operating temperature" among other things. Could have also been a production cost issue too.<P>Other than toggle switches and such, you could probably use some of the later lockup converter brake and vacuum switches to do the same things as the earlier switches did on the carb linkage. For example, use the appropriate brake switch to put the converter in "high stall" at the lights and also used one of the low vacuum switches (used to unlock the lockup converter under loaded, lower vacuum levels) to also put it into "high stall" when you throttle into it. The part numbers for the respective vacuum switches are in the back of the TurboHydramatic 350 book by Ron Sessions and HP Books.<P>The Switch Pitch is a neat idea that many non-Buick people used in the middle 1960s for an additional, incognito, performance edge on the street and at the strip too. They also came on most Oldsmobiles back then too.<P>Just some thoughts on this issue.<P>Enjoy!<BR>NTX5467

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Thanks for the info guys. After having reviewed the extra requirements/cost for switch pitch I'm going to stick with a standard th400. Perhaps at a later date go with a gear vendors under/overdrive for the performance/milage gains and still be able to maintain my stock shifter and console.

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