Transmission shifting

[blank]

Has anyone replaced the steel line that runs from the intake manifold down
to the vacuum modulator. It appears to be 1/8 inch steel tube and, in the
case of my coach, is in pretty bad shape.

Patrick

>

>
> think it should. As a matter of fact, unless I manually shift
> it, it will not down shift even at 40mph. Any technical
> discussion would be appreciated. Dean Hanson >>
>
> The first thing I would check is the vacuum line to the
> vacuum modulator which is located on the passenger side of the
> engine. If you have a vacuum leak it will affect the shifting.
> Make sure that the line is not cracked and leaking or loose
> from the connections. You can also check the modulator by
> trying to pull a vacuum on it. If it holds a vacuum the
> diaphragm should be OK and then you'll have to look for
> another cause.
>

 

[blank]

Dean, if you will look under your dash at the top of your accelerator linkage,
you will find the kick down swithc. There are numerous reasons that this
component stops working, First off, the linkage could be bent, as many are, and
the switch is not being moved far enoughj to activate it. Secondly, the switch
may be defective. It is very eas to test the switch, either with a volt/ohm
meter, or if you turn on the key and slide the swithch into the activated
position, you will hear a soft click from the transmissionm. This is the kick
down solonoid activating. I think if you will try this, you might find your
problem. Good luck.
Pat 77 Birch

> Fellow GMC'ers; My '73-23' does'nt shift down the way I think it should. As a
> matter of fact, unless I manually shift it, it will not down shift even at
> 40mph. Any technical discussion would be appreciated. Dean Hanson

 

[travism]

> A bit of what I learned on my 76 Birchaven:
>
> The kickdown switch is a self-adjusting device. It must be "reset"; then,
> when the accelerator is first used, the switch "sets" itself. There is a
way
> to reset the switch externally but since I didn't know about this feature,
I
> disassembled the switch to learn it and reset it while I was inside.
>
> However, resetting my switch would not have solved the problem: The
> lubricant in the switch was so deteriorated / coagulated that the contacts
> couldn't complete the circuit.
>
> It's easy to repair the switch: Carefully bend back the tabs which hold
it
> together. Take it apart cautiously, noting the positions of the various
> parts. I don't recall how many but only a few. A good cleaning and
greasing
> will make it work perfectly when reassembled. Be sure to figure out the
> "reset" position before you reassemble the switch (and how to do it
> externally, which I forgot!).
>
> Ken Henderson
> 76 X-Birchaven

It's easy to reset...just grab the protruding plastic rod and pull it
towards you. It will slide with just a little effort. Then, to set it,
simply mash the accelerator pedal to the floor. Nothing to it.

Travis

 

[marlene meineken]

I have another question in regards to shifting. When we use the lever to
shift up or down or reverse it seems that the lever almost touches the
steering wheel, maybe a 1/2 inch or less of clearance. Is this normal or is
there an adjustment somewhere?????
Marlene M.

- ----- Original Message -----
From: Travis Martin
To:
Sent: Tuesday, February 01, 2000 7:07 PM
Subject: Re: GMC: Transmission shifting

> > A bit of what I learned on my 76 Birchaven:
> >
> > The kickdown switch is a self-adjusting device. It must be "reset";
then,
> > when the accelerator is first used, the switch "sets" itself. There is
a
> way
> > to reset the switch externally but since I didn't know about this
feature,
> I
> > disassembled the switch to learn it and reset it while I was inside.
> >
> > However, resetting my switch would not have solved the problem: The
> > lubricant in the switch was so deteriorated / coagulated that the
contacts
> > couldn't complete the circuit.
> >
> > It's easy to repair the switch: Carefully bend back the tabs which hold
> it
> > together. Take it apart cautiously, noting the positions of the various
> > parts. I don't recall how many but only a few. A good cleaning and
> greasing
> > will make it work perfectly when reassembled. Be sure to figure out the
> > "reset" position before you reassemble the switch (and how to do it
> > externally, which I forgot!).
> >
> > Ken Henderson
> > 76 X-Birchaven
>
>
> It's easy to reset...just grab the protruding plastic rod and pull it
> towards you. It will slide with just a little effort. Then, to set it,
> simply mash the accelerator pedal to the floor. Nothing to it.
>
> Travis
>
>