ZF6 and Cruse Control...Help!

[MaxACL]

While cruising at 70 with the control on, I can accelerate to, say 75 to pass someone and when I get in front and let off the gas, the beast will slow to 65 before it pushes back up to 70 all the while the guy behind me is making obscene jesters toward me for slowing him down. I've been to the dealer three times, once they couldn't replicate it, then they said that

[Wally]

Yep mine does the same thing. I just got in the habit of kicking the cruise off, making the pass and then hitting the resume button. Kind of a pain!

[mackey_62]

Mine too, kind of gotten used to it.
One thing that does bother me.....sometimes trying to use accel button on CC shuts of the CC :mad:

[gun runner]

Same here! Dealer says it's normal. From what I've been told, it's got something to do with not having a torque convertor to absorb rpm changes. Of course ; I thought the auto's locked up?

[Colorado Kid]

That is how mine acts too. I've complained before that I think they just dialed throttle the application rate back too far on these trucks for whatever reason...it begins to add throttle as it coasts down through 70, but it adds it so SSSSLLLLOOOOWWWWLLLLLYYYYY that you're going 65 before it begins to accelerate....then it overshoots by 2-3 MPH as it slowly dials throttle back out. In the above situation I just "catch" the speed myself at about 63-64 MPH and wait for the cruise control to catch up. It only takes a few seconds. When this slow response is really aggravating to me is when I'm towing the 5th wheel between home and Jackson Lake in NE Colorado. US-34 East of Greeley is 4 lanes on rolling terrain (Corregated Land) If I try to run with the cruise set at 65, in either 5th or 6th gear, the speed will vary from 57-73 MPH over and over. If I drive it myself, even in 6th I can maintain 64-66 MPH no sweat, so it isn't a lack of power, just slow application. ON I-70 west of Denver the cruise will hold 68 MPH nicely (due to much more gradual grade changes) right up the steep hills, so it also isn't that the cruise conrol lacks authority, it can apply 100% throttle, it just takes like 10 seconds to get there.

That's the biggest beef I have with my truck, so I guess I'll keep it. ;)

[ 10-23-2002: Message edited by: Colorado Kid ]</p>

[MaxRock]

Mine operates the same way. Slows to 65 or so going downhill and slowly accelerates back to 70. I pass more people going uphill. As their vehicle slows, my truck will hold 70 or maybe accelerate 1 to 2 MPHs...took a while to get use to the way the BEAST operates! Only complaint so far!

MaxRock

[Jelisfc]

Is this a manual trans only problem? Not that it matters my '03 on order has the ZF. It sounds like an issue possibly with the drive by wire.

[GMCTRUCK]

My 03 does the same thing.

[Colorado Kid]

Jelisfc

Yeah it's a ZF only thing...it's our alternative to the Allison's unnecessary downshift routine, and I think they have the same root. If the cruise control was allowed to apply the power faster then the Allison would hold speed without downshifting a lot better, and our trucks would just plain hold speed better.

The old '91 doesn't even have cruise control and I've put a whole bunch of miles on it, so it isn't like this is a deal breaker for me, but it is kind of annoying.

[Jelisfc]

I have a feeling I'll have some interesting comments on my impending Dmax/ZF. The last diesel I owned was a 6.2 and I've got a 200,000 miles driving heavy trucks of all sorts. Never had a problem with cruise control on DDC series 60's. I will happily wait and see.

[C J Fairall]

Getlemen;
Those of you who have an 02 or newer Dmax/6spd with a lazy acting cruise control, I believe that I have the answer (no solution). Early Dmax/Allison oweners had a problem with the tranny downshifting from 5th too soon with cruise engaged. The reason was that the cruise program ws trying to hold an exact speed and therefore added too much throttle, causing an immediate downshift. Good ole GM wrote new software for the PCM allowing the engine to lug down some before forcing a downshift and in many instances no downshift at all. This made the Dmax/Allison owners happy, but we Dmax/6spd owners got stuck with the same program. The reason I know is that my truck used to have a very precise cruise control,but now after a PCM reflash I have the lazy version. I hope this sheds some light on the subject.
Jim.

[MaxACL]

Anyone know how we can make a "Class Action" gripe?

PS I'm using my DuraMax as an income producing truck as of last week. I'm delivering trainers nation-wide and loving it.

Mike

[sally]

I was told the samething that C. J. said. After my truck was reflashed the CC became very lazzy.The dealer said there is nothing he can do to reverse the program. Hopefully the aftermarket guy's can incorporate a CC upgrade in the power loader.