Buick Switch Pitch Converter/Trans...

Can you guy's familiar with these give me some basic facts...

...the converter works normally until you hit the lock up switch? What's the idea behind locking up the converter?

...is it electrically activated?...by a solonoid?

...is just the converter different, or the trans too?

...is it possible to disable the lock up, and let the converter spin like a regular converter all the time, or will it hurt the trans?

...what cars were the lock up feature available in, and is the switch obviously marked on the dash?

Thanks.

 

It just another name for a lockup converter. I think they dropped the name switch pitch by the late '60s. Don't hold me to that, I'm not looking at the book.
You have to have the right valve body and solonoid to go with it. You can hook it up on a toggle switch, but they were intended to be automatic, and usually hooked to either a switch on your throttle linkage or a vacuum operated switch.
The idea is that the converter locks up and then your RPMs drop a little.

 

Actually, there's a big difference between the Buick "Switch Pitch" and a lockup converter.

The Switch Pitch offered two different settings which altered the angle of the fins inside the converter and changed the stall speed. One was for economy, the other for performance. This was actually a really cool deal but was expensive and not in high demand from the public, so it was dropped. Hot rodders actually embraced it for awhile, so while racing, the stall speed could be increased for a more violent launch, but street driving would be mellow with the switch in the econo mode.

A lockup converter actually has a clutch inside of it. Typical torque converters in automatic transmissions never completely lock up. There's always a few percentage points of loss since it's actually a hydraulic joint. All the power must be transmitted through a fluid, which guarantees a loss of efficiency. To combat this, torque converters were enngineered to lock up, like clutches, and guarantee full transmission of power from the engine's crankshaft to the transmission's input shaft. This is called a "TCC" or torque converter clutch, and is engaged hydraulically from inside the transmission. In the "stock" configuration, it locks up under high vacuum conditions only when the transmission is in overdrive. So when you're on the highway, the converter will lock and offer greater fuel economy.

There are dash-mounted switches available to transfer control of the TCC to the driver, and many have learned the benefit of locking up the converter earlier. Less power loss through the converter means more power to the transmission. It's harder on all the components, especially the TCC itself, but if max performance is your goal, it's a good move. The installations I've seen have the driver hitting the lockup switch about halfway through first gear, and not disconnecting the clutch until they're decelerating - much like a traditional clutch.

The switch-pitch and the lockup TCC converters are both good in their respective roles, but they are not the same thing. The Switch Pitch is still available for Turbo 350 and 400 transmissions through Kenne-Bell Performance in Rancho Cucamonga, CA. Various lockup converters for later O/D automatics are offered through TCI, B&M, and others...most of whom also offer the dash-mounted lockup switches I mentioned.

I hope this helps out...

Scotch~!

 

First off, you should know that the ST400 (the******* your referring to) used in the nailhead buicks from 64-66 didn't have the variable pitch option in 64.

From what I understand, one of the ideas behind the variable pitch convertor was that switching into a higher stall speed when the car was sitting at a light would prevent the car from trying to "creep" forward due to the high torque factor of the nailheads.

And I don't think they used any kind of dash mounted "switch" (although one could easily install one). Basically there's a detent switch that is attached to the throttle linkage that wires in to the*******. A lot of guys who don't want to hassle with the stock equipment just wire it to the brake light switch so it switches to the higher stall speed whenever the brakes are applied.

As far as which cars they came in (and I could be wrong about this), I think any car with a nailhead from 64-66 had an st400 behind it (unless it was a 4 speed manual GS car).

Here's a link to the guy who built the ST400 in my riv.

http://www.paeenterprises.com/

 

The unique parts are the convertor, and the pump. There is also an orfice that has to be pressed into an oil passage, and a ewo prong plug for the electric kickdown, and switch pitch to be hooked up at the same time.

There was also a ST300, Buicks version of a glide, that also came with a switch pitch convertor.This was a smaller convertor, and will interchange with the one from a ST400.

When I had one in my racecar, it was hooked to a switch on the shifter. Hold the*****on, high stall, let it go, low stall. It would shock the tires pretty good. This was behind a 455 Buick.

 

the input shaft is different too. A sealing ring on the shaft near the drum

I still have parts sitting on the shelf.

The solenoid on the back of the stator support is difficult to find if you need one. Although mayb someone has found a good replacement solenoid by now.

Cadillac & Olds had the switch pitch******* too. The T-425 FWD used it for a few years too.

 

Does anyone know how to wire these things up? I transplanted one from a '66 into my '62, along with all the switches, etc. I wired it up just as it was in the '66, but it's obviously not working correctly, as I'm turning about 3200 rpm at 60 mph, and getting about 8-10 mpg. Also my kickdown doesn't work. Any tips on how to determine if the problem is in the switches or in the trans itself? Here's how mine is wired...