| [GMCnet] Switch Pitch transmission controller [message #200619] |
Mon, 04 March 2013 18:45  |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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Instead of a toggle switch, a fellow named Bruce Roe from the Chicago area makes an electronic controller for the switch pitch that reads the vacuum of the engine as well as the brake light and so the switch pitch will work on and off as needed. It also has a timer circuit to turn off the switch pitch to prevent overheating. I have used this controller for many years now and really like it It comes with a two position center off toggle switch. One position is "on all the time". The other is the automatic switch. Sometimes when going up a grade the timer will cut it out. I look at my tranny temperature gauge and if its not hot I will use the "on" or override switch position until I pass that truck or get up the grade and then switch back to the automatic position.
I know that Manny and several others use Bruce's controller.
He is a contributor to the GMCMH-EFI mailing list. His email is bcroe@juno.com
Here is some info from Bruce several years back:
> bcroe@juno.com
> >
> > The switch pitch torque converter gives you a dual
> > range in every gear. I like to think to think of them as the
> > "performance" and "economy" ranges. The performance
> > range gives a higher stall speed than a standard
> > converter, with several benefits. First, the torque
> > multiplication is about 2.5 versus standard 2, or an
> > extra 25%. Second, the engine will be able to pick up
> > about an extra 500 rpm, allowing it to get more into its
> > best power and torque range starting up. Multiply
> > both these together and you have a real advantage. I
> > use a 2.41 differential on a 4100 lb car which will
> > outperform a 2.73 standard, 0-60 is 7.5 seconds with
> > the switch pitch. Third, the shifts will be noticeably
> > smoother
> >
> > The performance range is less efficient, and for difficult
> > situations a motorhome needs a trans temperature
> > gauge to make sure you get out of the performance
> > range in a minute or so. Usually 30 seconds is all
> > you will need. Once you switch to the economy range
> > the converter will be slightly tighter than a compromise
> > design standard converter, so you will probably see
> > some improvement in gas milage. I figure 3 to 5% on
> > my cars
> >
> > At high engine speeds, all torque converters decrease
> > gradually to a 1:1 torque in to out. Since you will not be
> > using performance mode for cruising, additional torque
> > here will require different gears. The Caspro Power
> > Drive is a pretty good unit. If your trans is ready for a
> > rebuild, it solves the problem of getting a new chain and
> > sprocket set. I am using one in reverse on my car to
> > maximize economy, while a switch pitch converter gives
> > me plenty of performance. There are of course other
> > options with the final drive ratio
> >
> > The usual way to operate the switch pitch is to use
> > performance range from standstill at least into second
> > and possibly into third in a motorhome. Economy range
> > would be used after about 30 seconds. A car would be
> > set to cover all shifts in performance mode, around
> > 14 seconds
> >
> > Caspro uses a Switch Pitch trans on their own GMC
> > motor home. The electronic controller makes this
> > function automatic, instead of a toggle switch you are
> > always playing with. The same is true on my cars,
> > which are more responsive and so smooth many
> > people mention it. An override switch is used on
> > motorhomes for special situations
> >
> > I have heard quite a bit of talk about using switch pitch
> > in other motor homes, but I don't have any direct info.
> > Brent Covey did some transmission work on
> > motorhomes lately. You might ask him if any were
> > converted to switch pitch at BrentCovey@hotmail.com
> >
> > I sell a few of the switch pitch controllers to car owners
> > who already have a switch pitch trans every year. I just
> > say that if they don't think its worth the money, I will buy
> > it back. No one has ever asked for a refund. Good luck
> > on your project. Bruce Roe
> >
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