Hey guys, I bought a Big Bear in non running condition a couple weeks ago. With some carb cleaning and adjusting I have the engine running great. I noticed once It was driveable that it makes a somewhat loud knocking that sounds like its coming from the middle or front of the ATV. I found a loose u-joint on the front driveshaft. I replaced that tonight and changed the diff fluids. Unfortunately, the noise is still there and loud as ever.

I am 99% sure its not coming from the front differential. It doesent make the noise under throttle and it doesent make the noise under deceleration. The only time it makes the noise is when you are loafing along and kind of coasting, and between throttle transitions (like from on the throttle to off the throttle). I didnt replace the U-Joint closest to the engine on the front shaft, but I did grease it and I dont think thats the issue, but im not positive either.

It sounds somewhat as if it could be coming from the engine case. It looks like there is a ring and pinion type setup in there that drives the main center driveshaft by looking at diagrams, but if it was a tooth or something chipped on that, then it would do it on the throttle under load too and it seems smooth then. The only time it makes noise is when there is slack in the driveline.

I just wonder if anyone else has had an issue like this or is familiar with the Big Bear and what could be causing this issue. I was hoping to go ride it Saturday but looks like I may have to take the old Suzuki Quad Runner instead. Thanks

Eric

 

Here is a video of the issue... I took the front shaft out today and it quit making the noise. However, the front u joint on the front shaft is new and the rear joint on the front shaft is in good shape and tight as well. I drove it a little without the shaft and the noise was completely gone. But then I put the shaft back in and its making the noise again. No teeth on the front ring gear are chipped or broken either.

Im starting to wonder if the rear u-joint is shot....

 

Rear U-Joint seems fine... Probably gonna have to start tearing stuff apart to figure this one out...

 

That's really weird. Definitely sounds like it's coming from the engine side. My brother has a 350 Big Bear 4X4, never heard that sound before. Looks like there's a spring loaded cam inside the case where it splines to the ring gear. Can you jack up the rear end and spin the rear wheels while holding the front driveshaft stationary? See if there's any slack in the driveline between the front and rear? Just a thought, I've never had one apart. Let me know if you figure it out.

 

Thanks for the reply. I ended up putting the whole atv up on blocks and running it in place. In the higher gears the rear end was really noticeably loud and whining a lot. I found some really fine metal shavings in there when I changed the fluid. I did check the center shaft and when the front output spins, the rear spins directly with it; no slack there... So since I noticed the noise from the rear end I decided to pull it apart today. Not good... The pinion gear is all eaten up and missing portions of the teeth and there are lots of shavings in the bottom of the housing. The ring gear is eaten up some from the pinion gear but not near as bad as I would think considering how the pinion looks. Honestly I dont know how it wasnt skipping the teeth as bad as the pinion looks. I think it was causing the noise because where there was slack in the driveline, the pinion and ring would bind and free up as they spun, causing the drivehshaft and u-joints to make that mettalic clacking noise.

So I am on the hunt for either a good used rear or parts to rebuild the whole thing with new stuff. Not sure which route im going to go yet, but here are the pictures of the carnage:

 

Ah, good carnage. Ouch. That would definitely cause driveline slack .
Wonder what caused the pinion to frag that bad? Hope you can get it rebuilt, those parts can't be cheap.

 

I guess the bearings got sloppy and made some shavings and then the pinion started eating itself. I guess since the ring gear is larger with more area to spread the load it kept it from wearing as bad as the pinion gear.

Parts arent cheap for sure. $225 for ring and pinion and about $60 for a bearing kit, so right at $300 plus my time fooling with it. I may keep my eye out for a good used one, but im still debating on rebuilding it too.

Its a lesson to pay good attention to what you are buying. In this case I really couldnt have known when I bought it since it wasnt running though. I have $950 in the fourwheeler now. Looks pretty good and runs good with 75%+ tread on a set of ITP Mudlites, so I wont be into it too bad by rebuilding it even though its not something I was planning to do. lol

 

The Good news there must be many Big Bears getting parted out it was one popular ATV and was produced for years so a used one should be easy to get.

Do not just search "2000 Big Bear" on Ebay, I,m sure that rear end has not changed from 1993 to present.
Pre 93 Big Bears were different,they did a change in over in 1993 and got rid of the low range tranny.

 

Yeah there are several differentials on ebay but all the decent ones are over $200. Im kind of leaning towards rebuilding the one I have though. Mainly because It will only be about $75 more than buying a decent used one, and it will all be brand new instead of used so ill know what I have then. The rest of the ATV seems pretty solid, so hopefully with the rear end fixed I can put some miles on it. Need to order parts soon because id like to ride it some while the weather is nice this time of year

 

Ended up with a used one. $236 to my door and got it installed today after work. The Big Bear is running great now. No other issues that I can see. Plan to ride it quite a bit this weekend hopefully so we'll see how it does on my maiden voyage with it.

I ended up buying the used diff because it cost me about $100 less. It was in pretty much perfect condition with just over 1000 miles on it and It saved me a lot of time and waiting on parts since I didnt have to rebuild my other differential. Very happy with how it worked out.