Mack Snow Fighter Posted Monday at 04:24 PM Share Posted Monday at 04:24 PM Hello, While driving today, suddenly the 1996 Mack RD688S would not come out of third gear. The shifter is stuck there. Any ideas what went wrong? Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/ Share on other sites More sharing options...
Popular Post Geoff Weeks Posted Monday at 04:55 PM Popular Post Share Posted Monday at 04:55 PM Plenty, but without being able to see and feel, not much help. twisted shaft, bent or damaged fork, interlock fail, shift tower problems, bearing failure, the list goes on. Your going to have to investigate more. 3 Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577599 Share on other sites More sharing options...
fjh Posted Monday at 06:05 PM Share Posted Monday at 06:05 PM Yup trans make? Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577606 Share on other sites More sharing options...
Mack Snow Fighter Posted Monday at 09:41 PM Author Share Posted Monday at 09:41 PM Its a Mack 9 Speed, Haven't found a plate on it yet. Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577629 Share on other sites More sharing options...
Mack Snow Fighter Posted Monday at 09:44 PM Author Share Posted Monday at 09:44 PM Removed the cab floor, and all the bolts on the big cover. Cover seems somewhat stuck. Looks like we might have to drop the trans in order to pull the cab floor. Not enough clearance. Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577630 Share on other sites More sharing options...
mowerman Posted Monday at 09:55 PM Share Posted Monday at 09:55 PM as geoff said im sure its a problem to be addressed from under the top cover,,,might be an easy fix just keep working that top cover,im sure that's all you will need to replace parts good luck,,bob Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577631 Share on other sites More sharing options...
mowerman Posted Monday at 09:59 PM Share Posted Monday at 09:59 PM especially if there was nothing wrong with it pryer to the issue Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577632 Share on other sites More sharing options...
Mack Snow Fighter Posted yesterday at 12:10 AM Author Share Posted yesterday at 12:10 AM Thank you gentlemen for your reply's. We were able to remove the cover only partially, since the transmission is still in the truck. Looked inside and all seems well with the transmission, clutches slide back and forth fine. Put cover back on, added a quart of oil, drove on the road, and she's fine like nothing happened. Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577700 Share on other sites More sharing options...
Joey Mack Posted yesterday at 12:28 AM Share Posted yesterday at 12:28 AM when you had the shifter out, did the slots for the shifter pawl look rounded out as well as the pawl ? It can get stuck in gear or even put it in 2 gears at once. If there is too much wear. Going back to what trans it is.. its a T-2090.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577701 Share on other sites More sharing options...
Mack Snow Fighter Posted yesterday at 12:45 AM Author Share Posted yesterday at 12:45 AM I didn't notice that they were, but I was taking a good look at the forks and the clutches, and not sure if I got a good look. My son who drives it as much as I, says he revved it pretty high coming down a hill when he downshifted, then when it was stuck, it was almost like it was jammed in the wrong gear, in other words it was in third gear, but he wanted first gear. The thought of a worn shifter paw crossed my mind. That wouldn't be hard to change out. Can't get the cover off with transmission in the truck, unless I cut some of the floor out. Thanks for the model on the trans. Looked it up, and yup, that's the one. Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577702 Share on other sites More sharing options...
Joey Mack Posted yesterday at 12:54 AM Share Posted yesterday at 12:54 AM You will need to remove the passenger seat, then you can pull the floor pan . The bolts are 13 mm metric, and theres about 12 of them. Pull the floor mat back at the edges to see the bolts. The throttle pedal will come with that floor panel. It can stay mounted, just disconnect the linkage or wire harness, not sure what you have for an injection pump. Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577703 Share on other sites More sharing options...
mrsmackpaul Posted yesterday at 01:06 AM Share Posted yesterday at 01:06 AM It sounds like a rod all selector fork is loose on a rod On any other brand of box, we're the stick enters the top of the box becomes worn and when you race the gear change the stick comes out of the selector rod dog and leaves the transmission stuck in gear But more detail is needed Paul 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577704 Share on other sites More sharing options...
Mack Snow Fighter Posted yesterday at 01:07 AM Author Share Posted yesterday at 01:07 AM Well that's very good to know. I better do it sooner rather than later, or I'll again be driving the last couple miles home at 12 mph LOL! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577705 Share on other sites More sharing options...
mrsmackpaul Posted 7 hours ago Share Posted 7 hours ago A Mack box is fair bastard to pull out compared to the Road Ranger, however if it has to come out then it has to come out However if the cab is a air ride cab, which I think this is, you can the floor sections out, disconnect the air bag and ride height valve, and probably air cleaners and a few other things and jack the cab up a fairway to get the top off the box, you'll be surprised Getting the top off the box is the easy part, getting it back on is a fiddly job but can be done Don't cake it's mating surfaces in RTV (I think you blokes call it that) or form a gasket stuff, it oozes out inside the box, drops off, gets sucked throught oil pump and plugs all the oil galleries feeding the bearings, then you'll notice you start jumping out of gear as the RTV stops the sliding dogs going all the way in, some ass clown mechanic had done this yo my old bucket of bolts before I owned it, I had to pull the box out amd fully disassemble it and change bearings and a couple of gears and sludimg dogs, theres a few huge days work right there Once you put the lid back on the box, drop the tail shaft off try it through every gear before calling the job done and lowering the cab back down These are things I have learnt the hard way, the very hard way The book (work shop manual) won't tell you any of this, the reality is most of us aren't equipped or flushed with enough cash to pay someone to do this For me, I have learnt this type of stuff on the side of a road or in the shed at home Most mechanics will just fit a change over box and call it done were most times it doesn't cost a fortune I doubt most mechanics would even know how to drop a box apart these days Paul 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75673-mack-transmission-stuck-in-third-gear/#findComment-577760 Share on other sites More sharing options...
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