unclebilly Posted November 17, 2012 Share Posted November 17, 2012 (edited) My 95 CH613 gravel truck developed a today. Atleast I noticed it today on the way back from hauling household garbage to the dump...Everything in the driveline seems tight, the tires are good, rough or blacktop doesn't seem to make a difference. The power diverder lockout maight make it louder but it could be my imagination. I drove with the box part way up and cant see anything weird happening with the driveshafts when it clunks.Oh, and it isnt the tail gate clunking, this is what I initially thought it might be but this is what it sounds like.If I roll up the window, I cant hear it.What say you guys? Edited November 17, 2012 by unclebilly Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/ Share on other sites More sharing options...
slpwlker Posted November 17, 2012 Share Posted November 17, 2012 There any freeplay when you take off or slow down? is it from the driveline area, front? Whats the shifter feel like? Vibrating like crazy or very minimul? Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146536 Share on other sites More sharing options...
unclebilly Posted November 18, 2012 Author Share Posted November 18, 2012 There is no freeplay in the driveline (like a cruise control on / off) and there is no vibration in the gear shift. It will do this on a constant climb up a hill. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146540 Share on other sites More sharing options...
slpwlker Posted November 18, 2012 Share Posted November 18, 2012 um getting alittle outside my guesses.Could the hood be moving as the cab moves? I get alot of thunks in my Pete. Alot i have written off others I hunt down. Rubber pad on the back of the cab that the hood comes off and the cab moves it will thunk like crazy. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146543 Share on other sites More sharing options...
David Posted November 18, 2012 Share Posted November 18, 2012 Does it slow down or go away when the truck slows down? Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146555 Share on other sites More sharing options...
rsb502 Posted November 18, 2012 Share Posted November 18, 2012 as above is the clunk constant with driveline speed meaning gets faster as you speed up slower as you slow down, is it every few seconds at the same interval or does it seem to change pace at a set cruising speed? Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146557 Share on other sites More sharing options...
unclebilly Posted November 18, 2012 Author Share Posted November 18, 2012 It is about every 5 seconds at 30 MPH. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146558 Share on other sites More sharing options...
David Posted November 18, 2012 Share Posted November 18, 2012 Sounds like something being moved by the wind. I had a loose exhaust stack do this before. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146560 Share on other sites More sharing options...
rsb502 Posted November 18, 2012 Share Posted November 18, 2012 a clunk at a constant interval with tire rotation leads me to the drivetrain, I dont know what in the driveline is moving slow enough to clunk every 5 seconds at 30mph so that makes me think its the body or frame but it wouldnt be timed with driveline rotation so Im gonna have to go with the only thing I can think of and that is a transmission output or countershaft issue, the gears rotate at a speed consistant with driveline rotation as the gears turn you may have a chipped or broken tooth or pair of teeth that one on a large gear and one on a small gear only come into contact once every two to four revolutions try to keep the truck as quiet as possible on a very smooth road and put your fingertips on the gearshift and put slight pressure to the out of gear side (push ever so lightly like you were pushing it out of gear to put tension on the gears and see if it goes away or you can feel a tick timed to the sound. Another question is this in every gear or just top gear? Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146561 Share on other sites More sharing options...
rsb502 Posted November 18, 2012 Share Posted November 18, 2012 I hope its something i the wind or clunking to a rough road just seems odd to be timed with driveline rotation (faster at one speed slower at another) Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146565 Share on other sites More sharing options...
JumperAndSon Posted November 18, 2012 Share Posted November 18, 2012 Maybe air pressure related? Bleeding off pressure at regular intervals? Just an outside the box guess.Tim Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146568 Share on other sites More sharing options...
David Posted November 18, 2012 Share Posted November 18, 2012 Look for something on top of the tarp or the tarp not retracted tight. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146582 Share on other sites More sharing options...
unclebilly Posted November 18, 2012 Author Share Posted November 18, 2012 I have only noticed this in high range but at 30 MPH, it wouldn't have been in top gear.Could it be a broken axle? Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146583 Share on other sites More sharing options...
unclebilly Posted November 18, 2012 Author Share Posted November 18, 2012 I aired down the bags while i was driving empty and it made no difference. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146589 Share on other sites More sharing options...
rsb502 Posted November 19, 2012 Share Posted November 19, 2012 well if it only happens in high range that gets into another transmission issue it point to the back box in my mind, it might be an axle but you would hear it all the time under power and it wouldnt be so slow the gears in the carriers are spinning pretty quick. Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146819 Share on other sites More sharing options...
slpwlker Posted November 19, 2012 Share Posted November 19, 2012 Is it a thunk or a growl? Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146836 Share on other sites More sharing options...
Lmackattack Posted November 19, 2012 Share Posted November 19, 2012 Might want to have someone follow you in a car and have them pay attention to any sounds from the rear end and transmission. But a clunk every 5 seconds seams like a big interval for a broken tooth on a gear. I would suspect at 30 mph it would be more like every 2 seconds the broken tooth on a gear would come back around. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146837 Share on other sites More sharing options...
57 bcr Posted November 19, 2012 Share Posted November 19, 2012 Do you have hub-piloted wheels on the drives? I had a problem a few years back with a slightly loose set binding then shifting and beating the snot out of the hub until the pilots (4) were badly grooved.They would SNAP & POP.Had a couple guys tell me it sounded like a rear end mssing a tooth! Pulled the rear carrier then pulled the truck outside & it still did it!! DOH!! Glad I was the one that found it,rather than a shop$$$$$!!!! Just a thought! Quote IF YOU BOUGHT IT, A TRUCK BROUGHT IT..AND WHEN YOU'RE DONE WITH IT, A TRUCK WILL HAUL IT AWAY!!! Big John Trimble,WRVA Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146842 Share on other sites More sharing options...
Superdog Posted November 19, 2012 Share Posted November 19, 2012 Do you have hub-piloted wheels on the drives? I had a problem a few years back with a slightly loose set binding then shifting and beating the snot out of the hub until the pilots (4) were badly grooved.They would SNAP & POP.Had a couple guys tell me it sounded like a rear end mssing a tooth! Pulled the rear carrier then pulled the truck outside & it still did it!! DOH!! Glad I was the one that found it,rather than a shop$$$$$!!!! Just a thought!I'm with Al,check your wheels,I cracked an inside wheel once,sure sounded like a u joint Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-146861 Share on other sites More sharing options...
30yearoldjunk Posted November 25, 2012 Share Posted November 25, 2012 Over a dozen years ago I drug my dad's '75 R-model out of the weeds. It did exactly what you are describing. Embarassingly, after a few hundred miles I checked the gear lube in the rears, topped everything off, and no more thump every few seconds. Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-147964 Share on other sites More sharing options...
fjh Posted November 26, 2012 Share Posted November 26, 2012 If it has mack diffs It sounds like a power divider issue to me .Are you running un even tires between axles? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/28408-clunk-every-3-seconds-at-65-mph/#findComment-148140 Share on other sites More sharing options...
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