grinding/clunking noise in the rear differential..... Question??

[CigarGuy]

I have a 2000, 4x4 Arctic Cat 400. Chain drive. Just recently when plowing my son has noticed a grinding/clunking kind of noise coming from the rear differential area when under a little strain. We added some gear oil and now it grinds just driving up the street. Any thoughts on what it could be?? Thanks. BTW, it only have about 1500 miles on it. Have not used it to plow all that much.

[Dave S]

If it's chain drive, it sounds like the chain may be too loose or the rear sprocket is worn or both. Chains need to be adjusted/lube/maintained on a regular basis.

[piker007]

also change the fluid in the rear diff.

[CigarGuy]

Thanks for the help. We added some 80w-90 gear oil and it started to make noise just normally driving it-not just under strain. Why would it make more noise after filling it. BTW, what is the proper level to fill with gear oil? How hard is it to determine if the chain is too loose? Thanks again. Hopefully, it's something easy-need to finishing plowing the driveway!

[Dave S]

In your first post you mentioned it was chain drive. I thought this wasn't right to begin with and now that I look at a microfiche of the rear end of a 2000 400 4x4 Cat, I am thinking the gear set might be going bad.

Did you notice any shavings or particles when you changed out the rear diff oil?

For your sake, I hope it's not the gear set. It looks to be about a $610 part. If it's the splined end of the left/right axle, you're looking at close to $200 to replace an axle.

[Macgyver55]

Sounds like maybe an axle bearing to me, and whether its a chain drive or differential it has them. They will make all kinds of noise when they go bad, but if it has a differential, it will ruin the gear set too if you keep driving it. Odds are worse depending on how long its been noisy. Either way stop running it right away and check it out because one way or another its going to do more damage.

[CigarGuy]

OK guys, thanks for your thoughts and my bad on the "chain drive". I don't know my head from my butt when it comes to this stuff. Here's some pictures of the part that I believe is screwed up. Behind the boot there is some play with what I think are the gears. What do you think is broken and how much to repair? Thanks again.

[Dave S]

Part #4 in the microfiche view is the one I mentioned yesterday that is $610 according to the price list that accompanies the parts list.

But as McGyver mentioned, it could be a bearing. Without tearing it down, it's hard to tell what the problem is.

[CigarGuy]

any of your guys own a repair shop?

[Dave S]

Not I, sorry. I'm just a sheet metal fabricator.

[quickfish6]

I would drain the fluid and see what it looks like from there. If it looks like there is a lot of metal in there I would tear it down and see what she looks like.

[CigarGuy]

I can get my finger behind the gap in the rubber boot, I can feel bent or distorted metal. I can't tell if it's a seal, bearing or ?. I don't know enough about this stuff to tear it apart. I had a guy on c.list that got my fan going (previous post) and he does drive train work, but he stood me up last Saturday and haven't heard from him since. I think I'm just going to bring it into a shop on Monday. Getting laid off for the winter the end of next week, so I really can't afford a big repair bill right now.