>
>
>> >there was a limited availability option that was supposed to drop you
>> >out of OD when you put your foot to the floor.
>> >
>==================
>> I don't think so. I have a 67 MGB with a vacuum switch correctly
>connected.
>>
>> It works as described; holding you in overdrive if you have your foot off
>
>> the gas.
>
>Ok guys, what gives? I don't have OD (yet) so I'm certainly no expert, and
>when I do find one for a 1969 it probably won't have a vacuum switch. But I
>don't get it, aren't you each saying the same thing?
>
>Larry
>1969 MGB
>
I may be wrong, but I believe we are saying totally different things. There
is a misperception about vacuum switches. Not many people have these
switches, and is seems that those without them think the way they work is as
follows:
Leave the driver's switch off, the overdrive is off.
Turn on the driver's switch, overdrive kicks in if you are not accelerating
hard, kicks out if you are accelerating hard - sort of an automatic
overdrive based on vacuum and how hard you accelerate.
Turn off the driver's switch, and it turns off the overdrive.
As I said, this is totally wrong. With the vacuum where it was designed to
go, the correct vacuum switch, and wired correctly it actually only protects
the transmission getting jolted when the overdrive is turned off. The way
it works is as follows:
Leave the driver's switch off the overdrive is off
Turn on the driver's switch, the overdrive is on.
Turn off the driver's switch, overdrive turns off IF AND ONLY IF you are
accelerating hard enough to pull less than 15 lb vacuum (it doesn't take
much). If you have your foot off the gas (the vacuum is 20-30 lb) and the
vacuum switch holds you in overdrive until you acclerate and lower the
manifold vacuum below 15 lb (and it doesn't take much). From here you are
back to leave it off it stays off, you can't just lift off the gas a little
and engage the overdrive. This is not an automatic trans type function, it
is to protect the gears and bearings.
You may think tese two scenarios are the same, but believe me you can not
have the overdrive on, accelerate hard, and have it kick to off without
manually flipping a switch. Further, if you flip the switch at just about
any throttle opening, it will disengage. The vacuum switch only acts if you
are turning off the driver's switch while having your foot off the gas (or
turn off the driver's switch, and then drop the rpms to about idle while in
gear).
I hope this clears up the difference. If you drive with one it will be
notable as to how you think it will work, and how it does work.
Phil Bates
58 MGA
67 MGB
75 Jaguar XJ12C
52 MG TD replicar (VW)
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