Confused Computer

RickW, on Dec 8 2010, 07:03 AM, said:
Jeff I think the biggest fear is not the complete understanding of the AutoShift.  You have been around trucks but not AutoShifts.  There is a lot of fear when buying used and you do not completely understand it.  That was my HDT buying experience. I was fearful of buying a truck and then having to replace the motor or transmission.  I had never been around HDTs before buying one.  If you read about my buying saga you will find that my worst fears came true even after doing everything right.  But it happens and even when you buy new, things can and do go wrong.

I have had my HDT for 9 months now.  In that time I have done 15k miles.  The only problem I have had with the AutoShift was 1 time when slowing down to make a left turn the truck was in neutral and coasting, I made the left and was then immediately on a road that I was traveling down hill.  The truck would not go in to gear when I gave it some throttle.  I was picking up speed going down the hill.  I think the computer got confused with me slowing down for the turn and then the truck picking up speed with out being in gear.  Once I pulled over and came to a stop the computer was able to figure out what was going on and has worked fine ever since (almost 2k miles ago).  In the future if I find myself in a similar position I now know to burp the throttle so that the truck drops back in gear while still on level ground before I hit the hill and it confuses the computer.

Hi Rick,
I'm trying to understand what happened here so that when we get our truck it doesn't happen to us.  How did your truck happen to be "in neutral and coasting?  Did it automatically shift into neutral when you were slowing down for the corner?  Was it a matter of it not finishing the downshift (being between gears) before you hit the throttle to accelerate again? Thanks

engine - coming up on 1600 rpm
trans - opening the clutch - back off the throttle input
trans - clutch open - drop the throttle
trans shifting gears - doing its thing
trans - input shaft at 1000 rpm
engine - OK RPM at 1000
trans - closing clutch
trans - clutch closed go back to throttle input
engine - go juice applied - making smoke!!

Kind of hokey sounding but you get the idea.

Now if in the middle of all this, you start doing some speed changes (up hill or down hill) and the computer is trying to figure out --- wait, this is not supposed to be there ???  say what???  how did you get to that speed?? ALL RIGHT now, too much for my feeble brain.

But the important thing is -- first law of robotics -- do no harm.  Driver, help me out here, I'm confused.

It has happened to us once or twice.  We were in the mountains going up a steep grade and it decided it was time to downshift again.  It downshift as we crested the grade and were heading down.  So downshift, no load , upshift, engine brake, downshift, all in the space of 30 seconds or so.  I pulled it to manual, let it catch up and then went back to normal.

They may be automatic shifters but, a driver is still required.

(I think they are using some slow processers there and sometimes the mapping does not cover quite everything.)  Looking at some of the newer trucks coming online, they are looking at terrain mapping and GPS sensing in the trucks so they can anticipate (yeah, check that out) the upcoming road and act accordingly. (can you say- too smart for there own good??)

So when slowing down the truck will hit each gear in the high range but typically when in the low range the truck will coast in neutral until you either reach the speed of the gear you have set for take off or you give the truck throttle.  In my example I had slowed down to about 10~15mph to make the left turn.  I was still coasting when turning. I then hit the down hill while coasting, so as Bill explained the computer is very simple and does not understand why the truck is gaining speed.  When I gave it throttle it did not understand how I was gaining speed while out of gear. So instead of forcing a gear it stayed in neutral and started flashing the "Service" light to let me know it did not like what was going on.  Once I was at a complete stop it was able to figure it all out and the service light went out and it started working correctly again

Bill
The terrain mapping stuff is on the too-new trucks (for me).  But should work well.  It "should" keep a driver from having to go to manual in hills to avoid the "flat section upshift" issue. e.g.. "I DON'T want an upshift on this mountain grade, thank you, even though you can.  I can see the hill picking up just ahead."

My background:
Being the eldest of 4 kids, my dad thought it was important for me to crawl around underneath his '48 Ford pickup (with a '53 Merc flathead), holding things for him and handing him wrenches.  I was a cabinet maker for 17 years.  When the last company I worked for was sold and I lost my job I went to college to become a computer programmer.  I was trained for/on "big iron" but did all my writing software on/for "personal" computers, training myself in several languages.  I just recently shut down my servers (all running Linux) and moved the remaining hosted sites to someone else's servers, getting ready to be on the road and mobile.

I appreciate the explanations offered by both of you.

You say that the truck was coasting in neutral.  I assume that's not something it always does when slowing down, but that it was coasting in neutral because the change from high to low range happens slowly and it just hadn't gotten into low/5th yet?

It does sound like a faster processor may be needed, or the software reworked.  Perhaps with the loads that the truck was intended for, situations like this don't happen so often and those aren't needed solutions?

It doesn't surprise me, about the "terrain mapping and GPS sensing".  It seems so much is being done with road and traffic sensing is being done right now in cars and in trucks, where road edges are sensed and the driver "awakened" and, sensing vehicles ahead, automatically backing off the fuel and/or applying brakes.  I wonder how long we have left doing our own driving.

Raquel
UNIX rocks. I run FreeBSD on all my servers. I cut my teeth on SCO, DG-UX, BSD, HP-UX, Sun but worked on SCO boxes for years.

When in auto the truck does not downshift thru the gears in the low range.  Keep in mind that I am under 20mph by the time I hit the low range.  With the short legs of each gear not sure I really want it to downshift thru each low range gear.  At any time I can burp the throttle and it will drop back in to gear.  Now if I am in manual mode than it will downshift thru each gear but it feels like it will throw you thru the windshield once you hit the low range gears with no throttle.

Raquel
A lot of times, especially bobtailing, I will burp the trans into Neutral just to coast up to a light or into a turn.  I figure a neutral pop, coast to the light and back to gear is much smoother than the 8 downshifts.  I try to
drive the next 1/2 mile of road or so.  Smooth and constant.  Many years of riding motorcycles and "They are all out to kill me" attitude.  I can sometimes go a known 30 miles through the city without the brakes.  (Light timing) I try to do the egg under the foot gas pedal thing.  ('Course sometimes, you just have to do the "Yeah, I got the power thing).

I think that what you may see in the future, automated freeways and major secondary roads getting you 10 to 20 miles from major destinations and an offshoot of the hybrids, running electric on the majors and back to the hybrid while on the secondary's. Be an interesting other topic.

Jack Mayer, on Dec 8 2010, 12:58 PM, said:
Rick, in that situation, if you had slid it into Hold and hit the down arrow I "think" but would not swear that it
would have obeyed, and you would have been back in business. Opinions?
On our gen 1 it doesn't "always" work that way. But perhaps it was because of the wire issues mentioned later in

On our gen 1 it doesn't "always" work that way.  But perhaps it was because of the wire issues mentioned later in this post........

The first week we had the truck, (before re-titling as a MH), I used it to haul grain to the river.  First trip, as I was rolling up to a traffic light, in "Hold", I pushed in the clutch and it obeyed all right. I let out the clutch at about 15 mph and killed the motor.  That's when I figured out you have to be stopped and in "N" to restart.  Later I tried it and it would just go to 3rd or 4th, after it figured out where it wanted to be (<10 mph).  So now, I put it in full auto in traffic.

Another trick I've discovered is that often it will not shift into ANY gear from a stop, unless you depress the clutch pedal to the floor to engage the clutch brake.  That one took me a while to figure out, after a lot of bad words.  Boy, did I feel dumb.  Mechanically, ours had been trouble free. Wiring issues are the gremlins to fear.  A couple of corroded wires entering the X-Y shifter caused replacement of that unit, and now I have a bad connector under the cab.  My wife and I can remove the seats/floor in about 1/2 hour now.

Basically the tranny computer throws its hands up and says, "hey dummy what you want me to do"?  Many "commuter drivers" who shift their 4 speed manuals get used to "coasting" with the clutch in, that's a no-no on those big trannies and the newbies need to learn to use the brake coming to turns and force the tranny to shift through the gates while matching the speed of the truck to the right gear.

I don't have a CDL but I've been told that if you "coast" with the clutch in around the corner with the examiner you blow the test.  The idea being that the truck is not being "controlled" when moving and not in gear.  Is that correct?
hjs

that comes from the totally manual transmission world with no synchro gearing.  It makes sure that the truck can provide power or engine control all the way through whatever transition is afoot.

Even coasting with the clutch in is a no-no.  It allows for the ground speed to get out of the safe speed range of the current gear which can theoretically allow bad things to happen.  Again, an item oft debated in olden times.

As for the intermediate shaft brake clutch, that is a "Never while moving" item.  Push the clutch pedal to the floor while moving and you can take out the clutch in a heartbeat.  Some on here have already been there and done that including the legendary ZMan.

There has also been plenty of debate in the early years of this forum about our use of HDTs and how applicable some of these "rules" really are.  The bottom line is not everyone sees SAFE as meaning the same thing including the LEOs but the rules all say the same things.

Our Gen 1 always downshifts to 1st.  Seems like about 1/2 MPH when you finally push in the clutch.

Right now we are troubleshooting or looking for what to do.  Every time we go on one trip we stop for food at a certain exit.  This would be about three hours down the road.  We go in for food, maybe 30 min then head out.  It does the same thing every time, we are on the surface road, reach the overpass to turn left onto the freeway and before we begin to slow for the left turn it won't shift past 3rd or 4th, down the ramp and onto the freeway still won't shift.  Same thing, same spot every time.  Stop, turn it all off, wait, start and maybe it is happy.
Chrissi