dozerman1 Posted June 11, 2014 Share Posted June 11, 2014 I have a R686St 300+ with 5 speed.I have a hammering noise ,sounds like a tooth missing from a gear.It only does it in 4th and 5th gear.Not noticeable as much while in a pull and vanishes if taken out of gear while rolling down the highway.Is noticeable when downshifting as well but only from 5th to 4th.After shifting from 4th to 3rd noise goes away.Anyone have any ideas?Have checked for metal in transmission and rears and found nothing.Also checked registration with infrared heat gun while driving truck during the work day and all components a simular in temp.Hate to start pulling stuff but not sure how to proceed. Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/ Share on other sites More sharing options...
theakerstwo Posted June 11, 2014 Share Posted June 11, 2014 That sounds to be in trans but you don't say what trans model. Some more info could help. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248911 Share on other sites More sharing options...
dozerman1 Posted June 11, 2014 Author Share Posted June 11, 2014 Sorry Glenn.I believe Mack dealer said it was a trl107.I think that's right.It's just what I call a straight 5 speed with no high or low switch.Seems like everyone calls it something different.Will be glad to look on transmission for more info.Any idea where info would be on it? Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248912 Share on other sites More sharing options...
br549 Posted June 12, 2014 Share Posted June 12, 2014 Sound like it could be a tooth off a ring gear and pinion. Try driving it empty and roll down the window and leave it in 4th or 5th and let it coast down to a low speed and listen for clicking. That is a quick way we check out to see if its in the rear ends. If nothing shows up we put the rears up on stands and run the truck in high gear and listen for the noise. Be sure to remove all rocks from the rear tires if you do this.good luck Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248920 Share on other sites More sharing options...
dozerman1 Posted June 12, 2014 Author Share Posted June 12, 2014 Thanks br549.Truck will make noise at all speeds in 4th and 5th gears.No noise at any speed in 1st thru 3rd.Strange to me that no I see only in 4th and 5th. Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248924 Share on other sites More sharing options...
turckster Posted June 12, 2014 Share Posted June 12, 2014 Drain the oil and remove the 8 hole pto cover, take a look up inside the transmission. Use a pry bar and try to move gears and counter shafts around. If the main shaft has excessive play near the front-where 4/5th gears are at, it could be that the spigot bearing has come apart. With the front 8 hole pto cover off then you will have a chance to look around. The tranny model and serial/part numbers are located above and slightly behind the front 8 hole pto cover, stamped into the case. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248952 Share on other sites More sharing options...
mrsmackpaul Posted June 12, 2014 Share Posted June 12, 2014 might be the big bolt in the tail shaft yoke have had it come loose makes a bit of a rattle but not in all gears I think it lets the out put shaft drift around a bit ????????Paul Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248955 Share on other sites More sharing options...
Superdog Posted June 12, 2014 Share Posted June 12, 2014 are your drive tires all the same height? I had a similar problem years ago after putting on 4 new tires across the back,the difference in height made the power divider want to engage when I shifted into hi gear, sounded like someone beating on the transmission with a sledge hammer 2 Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-248960 Share on other sites More sharing options...
dozerman1 Posted June 12, 2014 Author Share Posted June 12, 2014 Thanks to everyone.Will dig deeper and post what I find. Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-249001 Share on other sites More sharing options...
bbigrig Posted June 20, 2014 Share Posted June 20, 2014 are your drive tires all the same height? I had a similar problem years ago after putting on 4 new tires across the back,the difference in height made the power divider want to engage when I shifted into hi gear, sounded like someone beating on the transmission with a sledge hammerIf the power divider is almost wore out it will bang in and out almost constantly when put under almost any load. I had the same issue when 1 of mine was on its last legs. The divider was engaging and disengaging without a whimper while I was using it daily. But with the wear, it became very noticeable within a few days of use. Quote Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-249865 Share on other sites More sharing options...
theakerstwo Posted June 20, 2014 Share Posted June 20, 2014 Your tires still need to very close in size. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/36022-r686st-with-hammering-noise/#findComment-249869 Share on other sites More sharing options...
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