[RanaExcavating1]

DmaxalliTech,


I have on several occasion experienced the Alli "freewheeling" as I went from a stop to start. Most of the time it happens when I quickly stop and resume. Such as coming to a stop sign and rolling through it.


I think I have the most recent updates since my last service visit. Past that I am beginning to wonder about the Alli. It is certainly not living up to what it has done in the medium to heavy duty classes. How can GM put an engine that has its HP and torque rating so close to the limits of the powertrain? This Alli was supposed to be the end all

but it is limiting our ability to add performance to a very capable engine

.


2001 D/A

 

[dmaxalliTech]

does it catch? The way you describe it, its in between 1 and 2nd. It is confused just slightly and therefore takes a bit to reorganize itself. What your describing for the most part seems normal, but it shouldnt do it on a continuous basis. The allison is only designed to handle the amount of power that the engine can deliver, they dont build it to handle extreme boxes... only what the engine is cabable off

 

[RanaExcavating1]

Yes it does catch and runs fine afterwards. I initially thought it was a fluid level issue. It seemed as if it lost it's pressure do to fluid going to the front of the pan. I will pay more attention to see if it is in between gears (searching).


Thanks for the help. It's nice to have the ability to reach out to you for tech help. I think I can speak for most of the members when I say, you are a Tremendous asset to many of us

.

 

[Frank Blum]

Remember Rana, you cannot have one foot on the brake one on throttle with this drive by wire system. Later! Frank

 

[dmaxalliTech]

Another thing to consider on these slush boxes is that the 2-1 downshift wont occur until the output speed sensor shows 0 rpm. If you roll back into throttle and the oss is showing, say 5, then you could catch it in between its planned downshift which could give you the percieved slip

 

[RanaExcavating1]

DMAT,


I checked the 1-2 searching today and you are on the money! It is in between gears.


When GM upgrades the box for the additional power in 2004, do you think it will be a reprogramming or hard parts?


Are you aware of any "shift kits" available?

 

[CADman_ks]

Another thing to consider on these slush boxes is that the 2-1 downshift wont occur until the output speed sensor shows 0 rpm. If you roll back into throttle and the oss is showing, say 5, then you could catch it in between its planned downshift which could give you the percieved slip

dmaxallitech,


I'm not for sure what you're talking about here. That's not the way that my truck acts at all.


When I come to a stop, my tranny feels like it "let's go" when I'm still rolling at 15-20MPH. The easiest way to describe it, is like you're putting in the clutch on a manual.


This is really noticeable when you are in T/H mode. You can feel it downshift every gear, UNTIL it gets to 1st, and then it just let's go. This really takes some getting used to, because it seems when you need the tranny the most, it's not there.


I know someone else who has commented to me on this same issue.


I guess what I'm saying is that mine doesn't shift into first (or doesn't feel like it does), it feels like it's shifting into neutral to me...


cadman_ks

 

[dmaxalliTech]

The way you describe your t/h operation, its operating normally. Mine does it along with other trucks I have driven. The vehicle speed and the engine speed are at the point where you may not feel the dowshift, another possiblity and I am not sure 100% on this is that the convertor is staying locked on your decell and is hydrolically prohibited from locking in 1st gear. The conv being locked will help prevent your grade braking from being lost in the conv, when locked, its just like a manual trans, direct connection. I dont know if your gonna get rid of it, I havent seen any reason to go after a correction becuase all of the trucks I have driven opertate the same way
Eric

 

[CADman_ks]

I guess what I was referring to was this:

Another thing to consider on these slush boxes is that the 2-1 downshift wont occur until the output speed sensor shows 0 rpm.

specifically the 2-1 downshift part and the OSS reaching 0 rpm.


It FEELS like my tranny shifts OUT of second into neutral once you reach about 10MPH. It does NOT FEEL like it stays in second until you come to a complete stop. This is really noticeable when you're towing a 10,000lb trailer. You can feel every down shift, even the one into second, and then when you get to about 10MPH, it feels like it shifts into neutral.


I'm not really doubting that this is the way that it's supposed to be, I'm just trying to understand what's really going on when that last downshhift happens.


Thanks for all your helpful input. It's really appreciated...

cadman_ks