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td83
Senior Member
83 Posts |
 Posted - 01/03/2017 : 02:52:40 AM
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Het all I have a 2006 amtran with Allison trans , that came in with a complaint jerking in gear . test drove bus noticed issue shifting down hard 2x no codes in system at all trans was replaced for this issue , tcm has been swapped out along with a new shift pad to no avail
--basically as you drive at slow speeds the bus shifts down to 1st or 2nd gear when going around at parking lot speeds intermittently, when this happens the shifter pad says 1 or 2 for a quick second then goes back to 5 like its suppose to
the shift pad on theses should always say 5 at all times when D is selected , and when driving on Allison software it also picks up the change of selected gear . I understand its very likely a electrical harness issue but after monitoring all the wire signals to the shift pad when this happens am left with no answers , I checked for any backed out pins at trans connector and checked power and ground from batt to trans harness and fuse holder too . the harness is 20 feet long so just replacing it is easier said than done , taking a shot in the dark in case anyone has seen this what an where was the issue . we already sent the bus out as well and they just charged an arm and a leg to reflash the tcm ?? which had no affect on the issue .
thanks for reading |
Edited by - td83 on 01/03/2017 02:54:53 AM
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RonF
Top Member
867 Posts |
Posted - 01/03/2017 : 05:16:55 AM
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| It would be hard to tell you what do without Allison software to pick up any codes. However there are a few basic things. Fluid and filter changes. Have they been done? You could try replaced the valve body. I've had some over the years do things similar and troubleshooting with Allison software lead me to that. The valve body is around $700. Allison software is around $500, but will save you a tone o cash. You can also "reflash" the TCM with it. |
US Army retired CMBT |
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td83
Senior Member
83 Posts |
Posted - 01/03/2017 : 06:02:32 AM
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| Thanks Ron , yes we do have Allison software and ive monitored everything I know and checked no codes in system , the trans has been replaced for this issue as well . that being said Im definitely leaning towards a intermittent wire issue the only other possible thing I could think of is the engine was recently replaced and our vendor is sometimes sloppy with harness routing ect... don't know if possible something in the engine harness could cause this . But the trans ---the tcm and the shift pad have been swapped with known good parts . |
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torque
Advanced Member
Canada
358 Posts |
Posted - 01/03/2017 : 09:35:18 AM
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The harness is always a good place to check for wired rubbing through. Have had them where the exterior of the harness looks good, but once opened 2 wires have rubbed through one another.
I have also had failing speed sensors on the trans cause the symptom you describe. Usually the front one.
But you say trans was replaced, I assume new speed sensors as well? If so I would have to say in the harness.
Not sure on you unit, but so far for me on Internationals, the wire problems have been on the section of harness on the trans itseld or at the TCM
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td83
Senior Member
83 Posts |
Posted - 01/03/2017 : 10:47:05 AM
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| yes the speed sensors were replaced as well , after going back over today again to no conclusion , I advised foreman was at the point of either removing the harness on the trans (which is quite lengthy and going through the entire thing pulling all the loom off and checking or just replacing the harness ) . I did notice today though I can sit still at times have it in D and issue will happen sitting still shifter pad will say 1 or 2 while not moving at all . Don't know if the Vehicle interface module could cause this issue ?? I know everything else besides the harness has been changed . I will post the fix when we get it back, bossman decided to send out for another try as we have over 500 busses in our fleet cant spend anymore time on it . Thanks for the replies |
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td83
Senior Member
83 Posts |
Posted - 01/04/2017 : 08:01:29 AM
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-bus is fixed , I checked one last time this am , found issue was happening a lot checked on Allison software found wire 153 was changing on and off as an input when issue was occurring no other changes noticed
---traced wire 153 goes from grey tcm connector to dummy plug at rear fuse box pulled wire was chaffed sending ground to tcm and tcm using as input reason for downshifting intermittently
---wire 153 is for optional equipment not installed on this bus reason for no codes for issue I guess
thanks all for the replies |
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g0ttadrift
Advanced Member
USA
258 Posts |
Posted - 01/04/2017 : 1:23:27 PM
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| Thanks for the follow up, good to know. |
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2006 AMTRAN ALLISON TRANS ISSUE
