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"This solenoid could have been designed so that the default condition (power off) left the OD engaged. Why it wasn't, I just do not understand..."
You aren't alone there, but I think that's a somewhat parochial view. A default OD might be good for those who (as Art Benstein puts it) "drive mainly on the plain". But consider Volvo's world-wide market and the varying terrain.
I think there are many areas where a default OD would result in feast or famine uphill drives. You'd start in OD, then bog down. So you'd floor the pedal to get kick-down 3rd gear—and also get way more RPMs than you need. Try to feather the throttle a bit and you're back in OD and soon bogging down again. And so it goes—in and out of OD, tach needle sweeping the dial.
Upstate NY has many such hills on non-freeway roads, where I find the selectable downshift a real benefit, allowing me controllable, moderate RPMs until I'm over the top. I used to try those same hills in OD, when the 940 was new to me, and found the constant drifting in and out of OD a true PITA. So I think from a global view, Volvo probably got it right.
On that same subject, I find it odd that we don't hear similar "default is bass-ackwards" complaints from the M46 OD people, since their default is also OD OFF. Here is a comparison between the AT and MT types:
• They both use a shifter switch to control a relay, which controls a solenoid.
• In both types, the solenoid is energized to engage OD.
• Both types allow OD On/Off selection by the shifter switch.
• Both types default to "No OD" with an electrical failure.
The only difference:
• In a MT car, the starting default is OD OFF until selected ON.
• in an AT car, the starting default is OD ON until selected OFF
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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