hello... i bought a M1079 to build into a camper... when i drive it up to about 35mph and take my foot off the gas, i hear what seems to be a grinding noise... i thought this might be a bearing going bad or something like that.... so i took it to the only shop i could find that would work on it and had some knowledge of these trucks.... they said that is Normal because it has Straight Cut Gears.... it is still a bit unsettling to me and wondered if this is really normal.... So i am asking here as i know many people own these... i have tried to listen to other trucks on youtube and see if i could hear that sound... but have not? So is this really NORMAL ??? any help would be nice.... thank you
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Coasting Noise?
- Thread starter DMPSound
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coachgeo
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where are you? maybe someone not to far away with similar truck and you can meet up to compare notes/sounds?
PS- you have a build report somewhere?? curious the gizmo room your adding to back of your box.
PS- you have a build report somewhere?? curious the gizmo room your adding to back of your box.
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Check your driveshaft phasing and the set up in the spider gears in your wheel end hubs.
snowtrac nome
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Mine made quite a racket on coasting when a u joint started to fail.
spankybear
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Stuipd question... what is driveshaft phasing.
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the added space to the back of the box is for my bed... it will hold a Full Size mattress... this allows me more room in the box for the bathroom and kitchen and dinette...
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I hate to say it but the chance of ANY repair shop knowing how to set up the wheel end spiders is ZERO. The trained Army mechanics for the most part don't know how. Most shops don't even understand driveshaft phasing. My advise to you is find the threads on Steelsoldiers that explain these tasks and educate your mechs before they make a mess.
coachgeo
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look forward to pics and details on this.
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first let me say THANK YOU to everyone... all very helpful posts 
i checked the phasing on my front shaft... it was only off by 0.2 and that could be from how i was trying to hold my meter as flat as i could... so i dont think that is the problem.... but very helpful information and i didnt even know about this... so i learned something new...
i was hoping that was the problem.... but i guess i have to look into this noise more... i hope its not like some wheel bearing and my front wheel comes off...lol... that would not be good ! and i am afraid to put more money into this truck till i feel it is safe to drive... it only makes this sound when my foot comes off the gas...
thank you all again
i checked the phasing on my front shaft... it was only off by 0.2 and that could be from how i was trying to hold my meter as flat as i could... so i dont think that is the problem.... but very helpful information and i didnt even know about this... so i learned something new...
i was hoping that was the problem.... but i guess i have to look into this noise more... i hope its not like some wheel bearing and my front wheel comes off...lol... that would not be good ! and i am afraid to put more money into this truck till i feel it is safe to drive... it only makes this sound when my foot comes off the gas...
thank you all again
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You have confused driveshaft phasing and driveshaft hinge test.
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Yep google phasing.
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yes... this is what i checked... i also watched a few videos on the subject and was very helpful... thank you again
i can't say enough for the help and this example as well... awesome !!!
Grinding, not a whirring noise? Usually excessive backlash on the ring and pinion makes a whirring sound on decel.
Grinding, might be a bearing like you mentioned. Maybe one that is loaded under acceleration and slack on decel. Pinion and output shafts is worth inspecting. Moving the yoke up and down may show something. Are any leaking?
Next might be u joints. I haven't had much experience with the hub gearsets.
Not sure if the shop checked, but gear oil levels, and the hubs have there own also. Maybe one or more is dry?
Good luck getting it squared away.
Grinding, might be a bearing like you mentioned. Maybe one that is loaded under acceleration and slack on decel. Pinion and output shafts is worth inspecting. Moving the yoke up and down may show something. Are any leaking?
Next might be u joints. I haven't had much experience with the hub gearsets.
Not sure if the shop checked, but gear oil levels, and the hubs have there own also. Maybe one or more is dry?
Good luck getting it squared away.
dbeasty
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I hear what I think is similar grinding from below.. but I think its more somewhat close to grinding/low tone whirring noise that happens to me about the same speed. Sometimes under light gas , sometimes coasting. The noise goes away like after 4 seconds , and does not happen only ocasionally. I kind of dismissed it as not critical, but should I be also looking into the driveshaft phasing?
, and does not happen only ocasionally. I kind of dismissed it as not critical, but should I be also looking into the driveshaft phasing?i would say more of a grinding sound and only when i coast or use light gas pedal and is not there all the time... i think its from the front drivers side... but thats hard to say... at first i thought it could be a transfer case bearing... but i drained it and that was fine... thats also when i learned it shares the fluid from the tranny... im learning as i go here
thanks again for everyone's help ! awesome
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The nature of u-joints is to convert smooth rotation of the shaft into rotation with varying angular speed. The effect increases with u-joint angle. The rapid changes in rotational speed cause a rattle in everything down stream from the joints. Thusly, any play in ring/pinion, spider gears, or either reduction hub causes a rattle. Is it damaging? Probably not. Many of us had this noise. Some tightened the lash in the hubs, some may have adjusted the diff (major job) and some found lack of preload in pinion (easier to fix).
There is, IMHO, another issue going on. As we put many miles on our trucks the rattle goes away. Why? I think the clutches in the drop box for the front drive shaft become more broken in and allow slightly more slippage there. My main LMTV, with about 40k miles added by me, has stopped rattling. Possible clue to this clutch "relaxation" is the higher than expected copper in trans oil analysis. Assuming of course that there is copper in the clutch material.
The front axle seems to pull less with higher mileage, too. Has anyone else noticed that? Btw it still locks solid in MODE.
My advise is to not loose much hair or sleep over driveline rattle. But, sample all fluid reservoirs to be sure there are no wear products beyond normal. Of course the advise on shaft balance and u-joint integrity apply.
There is, IMHO, another issue going on. As we put many miles on our trucks the rattle goes away. Why? I think the clutches in the drop box for the front drive shaft become more broken in and allow slightly more slippage there. My main LMTV, with about 40k miles added by me, has stopped rattling. Possible clue to this clutch "relaxation" is the higher than expected copper in trans oil analysis. Assuming of course that there is copper in the clutch material.
The front axle seems to pull less with higher mileage, too. Has anyone else noticed that? Btw it still locks solid in MODE.
My advise is to not loose much hair or sleep over driveline rattle. But, sample all fluid reservoirs to be sure there are no wear products beyond normal. Of course the advise on shaft balance and u-joint integrity apply.
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On my 1088 someone left out the hub thrust washer. Lucky one of our members sent me one. Maybe you need as NDT said you need to check / set up your hubs. In this case a complete axle service I would recommend.