JKuhl Posted December 4, 2019 Share Posted December 4, 2019 (edited) The 9 speed in my 98 RD has started jumping out of 4th gear. What confuses me about it is it will not jump out of 8th. I'm assuming the sliding collar is likely worn on the shaft, but normally I thought it would show in both ranges? Am I correct in thinking my problem is in the main box and not the auxiliary? Edited December 4, 2019 by JKuhl Quote Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/ Share on other sites More sharing options...
theakerstwo Posted December 4, 2019 Share Posted December 4, 2019 You are correct 1 Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/#findComment-437237 Share on other sites More sharing options...
theakerstwo Posted December 4, 2019 Share Posted December 4, 2019 But as always for one that is jumping out of gear lift the stick up and check for a weak poppet spring on that rail.Maybe you need to replace that spring and try it before you pull trans. 1 Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/#findComment-437238 Share on other sites More sharing options...
Truck Shop Posted December 4, 2019 Share Posted December 4, 2019 Does the shifter move fore and aft when you let off the fuel or accelerate slightly? More than likely main shaft end play? Would be my thought. Quote One ping only Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/#findComment-437241 Share on other sites More sharing options...
JKuhl Posted December 4, 2019 Author Share Posted December 4, 2019 I've thought about the detent springs, but figure since 8th is ok it's likely not that. The shifter really doesn't seem to move either applying or removing torque. I'm sure I'll be taking it apart after I get done with corn, just was wondering if I was possibly overlooking something. Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/#findComment-437243 Share on other sites More sharing options...
steeler Posted December 7, 2019 Share Posted December 7, 2019 Common issue there, more than likely sliding clutch and gear are worn. I probably do 10 or more a year. While you at it, might as well change the syncro as well. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/#findComment-437512 Share on other sites More sharing options...
Mack Technician Posted December 7, 2019 Share Posted December 7, 2019 You have the double boot in the floor? Shaped like a round accordion? All double boots had to have the inner liner cut out. They were too stiff, but I don’t think they were introduced yet in ‘98. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/60035-eaton-9-speed-jumping-out-of-gear/#findComment-437528 Share on other sites More sharing options...
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