Matt, just what I was hinting at. I just didn't want to go there with this
thread. I went to GM Training at the Tigard center annually to keep up my
certification from about 1977 until 1985 or so. We worked on Cruise
controls and HEI a bunch. A/C too. Transverse diesels in Olds wagons were
an eye opener for sure. As was the early ECM/BCM stuff. It all showed up in
one form or another in the GMC. I still have the training manuals for all
of it, and I drag them out once in a while, too.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
> > Jim,
> > > Shifts would be spaced to take ideal advantage of the engines torque
> > curve. Alas, in the 70's, not so much.
> > so is the transmission suppose to kick into a lower gear automatically
> at all, or only by doing a kick down? Is it safe to just switch to S while
> > on cruise control, or are there things one should be aware of
>
>
> Oh Boy,
>
> I was going to stay out of this, but it has walked over into a series of
> problems that I was engaged to fist-fight many years ago.
>
> Theoretically:: If you are encountering a grade with the vehicle on its
> cruise control, the speed regulator (we say cruise control now) should keep
> pulling the throttle open until it hits the transmission kick down
> switch. That is what the design guide says.....
>
> In actuality, there are problems.
> One is that frequently the cruise control servo (the diaphragm thing) does
> not actually have enough range of authority (pull-travel) to pull the
> throttle to WOT.
> Even if it did, by the time the vacuum (aka manifold pressure aka intake
> depression) is shot so there isn't enough of it to pull hard enough to get
> you to WOT.
> And when we worked our way around those two, then we found that often the
> kickdown switch was so mis-adjusted that even if the command is WOT (oops,
> Wide Open Throttle), the contacts were never made to cause the kick-down.
>
> Hydramatic paid our consulting group well to solve this warranty issue.
> As you can see, there was plenty of blame to go around. Hydramatic was
> being
> blamed, and it really was never their problem. We wrote the report, but I
> honestly don't know what they did with it. The subject vehicle was
> actually a big assed Olds or Buick wagon that was near 7k# unloaded. As I
> think of it, if it was loaded to go on vacation and towing a boat, I bet
> the GVW was close to what my coach is.
>
> So, skip all that automagic stuff and use your brain.
>
> Matt
>
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
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