Close, but backwards.
The ball just below the spring and plunger (under the test plug) seats against
the case
<blocking> oil from the accumulator from entering the passage to the operating
pistons. The
small spring and plunger above the check ball don't resist the force of the
oil, rather they
work with it simply serving to ensure a positive return of the check ball to
it's seat when the
overdrive is disengaged.
When activated, the solenoid raises the operating valve forcing the check ball
off it's seat
(and against the small spring and plunger) allowing pressurized oil from the
accumulator around
the ball and entering the passages to the operating pistons. When
de-activated, the valve
drops down and the check ball seals off the oil from the accumulator. The
valve drops further
than the check ball exposing the hollow end of the valve. The force from the
cone-clutch
springs pushes back against the operating pistons forcing the oil from the
operating piston
chambers back through the exposed hollow part of the valve and out a small
drain in the bottom
of the valve back into the overdrive sump.
I agree with Randall that the o-ring accumulators seem like a better design
from a sealing
standpoint, but keep in mind that there are an awful lot of compression rings
on the earlier
version. By carefully staggering all the end gaps, you can still affect a very
good seal such
that the accumulator will hold pressure for days on end.
Tony chose not to remove his accumulator and it held from a Sunday afternoon
all day Monday to
Tuesday morning when I disconnected the gauge with just about 100 PSI still
showing. On my
rebuilds, I usually let them sit overnight after a break in run with the gauge
connected and
it's not uncommon to have them read between 350 to 400 PSI the next day. I
suspect that if
Brian had the plunger and spring installed, his readings would be very similar
to Tony's.
I also agree with Randall that its a moot point as the unit will build up
normal pressure in
the time it takes you to back out of the driveway (the pump doesn't care which
way the
mainshaft is turning) and accelerate up through first gear.
Cheers!
Brian Schlorff
Anthony Rhodes wrote:
> Randall,
> Since the ball is a pressure relief valve, I'd assume that the spring
>pressure on the ball
> is approximately that exerted by the 400+/- psi on the other side. However
>when the
> mainshaft stops spinning (and actuating the OD pump), then without the
>spring, there
> might be less pressure on the ball keeping it sealed (if the spring is
>missing), which
> would allow the accumulator to leakdown more quickly. Otherwise why have the
>spring at all?
>
> -Tony
>
> Message text written by INTERNET:owner-triumphs-digest@autox.team.net
> >From: Randall Young <randallyoung@earthlink.net>
> Subject: Re: TR4 - OD Gearbox Install
>
> I'd like to respectfully suggest that, if the ball seals at all, the
> force of the oil pressing on the ball is going to be far greater than
> the force of that little spring.
>
> Assuming the ball seat is 1/8" in diameter, 400 psi of oil would exert
> about 5 pounds of force on the ball. I haven't tried to measure the
> force of that spring, but it's surely much less.
> <
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