[TR] use of overdrive
Dave1massey at cs.com
Dave1massey at cs.com
Wed Aug 25 11:53:57 MDT 2010
In a message dated 8/24/2010 8:25:52 PM Central Daylight Time,
nafzigerg at yahoo.com writes:
> I've never had an overdrive such as the A-type in a car before (tr-6). I
> love
> it but am curious about it's use. It works very well within a gear range.
> But
> is there a way to quickly shift from 2nd overdrive into 3rd regular
> (underdrive)? Then on through the gears giving a person 7 gears? LOL or
> not.......i've been afraid to experiment and don't really need it but just
>
> curious.
>
As has been mentioned you could just switch to OD off whilst shifting. I
have found that if the sequence is just right you can trick out the synchros
and get gear clash. To avoid this I would recommend that you switch other
OD off just as you depress the clutch and then pause half a second before
selecting the next gear.
But as also has been mentioned, skip the whole thing since the difference
is so negligible.
I prefer the J-type just for the reason of drive line shock. Since the
J-type has no accumulator it will engage the OD more slowly. When I drive the
A-type I depress the clutch partially to minimize the driveline shock.
Some shift harder than others. I suspect it may have to do with the
adjustment of the valve. If the solenoid only opens the valve slightly the
engagement will occur more slowly than if the valve is opened more widely. Since
the book procedure usually doesn't work most folks (myself included) adjust
the solenoid clamp to open the valve quite wide. Making minor adjustments
(a big PITA, BTW) may soften up the OD engagement.
Or you could do what they did in the Austin Healey application. The Healey
3000 has a very big motor with a very heavy flywheel. The OD's on these
cars were fitted with a sleeve and smaller piston and spring in the
accumulator reducing the capacity of the accumulator. This means the pressure drop
upon engagement is much more pronounced meaning that there is less pressure
applied at the point of clutch engagement resulting in a softer shift (less
jerk). I have fitted these parts to my TR3 OD and when I get it on the road I
will report on the success (or lack thereof) of this attempt.
Dave
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