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A coworker of my wife asked if I wanted an old four wheeler for free, no details. I went down to pick it up and to my surprise it was a 1998 Honda Fourtrax 4wd. It was last ran in 2010, so I expected it too be junk and I probably wouldn’t keep it. The wheels were locked up, and the gas was from 2010. I got it home, freed the brakes, drained the gas, changed the oil, diffs, and transfer case. It fired right up and I was driving it within 2 hours. So needless to say I scored. Right now I am only going to have to get new wheel cylinders for the front, they are shot, and a carb cleaning. Seems like the idle jet may be a little plugged.

On to my question, I done some searching and have not came up with anything. The drivetrain is silent from 1-4 gears, then when I shift to 5th I hear what I call drivetrain chatter, possibly on the left side towards the front. It makes no noise at other speeds or gears. It goes away on decel. Only seems to be on acceleration and float. Once i speed up and hit around 3k rpms in 5th, the sound goes away. I feel no play grabbing the front drive shaft, cv joints, or rocking the atv back in forth. Clutch was adjusted and feels fine. I am jacking the atv up probably this evening and going to see if I hear it in 5th gear. It really does not seem to come from the rear, but it doesn’t look like you can inspect the rear u joint without removing the swing arm.

Any advise or if anyone has heard something like this, please let me know. I have only owned Suzukis my whole life. I would love to get this thing running well and reliable because I absolutely miss a smaller atv. Thanks!
 

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I jacked the atv up this evening. When I ran the 4 wheeler up to 4th gear, the clatter began. Light throttle, on acceleration only, and the ATV vibrates badly, enough that the floor jacks vibrated the atv around. The sound was coming from the rear of the case. No noises from the front, and the rear differential was quiet. I decided to remove the clutch cover just to take a look. All the gears looked good from what I could see, and I ran a magnet in the bottom of the case to make sure there were no metal pieces. The only thing I found were a couple of sharp brass pieces, they looked orangish and not magnetic. I suppose I am going to put the clutch cover back on tomorrow, the way this thing sounded, I expected carnage. My next guess is, either the u joint on the drive shaft, or the brake is locking up some, causing some backlash in the system. I have no idea what would cause this thing to vibrate so bad. I still hear it most In the case though. FYI the brake drum was warm just from running it on stands for a minute. Brake adjusters are backed all the way out.
 

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inspect the rear differential for bad bearings, yes..it must be removed in order to check them. also inspect the right rear brake bearings in the backing plate.
 

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Here is a video of the sound. Seems to be wheel speed related. You can idle around a parking lot or street around 5mph, no noise.
Attached is the video. Sounds like it is coming in the case at certain final drive speeds. Opened the case on the clutch side, no metal shavings or broken parts. Atv was owned by an old man who used it to hunt twice a year. It actually has tires on it from 2006, the second set.
 

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Here is a video of the sound. Seems to be wheel speed related. You can idle around a parking lot or street around 5mph, no noise.
Attached is the video. Sounds like it is coming in the case at certain final drive speeds. Opened the case on the clutch side, no metal shavings or broken parts. Atv was owned by an old man who used it to hunt twice a year. It actually has tires on it from 2006, the second set.
sounds like the output shaft bearing or carrier bearing for the drive shaft at the rear output shaft. unless its clunking load ?, leave it, let it break down, then you will know for sure what bearing it was. unless you know how to tear them down ?, leave it alone for now.
 

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Discussion Starter #6
Thanks shadetree. Unfortunately it is pretty loud and accompanied by a significant vibration. I wouldn’t ride it far due to fears of it leaving me stranded. It was strange that there was not any large metal shavings in the oil considering the sound it is making. I probably will let it sit for a while, way too many other projects.

Could you remove the output shaft (obviously with the swing arm and driveshaft removed) if you wanted to? It looks like from the manual you DO NOT want to remove the output gear case due to the transmission gears being on the countershaft. But you could possibly remove the output shaft and bearings?

I obviously do not want to split the case, have not done one before, and I also do not want to spend much money on this particular atv. Thanks again!
 

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Thanks shadetree. Unfortunately it is pretty loud and accompanied by a significant vibration. I wouldn’t ride it far due to fears of it leaving me stranded. It was strange that there was not any large metal shavings in the oil considering the sound it is making. I probably will let it sit for a while, way too many other projects.

Could you remove the output shaft (obviously with the swing arm and driveshaft removed) if you wanted to? It looks like from the manual you DO NOT want to remove the output gear case due to the transmission gears being on the countershaft. But you could possibly remove the output shaft and bearings?

I obviously do not want to split the case, have not done one before, and I also do not want to spend much money on this particular atv. Thanks again!
nope, you CAN NOT pull the output shaft, without splitting the cases...like you said..tranny gears will fall off into the lower engine, and ruin your day !..lol.
 

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Bd, if it were me ?, i would start by tearing into the rear drive line, ( rear diff ), and have a look at all the bearings back there, same with the front diff, wheel bearings on front knuckles before tearing into the engine.
 

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I am agreeing with you. I need to replace the rear brake anyway, I have pulled rear diffs apart before in yamahas before due to stripped splines on the ring gear and axle. Not a big deal. I would think I would hear this noise at other speeds and gears if it was in the case or the output case assembly. It wouldn’t take much vibration from the rear driveline to cause backlash in the system ( like the pinion or rear driveshaft unjoint). I am probably wrong, but looking inside this engine with the clutch cover off, it doesn’t appear to be abused or hurt. I appreciate your expertise!
 

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I am agreeing with you. I need to replace the rear brake anyway, I have pulled rear diffs apart before in yamahas before due to stripped splines on the ring gear and axle. Not a big deal. I would think I would hear this noise at other speeds and gears if it was in the case or the output case assembly. It wouldn’t take much vibration from the rear driveline to cause backlash in the system ( like the pinion or rear driveshaft unjoint). I am probably wrong, but looking inside this engine with the clutch cover off, it doesn’t appear to be abused or hurt. I appreciate your expertise!
yvw, glad your attacking this at a easier angle !..lol. keep us posted plz !.
 

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I hate unresolved forums, I decided to not tear the diff apart. I have been cleaning it up, and still doing small maintenance items. I am just going to ride it as is. I have rode it around 5-10 miles around the house the last few days and it seems to be fine besides the noise. Everything is very tight otherwise and it is looking great. I’m 140 dollars in and I’m going to see how far she goes. Thanks again for your help!
 

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Discussion Starter #12
I rode the fourtrax twice since my last post. An easy 18 mile ride with my wife on open roads, nothing severe. I did not hear the noise with here on the back, she weighs about 120lbs. I took it on an additional ride Saturday, 51 miles, varying terrain. It makes the noise way more with just me on it, 160lbs. 1-4th gear normal, shift to 5th and it clunks until my rpms get up to probably 2500rpm or so. I can avoid the noise by winding the engine out in 4th, probably slightly past peak torque, then shifting to 5th. I purposely slowed down in 5th once, let the clutch slip me back up to speed, as soon as you feel the clutch stop doing the work, clunking begins until 2500 rpm or so (by ear).

I do not know if the clutches are grabbing some or what the issue is, but it is low rpm related In 5th. Sounds near the left side of the motor, by the side shaft/ transfer case area. All fluids are new, no shavings when I changed them, Jaso rated oil in the crank case. Turning/ straights make no difference.

I kinda want to fix it now, atv did amazing. No issues other than I need to replace the dry rotted tires and I’m going to do an alignment this week, the left front tire has some significant toe out.



150378
 

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Discussion Starter #13

Here is a video of it shifting into 5th on the road behind my house, it would go away if I sped up faster, only on throttle.
 
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