getrdone Posted June 22, 2012 Share Posted June 22, 2012 This is driving me nuts LOL.I have a 1985 MH 613 cabover . The thumping sound is intermitent , does it at weird times . seems to do it more when turning left ,the sound is coming from the right side and seems to be right under the passengers feet . we have looked at everything that can possibly be making contacty with the cab and issolated , shimmed to make tight etc .I was wondering if anyone else has ever had this gremlin and knows what to look for . Thanks , Jerry . Quote Link to comment https://www.bigmacktrucks.com/topic/25794-thumping-sound-1985-mh613/ Share on other sites More sharing options...
j hancock Posted June 22, 2012 Share Posted June 22, 2012 Problems that come and go SUCK!Wish I had the answer but will start throwing things out.Wheelbearing starting to go? Flat spotted tire? Belt separating in tire? I know all these should be "constant" but I did run into a problem with a wheelbearing that if it was loaded just right would show a problem then it would seem to run good.Jim Quote JimIt doesn't cost anything to pay attention. Link to comment https://www.bigmacktrucks.com/topic/25794-thumping-sound-1985-mh613/#findComment-125031 Share on other sites More sharing options...
39 Baby Mack Posted June 22, 2012 Share Posted June 22, 2012 Try looking at the cab bushings---first style were threaded bushings and pins and were greaseable, in my opinion they weren't much.Second style were fiber bushings and straight pins, not much either!Last style was the best- used same rubber bushings as the last F models, these can be retrofitted to earlier trucks, but is to say the least one hell of a lot of work!!!!Try taking a pry bar and inserting it between the bumper and the cab bracket and see how much slop there is.Ron Quote Link to comment https://www.bigmacktrucks.com/topic/25794-thumping-sound-1985-mh613/#findComment-125042 Share on other sites More sharing options...
41chevy Posted June 22, 2012 Share Posted June 22, 2012 Problems that come and go SUCK!Wish I had the answer but will start throwing things out.Wheelbearing starting to go? Flat spotted tire? Belt separating in tire? I know all these should be "constant" but I did run into a problem with a wheelbearing that if it was loaded just right would show a problem then it would seem to run good.JimI agree since it is on a left turn and not straight line, I would take a long look at the the wheel bearings and then the tires. Paul Quote "OPERTUNITY IS MISSED BY MOST PEOPLE BECAUSE IT IS DRESSED IN OVERALLS AND LOOKS LIKE WORK" Thomas Edison “Life’s journey is not to arrive at the grave safely, in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘Holy shit, what a ride!’” P.T.CHESHIRE Link to comment https://www.bigmacktrucks.com/topic/25794-thumping-sound-1985-mh613/#findComment-125043 Share on other sites More sharing options...
getrdone Posted June 23, 2012 Author Share Posted June 23, 2012 Thanks guys , Ron i did the long bar test , its tight , no movement . I should have explained better vit also does it in a straight line, just not as much .I think i may have found it today , There is a lock bolt on the front cab mount , it locks the bushing into place , mine was not in the correct location and the lock bolt was not seated all the way in and was actually loose when i checked it . we tightened the bolt that runs through the front cab mount until the correct area was found to enable the lock bolt to go into the bolt on the hinge area of the mount and when i drove it home i didnt hear the noise any more . Ill keep yall posted on this one LOL. Thanks so much for the brain matter , I can always use another brain or two helping with the gremlins we all run accross from time to time . Jerry . Quote Link to comment https://www.bigmacktrucks.com/topic/25794-thumping-sound-1985-mh613/#findComment-125135 Share on other sites More sharing options...
getrdone Posted June 26, 2012 Author Share Posted June 26, 2012 Yup that was it , the thump is GONE . easy fix once you find it LOL. Thanks fellers. Jerry . Quote Link to comment https://www.bigmacktrucks.com/topic/25794-thumping-sound-1985-mh613/#findComment-125593 Share on other sites More sharing options...
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