[928uk] 3 speed gear change rpm

[Ben Hodges]

Good work Todd



On Fri, 14 Jun 2024 at 23:00, todd via 928uk <928uk at lists.928.org.uk> wrote:

> Just to wrap this up (for anyone with similar issues)
>
> I adjusted the bowen tensioning bolt (side of gearbox) and the gear change
> raised to 4500. I increase pressure module one complete turn (clockwise)
> and gear change raised to 5000rpm. Im happy there. At some point I will try
> Smithy's suggestions below, but for now Im happy.
>
> I must say, for a 45yr old car that has sat dormant for 16 or so years,
> then rebuilt by a novice like me - it does accelerate pretty well. Its not
> rocket, but it certainly respectable. And the thrashing its been getting
> recently has only made it happier.
>
> Thanks all
>
> Todd.
> (had to resend for various stupid reasons 😊 )
>
> -----Original Message-----
> From: todd at oxfordeye.co.uk <todd at oxfordeye.co.uk>
> Sent: Saturday, June 8, 2024 11:19 PM
> To: smiffypr at gmail.com; 928uk at lists.928.org.uk
> Cc: todd at oxfordeye.co.uk
> Subject: RE: [928uk] 3 speed gear change rpm
>
> Solid suggestion... I'll give it a go tomorrow
>
> I have 100% confirmed the kickdown now works, that at least that 😊
>
> Thanks 😊
>
> -----Original Message-----
> From: 928uk <928uk-bounces at lists.928.org.uk> On Behalf Of Paul R Smith
> via 928uk
> Sent: Saturday, June 8, 2024 11:15 PM
> To: 928uk at lists.928.org.uk
> Subject: Re: [928uk] 3 speed gear change rpm
>
> Bear in mind that I know nothing about autos, so I am just talking theory.
> If you want the box to think you have WoT, it will have no vacuum, so
> disconnect the vacuum line to the box and block the engine side of the line.
> You want the cable to tell the box that the throttle pedal is on the
> floor, so cable tie the lever to imitate that.
> You want the kickdown solenoid powered, so run 12v to that.
>
> If it still won't go to higher revs, you then know that the problem is
> inside the box.
>
> Smiffy
>
> On 08/06/2024 23:05, todd via 928uk wrote:
> > Just to update :
> >
> >
> >
> > I adjusted the Bowden cable and lock nut(side of gearbox where Bowden
> > connects) and it's definitely tight enough (I can even tighten it
> > enough to stop throttle opening fully. I've wound it back a bit now).
> >
> >
> >
> > But, the car changes at 4500rpm max throttle.
> >
> >
> >
> > As I understand it, the gear change is based on pressure. On one side
> > you have the vacuum of the engine and on the other you have the
> > throttle position (communicated to gearbox via Bowden cable). Once
> > vacuum pressure exceeded throttle pressure the gearbox changes gear.
> > (Shout if that is
> > incorrect)
> >
> >
> >
> > So, my new question is : what else could be wrong? Low gear change
> > tells me the vacuum pressure is too high for the throttle pressure
> > (but I know the throttle is max). Is there an o-ring or something I
> > need to change to increase throttle pressure? Or a way to reduce vacuum
> pressure ?
> >
> >
> >
> > Perhaps increasing pressure modulator?
> >
> >
> >
> > Any help appreciated
> >
> >
> >
> > Todd
> >
> >
> >
>
>
>