I just bought a new DMax. Love it so far, but there are a few differences between it and my previous 04 DMax. I have not been able to figure out when it might make sense to use the Manual mode. I'm guessing when I want to ensure it won't shift gears up? My 04 had a "lock" where I could keep the Allison from going into overdrive. Or that was my understanding; I might have the terminology wrong. I drove that truck usually in Tow-Haul.
With the new truck the TH Allison really wants to stay in a lower gear that I think it needs to be. Much more so than the 04, but then again the old truck had one gear less, so maybe that's normal. Also, the 2008 truck only has about 750 miles on it, and I am trying to follow the Manual's recommendation to keep the speed under 50 mph. That's not been easy to do. I don't believe the Allison has been above 5th gear yet, and then only for a little while on a short level stretch.
So, anyone offer a suggestion when to use the Manual mode? The reading I've done indicates using Manual is not really a "manual" transmission, you just limit the top gear, but the Ally will still shift on its own up and down, just not up past the "gear" you selected (like M4). Correct?
FWIW, it LOOKS like my mileage MIGHT be not too bad towing. It is WAY too early to tell. I towed recently with a motorcycle trailer behind the FW and two kayaks on the truck's roof, and my DIC mileage was over 9 mph - which amazed me since I was going pretty slow and the road was twisty and hilly - not much opportunity to get into the high gears. But I am not counting on much yet - another 2000 miles or so towing and I'll track the MPGs - right now I'm afraid I'd scare myself so I've not calculated that - just glancing at the DIC readout.....which is probably a mistake!
Doug and Kathy
2008 Chevy 2500HD extended cab Duramax/Allison 4WD
2007 Crossroads Cruiser CF30SK
"Nuestra casa con buena vistas"
On my 06 3500 DMAX/Alley I leave it in drive and use the TH until it starts searching for gears, up and down shifting, then I use the Manual to hold it in the the lower gear till the road evens out.
I also use manual when going down steep grades to hold the rig in a lower gear.
You are correct in your reading of the operation of "Manual".
My mpg improved after I put some miles on the truck.
We just got back from a 6,500 mile trip with our new Duramax. When we were towing we had it in tow mode and just left it there. The Allison was a wonder, it held the speed both going up and coming down, even the long grade coming into Denver. Because of the cost of diesel we drove 55-60 and got 11.3 towing. Our rig comes in at about 11,500 pounds and I think the mileage will get better with time.
You are right for the manual, as of yet I've not found a need to use it, I just let the Allison in tow mode do it's thing.
One question I have is; when do you change the oil? Do you use the % indicator or change at 5,000 miles. This time I waited until I got home and it had the 6,500, but the indicator said I was at 45%.
Jim & Jane
2008 Cardinal 30TS
Trail Air Pin Box, Air Suspension, Smartair Air Spring Self Leveling, Reese Signature Series 18K hitch
2008 Chevy Silverado 2500HD 4x4 Duramax/Allison Ext Cab Long box Use And Promote CB Channel 13
Put it in "D" and the T/H mode and leave it alone. You paid big bucks for that Allison, let it do it's thing. As for speed control, if you set the cruise going downhill, it will maintain that speed, just like it will do on the interstate cruising.
To answer Traveler II, you should go by the %. I am old school that says change oil every 3,000 and it is hard for me to change. GM has spent mucho bucks to have the computer do its job. You will notice that the percentage drops faster when you tow. I don't remember the figures but, GM figures that this is going to save many barrels of oil.
Does anyone know at what percent the "Change oil now" light comes on? Is it 30%, 20%, 10%, 0%, or what I have been down to 45% with out the "Change oil light coming on. I can't find it in the book.
Othertonka
2004 Southwind 32VS
2002 CRV Toad
U. S. Gear Unified brake system
Retired Fire Captain, SFD
In tow-Haul it will stay in a lower gear longer and You will not see six gear until about 55 or 60, I'm thinking 6th will kick in about 60 mph. If you are in tow-haul and doing about 50-55 kick it out of tow-haul and watch the RPM's drop as it goes into 6th.
I run in TH mode all the time except for heading into or going down a steep grade. I don't feel the Ally shifts down quick enough heading into a grade so I shift to manual and shift down before I start the climb. Seems to work much better. I get between 11.5 and 13 mpg with our 16k lb 5er with 41k miles on it. Oil change...only when it says to. Most diesel mechanics will tell you that you're throwing your money away if you change it like your Grandpa's diesel. Mine goes between 8-10k miles between changes. More important on the changes is your fuel filter....
Scott and Brenda Schnelle
Olivia and Jasmine, Mini Schnauzers
2006 KZ Escalade 36CKB
2006 GMC 3500 D/A(LLY), CC, LB
Fulltimer Class of '06
Lifetime Good Sam's members
Lifetime NRA member
USCCA Member
I keep my Allison in "D" and Tow/Haul. I normally set the Cruise for 100 klicks (62.5 MPH) so that it runs in 6th gear. In that configuration, I'm right at the torque peak of the Dmax and I seem to get the best fuel mileage pulling our 5ver.
The only time I used the "Manual" mode was when I was coming down from the Eisenhower Tunnel to Denver. I was able to control the situation better by limiting the engine speed to about 3200 rpm and the speed to about 55 MPH. I like the Allison's Grade Braking feature for short hills but for long grades, I just don't get warm and fuzzy feelings about the Dmax doing 4000+ rpm.
I use the oil change computer to determine my oil change intervals and normally change the oil when the reading is around 10%. Depending on my truck use, I get about six to eight thousand miles between changes and I use full synthetic oil at each oil change.
Helen & George VE3INB and Max (Bichon Frise) 06 Silverado LT 2500HD D/A 2006 Crossroads Cruiser CF30SK
Prodigy Brake Controller
16K Reese Slider with a Bedsaver
adVentureMan wrote: With the new truck the TH Allison really wants to stay in a lower gear that I think it needs to be. Much more so than the 04, but then again the old truck had one gear less, so maybe that's normal. Also, the 2008 truck only has about 750 miles on it, and I am trying to follow the Manual's recommendation to keep the speed under 50 mph.
With only 750 miles on it the Allison might still be learning. Once you start towing it probably won't seem like its hanging in the lower gears quite as much.
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