71 Buick GS
71 Buick GS A good friend of mine says he had a '71 Buick GS with a "switch stall" cnverter in it. He said that he could push a button and would it change the stall. I told him I wasnt sure that his statement was in fact true and that I would ask you guys. Ever heard of that set up? Let me know, we got a case of Corona's on it!!
Chad
Chad
TECH Resident
Joined: May 2006
Posts: 969
Likes: 119
In 1965-1967 Gm offered in some models TH400 & TH300 transmissions a "switch pitch" torque converter. From the factory they all went to high stall at WOT, and did not go to low stall untill you released the throttle. If you wanted one of these units you could make it a high stall or a low stall torque converter, just install an on/off switch going to the open/closed stator switch on the transmission. The way to go was to use the 12" TC from the TH300 on the TH400. You could have the 12" TC reworked to give you 3,400 to 3,800 rpm high stall, and a 1,700 to 1,900 rpm low stall. Worked very well on the street where you did not want a high STR coming off the line with street tires.
I had one of these off a '68 Wildcat for my Skylark project.
The GS guys like 'em because one of their deals is, "go fast
with class" meaning comfort.
The switch-pitch ST400 wasn't around long. Supposedly you
can turn any TH400 into compatible by drilling carefully a
passage-hole to pick up hydraulic oil.
The thing was controlled with a "gizmo" attached to the throttle
linkage. From what I could see it was closed circuit at idle (so
unload the motor onto high stall), open at part throttle (for
near-lockup economy) and closed again at WOT (for performance).
But I might have that backwards, it's been decades.
Thing about the ST400 converter is, it is one -heavy- bitch. Real
heavy. I guess from extra moving parts or something.
The GS guys like 'em because one of their deals is, "go fast
with class" meaning comfort.
The switch-pitch ST400 wasn't around long. Supposedly you
can turn any TH400 into compatible by drilling carefully a
passage-hole to pick up hydraulic oil.
The thing was controlled with a "gizmo" attached to the throttle
linkage. From what I could see it was closed circuit at idle (so
unload the motor onto high stall), open at part throttle (for
near-lockup economy) and closed again at WOT (for performance).
But I might have that backwards, it's been decades.
Thing about the ST400 converter is, it is one -heavy- bitch. Real
heavy. I guess from extra moving parts or something.
Originally Posted by PBA
In 1965-1967 Gm offered in some models TH400 & TH300 transmissions a "switch pitch" torque converter. From the factory they all went to high stall at WOT, and did not go to low stall untill you released the throttle. If you wanted one of these units you could make it a high stall or a low stall torque converter, just by using an on/off switch going to the open/closed stator switch on the transmission. The way to go was to use the 12" TC from the TH300 on the TH400. You could have the 12" TC reworked to give you 3,400 to 3,800 rpm high stall, and a 1,700 to 1,900 rpm low stall. Worked very well on the street where you did not want a high STR coming off the line with street tires.
http://www.buickperformance.com/switchpitch.htm
and then this from www.trishieldperformance.com
and then this from www.trishieldperformance.com
A few words on the Variable Pitch option.
This is often know as a "switch pitch", which is a term that was popularized by Kenne-Bell, back in the seventies. GM engineers called it a "Variable" pitch, as the origin of the name relates to the "variable" angle of the torque converter's stator blades. This transmission is preferred for street cars, that see the drag strip once or twice a year. Mainly drag raced vehicles, will benefit from the proper fixed pitch converter, over a VP unit. This is fact that was proved many years ago, regardless of the "hype" you might hear. If you think otherwise, then how can this question be answered: IF a VP trans was the "Ultimate trans for a race car" then why did none of the major manufacturers reproduce it?? Surely, with the millions of TH400's in use, by enthusiasts and racers, they could have realized a tremendous profit, regardless of the investment it would require.
There are two reasons for this:
Consistency- Regardless of what type of control system is used, the converter's stator return, from high to low stall, is rather time inconsistent. That's not good, if your trying to "run the number".
Converter weight- 11,12, and 13" converters are heavy. A good 8, 9 or 10" converter is considerably lighter, which allows the engine it rev faster, which in turn, makes the car faster. Simple as that.
That being said, don't get us wrong. We love the VP setup for a street car. So much so, we developed the only furnace brazed, high quality torque converters on the market now. It adds a "neat" dimension to your project, and allows the advantages of a higher stall converter, without the excessive heat buildup, and slippage. IT is used for just that in some of the cars we do here. Not because we would encourage you to build a car, with cam timing that REQUIRES it. Even our Level 2 engine can be driven around in low stall, in traffic, with no fear of stalling, once everything is warmed up and "normalized".
This is often know as a "switch pitch", which is a term that was popularized by Kenne-Bell, back in the seventies. GM engineers called it a "Variable" pitch, as the origin of the name relates to the "variable" angle of the torque converter's stator blades. This transmission is preferred for street cars, that see the drag strip once or twice a year. Mainly drag raced vehicles, will benefit from the proper fixed pitch converter, over a VP unit. This is fact that was proved many years ago, regardless of the "hype" you might hear. If you think otherwise, then how can this question be answered: IF a VP trans was the "Ultimate trans for a race car" then why did none of the major manufacturers reproduce it?? Surely, with the millions of TH400's in use, by enthusiasts and racers, they could have realized a tremendous profit, regardless of the investment it would require.
There are two reasons for this:
Consistency- Regardless of what type of control system is used, the converter's stator return, from high to low stall, is rather time inconsistent. That's not good, if your trying to "run the number".
Converter weight- 11,12, and 13" converters are heavy. A good 8, 9 or 10" converter is considerably lighter, which allows the engine it rev faster, which in turn, makes the car faster. Simple as that.
That being said, don't get us wrong. We love the VP setup for a street car. So much so, we developed the only furnace brazed, high quality torque converters on the market now. It adds a "neat" dimension to your project, and allows the advantages of a higher stall converter, without the excessive heat buildup, and slippage. IT is used for just that in some of the cars we do here. Not because we would encourage you to build a car, with cam timing that REQUIRES it. Even our Level 2 engine can be driven around in low stall, in traffic, with no fear of stalling, once everything is warmed up and "normalized".
