Duramax Diesels Forum Truck of the Week
  #1  
Old 03-07-2008, 11:16 AM
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Default 2-1 hard downshift

My trans has had a hard 2-1 downshift for awile now. It only does it once in the morning when cold. It won't do it anymore until the next mornings first 2-1 downshift. Any thoughts?
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Old 03-07-2008, 11:25 AM
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There is a set of taps that is just for downshifting. When I would run a Kodiak TCM it would knock your teeth out at first.

We need to figure out what to adjust.

Make sure your TCM tune DOES NOT have adaptive downshifting DISABLED.
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Old 03-07-2008, 11:26 AM
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Mine does it too. I hope it's a normal thing.
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Old 03-07-2008, 11:27 AM
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Quote:
Originally Posted by LB7Diesel View Post
My trans has had a hard 2-1 downshift for awile now. It only does it once in the morning when cold. It won't do it anymore until the next mornings first 2-1 downshift. Any thoughts?
Normal in some Alli's.
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Old 03-07-2008, 11:42 AM
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Weird it goes away after you get some heat into the tranny. Is it when you apply the brakes? I ask becomes sometimes mine has some quirky downshifts when braking.

But I'll get a buzzing in the peddle like the ABS is kicking in.
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Old 03-07-2008, 11:56 AM
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Mine does it whether on the brakes or not. I've never had the abs feeling like that though.
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Old 03-07-2008, 12:14 PM
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My truck does it also. I would imagine that it has something to do with the apply and release of the larger clutch stacks, different friction coefficient, and thicker fluid when cold. I think the changes that have been made in a built Alli falls out of the adapt strategy parameter.
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Old 03-07-2008, 12:55 PM
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Great feedback and info guy's, Thanks
As long as Kevin and Mike's truck do it, I'm ok with it
I'm not so sure it's heat that keeps it from continuing to do this.B/c I can go 100ft stop and it'll downshift hard, go another 100ft and it won't do it anymore Maybe it's from sitting all night and things sticking a little.
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Old 03-07-2008, 02:40 PM
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Wendy also does it once in a while.
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Old 03-09-2008, 11:09 PM
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Crazy, very cold here the other night about 29 degrees and mine did it from 2 down to 1. It has never done that before... I warmed the truck up and got up to second gear before the first stop sign. I slowed down and it hit 1st hard. Has not done it since....
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  #11  
Old 03-10-2008, 08:09 AM
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I get it with Tow Haul more than anything, even warm.
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  #12  
Old 03-15-2008, 09:20 AM
LBZ4Me LBZ4Me is offline
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Mine was doing the same thing, and seemed to do it mostly while in Tow/Haul mode while braking hard. Like an ass it was one of the things I complained about to the dealer when my warrantee was about to expire, thinking I wanted to get it on record that there were tranny issues, in case it blew up for some reason :-). Well after I picked it up they told me there was a reflash for the computer. (didn't say if it was a trans or engine flash). I was pissed, I really didn't want them messing with my tune (was back to stock at the time) but was nothing I could do at that point. Now that I'm done bitchin the trans has never hard downshifted since, and it was doing it daily when I took it in. Maybe those knuckleheads actually have a fix????
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Old 03-23-2009, 09:03 AM
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mine does this also. seems to do it when cold and you can feel the abs kick in too. doesn't seem to do it with tow haul on. upshifts and downshifts fine otherwise.
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Last edited by stroke250; 03-23-2009 at 09:04 AM.
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  #14  
Old 03-23-2009, 09:51 AM
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Mine was doing this until I broke it; since I rebuilt it, I haven't had that funky 2-1. Mine did all the stuff described above; goes away when warmed up a little, ABS kicks in...
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  #15  
Old 03-23-2009, 10:20 AM
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from what mike l said(please correct me if i am wrong mike), it seems some just do it and others don't.
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Last edited by stroke250; 03-23-2009 at 10:21 AM.
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