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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 >


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