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Discussion Starter #1
Maybe its just a Diesel thing but driving down the street 30-40mph I let of the gas and the truck doesn't coast like I would expect it to. It seems like it should be up in a higher gear, almost like the E-brake is slightly applied and dragging if that makes sense and slowing the truck down. No the T/H is not on.

I thought I read somewhere that it will stay in gears longer to heat up if its cold, the gauge barely moves off the 100 degree mark so maybe its doing this on purpose (and killing my MPG at the same time? ;))

I only have 70 miles on the truck as I picked it up last night so I'm still getting used to it. I don't like how soft the trans shifts I can't ever tell what gear the thing is in which is kinda annoying.

Coming home I got up on the highway, crusing along at 80mph its running a little over 2000rpm. Does that sound right? I put it into M mode and I felt it downshift into 5th as indicated on the DIC. I shifted it into 6th and the RPM was the same so I assume its in 6th gear. I guess I thought it would tach lower with 6 gears, but then again its got 3.73s.

It will just take some getting used too I suppose, driving 30-40mph I can never tell what gear its in and the throttle response can be weak at times. I'm coming out of a Supercharged Lightning with really instant throttle response and 500ft/lbs of TQ to the wheels so I probably just need an adjustment period.

This is an 06 LBZ btw :)
 

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Its because diesels dont have a valve to shut off the air. Its the amount of fuel injected and when that decides how much rpm, power not how much air. This being siad therefore the engine constanly pumps with no restriction so that means the engins does little to slow the truck down. \


Someone corrct me if im wrong but this is what i read somehwre i think
 

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The lack of coasting vs. a gasser is a diesel thing and an allison thing, combined -- high compression engine with lots of rotating mass and the effects of t/c lock and unlock and automatic downshifts.

Yes, it stays in a lower gear longer until the trans warms up to within the operating temp range. The bottom of the range is below 100* IIRC, so you won't be able to tell from the gauge. You'll also notice the clutch fan staying on when cold, which makes a loud roar.

On a well-functioning allison in stock configuration you're not going to notice the shifts very much unless you're really into the throttle -- just something you'll have to get used to. If you decide to get an Edge box, the Attitude monitor will tell you what gear you're in.

With the five speed ally and 235/85 tires, I run at around 2200 RPM at 80 mph, so what you're seeing sounds about right for a six speed.

Welcome to the diesel world. It won't be long before you'll be saying "I'll never go back to a gasser."
 

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I Agree With That Siphon !!!!!!!! Got To Love A Diesel
 

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Get the Edge box or whatever and the part throttle torque will keep you away from the gassers forever. Whenever I drive the wifes Tahoe I think "wheres the beef"?
 

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its called,"Engine braking" its normal, and its the torque converter locked in to help slow you down!!!
 

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Well, I have to agree that the Allison is different feeling. I had put 3-1/2 years and 103,000 miles on my 99 6.5TD Tahoe when I traded for my DMax. The first week or so driving the DMax I thought the e-brake was dragging, too. The DMax/Allison just has a different kind of feel when coasting. The Tahoe and 4l80e trans would coast and practically "run-away" going downhill, there's quite a bit of resistance natural in the Allison - must have something to do with the planetary gearing. But, all that being said, your descriptions sound perfectly normal, and I don't recall anyone ever complaining about the Allison shifting "too soft" or too smooth - there's a lot of engineering to achieve that!
 

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Nuthin' from nuthin', but there is no "engine braking" in a diesel. That's why they make "Jake Brakes," exhaust brakes and have those gravel ramps on the interstate. The engine is high compression, but it is an air pump. Even without fuel, the cylinder that is compressed up to 22:1 will "rebound" and you'll get most of that compression work back into the crank until the exhaust valve opens (BTW, that's how a Jacobs brake works, holds open the exhaust valves). The Allison grade braking is to help in this regard. You were exactly right, specialagentPK.
 

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Discussion Starter #12
I don't recall anyone ever complaining about the Allison shifting "too soft" or too smooth - there's a lot of engineering to achieve that!
I like them to shift firm and quick, the smooth soft shifts feel sloppy like the trans is slipping. I'm just used to performance oriented stuff.

It seems to have gotten better or I'm just getting used to it. Truck has 280 miles on it now and feels fine. :)
 

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It seems like it didn't take me long to get used to it. I think you're gonna be very happy with your truck, TTA89.
 

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Idol_chatter,

I meant "Allison grade Braking" thanks for clarifying that up, your right there is no engine braking in these diesel's. Your confusing me w/NUTHIN 4 NUTHIN, WTF, does that mean?????????????????????????????:confused: :confused: :confused: :confused:
 

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It was meant not to sound too critical - like "no big deal"
 
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