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Andre Wright

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the wire harness is a small one, and it runs over the left frame rail under the cab. I have replaced these due to them chaffing where it goes over the frame edge.   its costs under $150.00 3 years ago when I did the last one...   jojo

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On 9/16/2021 at 6:46 PM, kt_Engineer said:

What transmission do you have? If it is 12-speed MDrive, something seems to be confusing TECU where it is trying to go to low range (from high range) or could not go to Hi-Split in main box. Maybe splitter synchronizer is going bad.

I agree it sounds like the synchronizer this a weak point on the Auto a fairly common  Failure specially I its left with the second speed programing in reverse ! This is a theory  however ! But it Seems to knock the sycro cone loose from the hub due to its design it seems to happen more frequently on those with the two speed reverse program left enabled!

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19 hours ago, Andre Wright said:

Update got my truck back yesterday and its fixed the Mack dealer was right. So apparently a bad transmission wiring harness will cause your transmission to slip

Good to know thanx for posting your fix!

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  • 4 weeks later...

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