FYI. More subject info from the Toro mailinglist.
Paul Bartz
Date: Tue, 8 Jun 1999 09:22:45 -0500 (CDT)
From: bcroe (Bruce C Roe)
Subject: [Toro] Cost
The switch pitch feature was dropped because of cost. About all it did for
normal driving was slightly increase mileage, by allowing a smaller engine
to provide the same performance, and by locking up a little tighter than a
"compromise" torque converter.
In 1968 Olds apparently decided it was cheaper to bore the engines bigger
than to make a switch pitch, not a good way to help mileage. I was
designing electronic circuits in 1966, and the technology was there to build
a really good switch pitch control that would enhance all driving modes, for
a lot less than the cost of a radio. I always wondered if their development
team used one. Instead the cost cutters gave us a microswitch, one step
away from dropping the feature altogether. The whole TH400 design must have
been a great source of aggravation to the GM bean counters. Over designed
to the extreme (by their estimation, not mine), how can they sell new cars
when the old ones refuse to wear out and break down? They did try to
substitute some plastic and otherwise "cost reduced" parts over the years,
all of which I have found broken in junkyard units. Fortunately again for
us the "good" parts will directly swap in.
A computer controlled overdrive version (4L80E) has been serving in big
block trucks since the early '90s, and perhaps one day will show up in my
cars. Before the TH400, transmissions were the weak link at my house.
TH200, 350, 125, slim jim, power glide, 4 speed manual (German, the worst!),
I broke them all. The TH325 (79 Toro) has held up surprisingly well (must
be the shift kit), but once I get the TH425 in I can stop pampering it.
One thing I do not understand is all the transmissions GM built with a
throttle linkage cable and no vacuum modulator. A trans needs to control
shift RPM and harshness based on engine torque. Torque directly relates to
manifold absolute pressure (vacuum) which is sensed by the vac modulator.
Torque can vary over a very wide range for a given part throttle setting,
depending on RPM (not to mention atmospheric pressure & temp).
The slim jim in my 62 Cutlass was terrible about lugging that little "needs
to rev" 215 engine; my wife said I shifted it manually so much, it probably
had forgotten how to shift automatically. I even considered connecting a
vacuum modulator somehow to the mechanical input. Perhaps a horizontal beam
could be driven up and down on one end by the throttle, and up and down on
the other end the same distance overall by a vacuum sensor. I could connect
the trans mechanical input to the center of the beam to get equal input from
throttle and vacuum. Sliding the connection to one side or the other would
allow varying the input from all vacuum to all throttle position. Never
built it, got into TH400s instead. Bruce Roe
Paul Bartz
Date: Tue, 8 Jun 1999 09:22:45 -0500 (CDT)
From: bcroe (Bruce C Roe)
Subject: [Toro] Cost
The switch pitch feature was dropped because of cost. About all it did for
normal driving was slightly increase mileage, by allowing a smaller engine
to provide the same performance, and by locking up a little tighter than a
"compromise" torque converter.
In 1968 Olds apparently decided it was cheaper to bore the engines bigger
than to make a switch pitch, not a good way to help mileage. I was
designing electronic circuits in 1966, and the technology was there to build
a really good switch pitch control that would enhance all driving modes, for
a lot less than the cost of a radio. I always wondered if their development
team used one. Instead the cost cutters gave us a microswitch, one step
away from dropping the feature altogether. The whole TH400 design must have
been a great source of aggravation to the GM bean counters. Over designed
to the extreme (by their estimation, not mine), how can they sell new cars
when the old ones refuse to wear out and break down? They did try to
substitute some plastic and otherwise "cost reduced" parts over the years,
all of which I have found broken in junkyard units. Fortunately again for
us the "good" parts will directly swap in.
A computer controlled overdrive version (4L80E) has been serving in big
block trucks since the early '90s, and perhaps one day will show up in my
cars. Before the TH400, transmissions were the weak link at my house.
TH200, 350, 125, slim jim, power glide, 4 speed manual (German, the worst!),
I broke them all. The TH325 (79 Toro) has held up surprisingly well (must
be the shift kit), but once I get the TH425 in I can stop pampering it.
One thing I do not understand is all the transmissions GM built with a
throttle linkage cable and no vacuum modulator. A trans needs to control
shift RPM and harshness based on engine torque. Torque directly relates to
manifold absolute pressure (vacuum) which is sensed by the vac modulator.
Torque can vary over a very wide range for a given part throttle setting,
depending on RPM (not to mention atmospheric pressure & temp).
The slim jim in my 62 Cutlass was terrible about lugging that little "needs
to rev" 215 engine; my wife said I shifted it manually so much, it probably
had forgotten how to shift automatically. I even considered connecting a
vacuum modulator somehow to the mechanical input. Perhaps a horizontal beam
could be driven up and down on one end by the throttle, and up and down on
the other end the same distance overall by a vacuum sensor. I could connect
the trans mechanical input to the center of the beam to get equal input from
throttle and vacuum. Sliding the connection to one side or the other would
allow varying the input from all vacuum to all throttle position. Never
built it, got into TH400s instead. Bruce Roe
