Allison 6sp: How bad is it

maddogg101920

maddogg101920

I break stuff
Mar 2, 2007
733
0
16
CECIL COUNTY, MD
Was doing some testing in the pulling truck for an upcoming dirt drag event. After a couple 4x4 launches the truck started stuttering when it hit 3rd gear, then I noticed the trans temp gauge was just over 200* (only time I've seen it that high was when I burnt up the stock trans). When I checked the fluid it was a little over an inch low on the dip stick. Filled it back up and things only got worse. Now it won't shift out of first, won't move more then 5ft without giving me the range shift inhibited message and all the abs lights are on and it's saying service break system. Here's a pic of all the codes that popped up for me. Anyone have any ideas if its anything other then the clutches being burnt up?


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THEFERMANATOR

THEFERMANATOR

LEGALLY INSANE
Feb 16, 2009
3,890
43
48
43
ZEPHYRHILLS, FL
Sounds to me like a transfer case issue since you say the ABS and brake lights are on. And you need to connect to the TCM to get the trans codes out. You have the P0700, but no other P07XX codes in that list.
 
maddogg101920

maddogg101920

I break stuff
Mar 2, 2007
733
0
16
CECIL COUNTY, MD
Unfortunately I'm just now getting around to this but I found the issue. Found a couple wires wrapped around the front driveshaft. Problem is idk where the other end of then goes. They are the wires that come off the same group of wires as the speed sensor wires on the transfer case, they were ripped off about 6in past the connector.
y7yhapeb.jpg
 
maddogg101920

maddogg101920

I break stuff
Mar 2, 2007
733
0
16
CECIL COUNTY, MD
Well that didn't fix it. The issue is actually worse. Not only do I get codes from the ECM saying it can't communicate with the tcm but I can't connect to the tcm anymore with efi live. I've checked all connections and grounds.
 
Kappa9012

Kappa9012

MAN.... I Broke it again.
Aug 5, 2008
694
0
16
Peoria Il
Are you sure you got the wiring back together correctly? also like ryan said make sure there wasn't other wiring damage farther up that you didn't see?
 
maddogg101920

maddogg101920

I break stuff
Mar 2, 2007
733
0
16
CECIL COUNTY, MD
I double checked all the wiring. I did have a speed sensor code before I fixed the wiring and now it's gone. I'll check the wiring again when I have a chance but work is crazy right now and don't have much time to work on the truck right now.

I did notice yesterday when under the truck that the wires that seemed to be damaged where the ones for the speed sensor on the t-case. Everything else looked fine.
 
ripmf666

ripmf666

Active member
Sep 20, 2006
15,123
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Wentzville Mo
PhilsLB7 said:
What's the purpose for the wires being twisted in the first place?
Click to expand...

Have to search for the GM service info on it. But they twisted so much of the wire for a reason. I think I also read Someone else talk about replairing this and making sure you have it the same. Something with the magnetic feed going through the wires.

Ok bugged me I searched it down I had posted the info before.

http://www.duramaxdiesels.com/forum/showthread.php?t=32694

The speed sensors are variable reluctance devices that convert mechanical motion to an AC voltage. Each sensor consists of a wire coil wrapped around a pole piece that is adjacent to a permanent magnet. These elements are contained in a housing that is mounted adjacent to a rotating ferrous member. 2 signal wires extend from one end of the housing and an exposed end of the pole piece is at the opposite end of the housing. The permanent magnet produces lines of flux around the pole piece. As a ferrous object, such as a gear tooth, approaches and passes through the gap at the end of the pole piece, an AC voltage pulse is induced in the wire coil. The transmission control module (TCM) calculates the frequency of these AC pulses and converts it to a speed value. The AC voltage generated varies from 150 m volts at low speed to 15 volts at high speed. The signal wires from the sensor are formed as twisted pairs to cancel magnetically induced fields. The cable is also shielded to protect from voltage related fields. Using 2 wire differential inputs at the TCM eliminates noise from other sources.
DTC P0727 is a type B DTC.
 
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