Re: [TR] use of overdrive

[Dave1massey@cs.com]

In a message dated 8/24/2010 8:25:52 PM Central Daylight Time, 
nafzigerg@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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