Date: Wed, 1 Dec 1999 08:00:24 -0500
Reply-To: eric.henning@US.ABB.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Eric Henning <eric.henning@US.ABB.COM>
Subject: Re: vanagon Digest - 30 Nov 1999 - Special issue
Content-type: text/plain; charset=us-ascii
Tony: the reference to the length of cable is mysterious. I don't even
remember how I interpreted it, and the manual is not clear, but I do
remember that, as you say, a slight adjustment makes a great difference in
performance. As the thunk disappeared, the shift points got lower. The car
gets into 3rd gear much more quickly now. I am presuming that indicates
lower, not higher line pressure, but I am still a bit baffled. I only know
that this adjustment works to cure the "thunk", and at the same time cures
what I found to be excessively slow shifts (on an original, not rebuilt BW66
that is thriving, apparently, on Dexron III, at 100,000 miles = 160,000 km).
Gregory
- ----- Original Message -----
From: DTG-PWARNER <pwarner@ArkansasUSA.com>
To: <xj@jag-lovers.org>
Sent: Tuesday, November 30, 1999 10:42 AM
Subject: [xj] Re:transmission thunk
> Tony Gardner wrote:
>
> > According to page 44-33 of the manual "increasing the length of the
cable
> > increases pressure". I have always taken this to mean increasing the
gap
> > between the ferrule and the end of the outer sheathing of the cable (Gap
> > "A" in the manual). Therefore, because a stretched cable increases "Gap
> > A", does this result in increased pressure and, is this the underlying
> > cause of transmission "thunk"?
> > But, the throttle, as it opens, increases pressure by pulling on the
cable,
> > therefore intuition suggests a stretched cable would in fact decrease
> > pressure?
> > On my car, the transmission pressures are above spec even with "gap A"
set
> > to zero and I still have thunk. Do I move the ferrule?
> >
> >
> I would interpret the statement "increasing the length of the cable
increases
> pressure" to mean 'increasing the length of the inner cable showing at the
> engine compartment end', which also means the end of the inner cable
inside the
> transmission would be moved farther as the inner cable is pulled from the
outer
> cable by the adjustment and by action of the throttle.
>
> I mistakenly induced the dreaded thunk in my 85 Sov 4.2 awhile back when I
> increased the amount of inner cable showing. (I had just improved the
shifting
> on our TH700R4 equipped 87XJ6 by doing this same thing and thought it
would make
> the Sov more aggressive also.)
>
> I got rid of the thunk in the Sov by decreasing the length inner cable
showing
> to the point that the 'ferrule', a bit of metal crimped onto the inner
cable,
> was right at the threaded end of the outer cable; the upshift points were
not
> drastically changed on the Sov by this adjustment either way, but the 2 to
1
> downshift certainly was.
>
> It takes so little force to move the inner cable that I can't imagine it
> stretching much over time, but if it did I'd expect the transmission
pressure
> and the shift points to be lower for a given throttle position, not
higher.
>
> You may have something else going on inside the trans, but to reduce the
thunk
> with cable adjustment alone you'd have to reduce the amount the inner
cable is
> being pulled at low throttle settings; I.E. reduce the length of inner
cable
> showing in the engine compartment, and you may have to move the 'ferrule'
to do
> that.
>
> Note that other listers (Dr. Gregory?) have reported that not all TV
cables have
> the 'ferrule' and they've adjusted theirs by extending the outer cable end
a bit
> at a time until the thunk just goes away.
>
> Good luck, Tony
>
|