Hunter013 Posted April 17, 2023 Share Posted April 17, 2023 (edited) Mack GU813 S/N: 1M2AX16C9JM039991. When you're in 12th gear, roughly 1400 rpm and up, the transmission acts like it is trying to shift up another gear, when there isn't anymore gears to go. And when it does that, the rpm dial goes up higher in rpm, rather than lower, like how it would shift normally between gears. All other gears work fine. One code popped up as I was driving. P107492: Gears 2 and 3 engagement system - incorrect performance or operation. Edited April 18, 2023 by Hunter013 Quote Link to comment https://www.bigmacktrucks.com/topic/72745-mack-gu813-code-p107492/ Share on other sites More sharing options...
Mackpro Posted April 19, 2023 Share Posted April 19, 2023 Yours falls into a service bulletin. Looks like probably the ribbon harness inside the transmission. I’ll try to find the bulletin and attach Quote Link to comment https://www.bigmacktrucks.com/topic/72745-mack-gu813-code-p107492/#findComment-529571 Share on other sites More sharing options...
Mackpro Posted April 19, 2023 Share Posted April 19, 2023 Here is the bulletin Mdrive F GU series.pdf 1 Quote Link to comment https://www.bigmacktrucks.com/topic/72745-mack-gu813-code-p107492/#findComment-529574 Share on other sites More sharing options...
QUEST2015 Posted November 8, 2023 Share Posted November 8, 2023 Good evening, I’m having this same issue as we speak, any info on how to repair or a part number for the ribbon harness? Quote Link to comment https://www.bigmacktrucks.com/topic/72745-mack-gu813-code-p107492/#findComment-541606 Share on other sites More sharing options...
Jayphee Posted June 5 Share Posted June 5 I am having the same issue with my transmission, it is disengaging on 6th and 12th gear. Is there someone that can reshare the bulletin mentioned above? Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/72745-mack-gu813-code-p107492/#findComment-553115 Share on other sites More sharing options...
The Heinz Posted June 5 Share Posted June 5 8 hours ago, Jayphee said: I am having the same issue with my transmission, it is disengaging on 6th and 12th gear. Is there someone that can reshare the bulletin mentioned above? Thanks. I'll repost it, here you go. I don't know enough about the technical side of the mDrive to give any further advice other than the ribbon harnesses go bad a lot. If you're looking for it in Impact, it's called the Passthrough Kit. Mdrive F GU series.pdf 1 Quote Link to comment https://www.bigmacktrucks.com/topic/72745-mack-gu813-code-p107492/#findComment-553120 Share on other sites More sharing options...
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