1994 Yamaha Big Bear Pinion Bearing Collar/Rear Axle

[preppypyro]

Hey guys and gals,

I recently bought a 1994 yamaha big bear 350 with... surprise surprise.. rear diff problems.

I have taken the rear diff all apart and the problem is the pinion bearings are both screwed. (Hope Im using the correct terms) Anyways there is a collar that has 4 "divets" in it that ya can beat on with a punch and it should turn. Well Ive beat on that collar and it is not turning. I have lubed, soaked, heated, cooled, you name it, and that collar will NOT budge.

So as a last ditch effort before I take a die grinder and grind that collar outta there, I thought I would throw a post in here, and maybe someone has some trick or advice they can add that maybe I havent thought of.

Now the axle, taking it out needed a beating, and I ended up screwing up the threads that hold the hub on, and eventually broke them right off. My plan is to drill about an inch hole in the end of the axle, thread it, thread a grade 8 bolt in there, loctite it in, then throw a bead of weld around the bolt. Im thinking for the little light duty puttering around I do with this quad, that this idea should be enough to repair the axle so the hub stays on, rather then fork out big bucks for a used or new one.

Thoughts on both repairs would be great!

[Mudflap64]

My comment on the bearing collars is to make sure they aren't left hand thread. I've done exactly what you are describing.

[preppypyro]

Thanks for the reply. I did beat on the collar both ways, seemingly wont budge at all, either way. I have beaten it so there is getting not much left to beat on haha.

[Ajmboy]

When you heated it, did you heat it up enough? Maybe more heat?

* Added year, make, and model to thread title.

[preppypyro]

Thanks for the reply.

I ended up taking my plasma cutter and cutting a little notch not all the way through the retainer, and it broke loose.

Im thinking what solved the issue was just much greater heat.

So anyone have any opinions about my second repair??

[marioweldinginc]

God bless the plasma cutter. What a great invention

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[Mudflap64]

As for the axle, I'd suggest pinning it . Local machine shop might do it cheap. Even with a grade 8 bolt your concentricity could get messed up, someone with a good lathe and some skill could line it perfect....then your weld should be perfect.

[Mudflap64]

If I'm understanding it correctly, you broke off the threaded portion of the axle that retains the hub to the splined portion of the axle? Or is it a simple keyed axle with a shoulder where the hub simply bottoms out? For a keyed axle I'd say it's fine for putting around but if it's splined I'd suggest something more precise. Sorry about the 2 replies, I was on my phone for the first portion. Got any pictures of the damaged axle?

[preppypyro]

I dont have any pictures right now but I will take one tonight and post it.

But yes your correct when you said that it was the threaded part that holds the hub onto the threaded part of the axle. The threaded part is drilled and has one of those crown nuts that threads on. I dont think the threaded part would need to be "balanced" or anything very precise, cause it just holds the hub on, BUT I can see that it would need to be pretty strong so a guy doesnt lose his hub and wheel while driving.

Im also not familiar with the tterm pinning. If you still suggest pinning, could you enlighten me as to what that is? Thanks!

[Mudflap64]

What my mind is picturing is a broken shaft. By pinning I mean drilling a hole in the center of both piece's of the shaft, inserting a pin( or dowel pin might be a better word ) then when fitted properly you can weld the halves back together. Try an snap a few pics if yah can. I'm a machinist. I fix stuff like that all the time, I guess I'm not visualizing exactly what needs to be done.

[preppypyro]

Just imagine the very end of the rear axle. At the very end is threads where a nut goes on, to hold the hub on, that in turn holds the wheel on. On the link I posted below number 11 is the axle then ya can see where the hub )number 6) goes on the end of the shaft. To hold the hub (number 6) onto the shaft, the end of the shaft is threaded. Thats the "piece" I busted off.

Hopefully that explains it a little better till I can get a picture!

REAR WHEEL Yamaha BIG BEAR 4WD (YFM350FWF) 1994 OEM Parts - Cheap Cycle Parts

[preppypyro]

First picture is the complete rear axle

Second picture is the close up of the end of the axle, with the missing threads.. well.. missing!

[marioweldinginc]

Well since it holds the hub on and doesnt have to be perfectly balanced in your case of low speeds, i would try to drill and tap the end if possible thread in some hard threaded rod, weld it to the axle for extra protection slide the hub on and mark where tje hub ends. Remove tje hub and drill a hole for a cotter pin. put on hub and use a castle nut and cotter pin it on.

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[Mudflap64]

Ok , is see exactly what you've got going on. Doweling that would be a tad difficult. I think Mario has a great idea. The cotter pin would ensure that the nut cant com off. I would do it a little simpler and just drill & tap a hole in the axle then use an aviation grade bolt to hold the hub on. ( aviation bolts have a cross hole drilled thru the head and when you install them you put a safety wire thru the bolt head to prevent it from backing out if it should happen to break loose.) all you'd need to to is add a small hole thru the hub to accept the safety wire.( McMaster-Carr) <----like those. Or you can just make your own using a normal grade 8 bolt.

Edited June 23, 2012 by Mudflap64
added link.

[marioweldinginc]

I was gunna say go the bolt route but i was unsure how hard or a steel the axle was. Wasnt sure if he could tap it either. Thats why i said to weld it also incase the threads werent up to par.

I will order those avi-bolts. We use them on bucket trucks. All the hardware has to be wire tied on boom but we usually get the hardware from the dealer which gets expensive.

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[preppypyro]

Thanks for the replies fellas. Sounds like you guys are in agreement as to my original idea for the axle repair. I tried driling the axle last night and my cheap bits arent up to par, so I will have to take it to a machinist. I have a few contacts so it hopefully wont be too bad on price.

I have a nice stainless threaded rod sitting around that I got from work (I work in a place that specializes in specialty metals)that I was pondering using, but I dont know the rules with welding stainless to non stainless so I think I will either look for the aviation grade bolt, or grade 8 bolt.

Thanks again guys. I have to wait for my rear diff and axle bearing kits from all balls racing to come in, but when they do, I will update with progress, even if I dont run into troubles so this thread may help someone else in the future.

[marioweldinginc]

To weld ss to mild you would use a 309 stainless rod or for MIG, stainless steel wire but unsure of the shielding gas.

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[preppypyro]

Just wanted to update. I ended up taking my axle to a neighbour with a lathe and he drilled a hole in it for me, and ran a tap into it. It should be good to go!

Im just about done throwing the new bearings and seals into the diff, just figured out the gear last (least I think I figured it out haha) and will update if something doesnt work, but so far it looks goods!

[99kodiak400]

Hello I know this is an older thread but I too need some help or insight 😅  the rear end pinion that everyone struggles  with that threaded collar with the 4 divits special tool required  anyway I got that frigger off and the pinion shaft out my question is how do I remove the bearing there's another fixed bearing or collar on top of the bearing and it's not in my rebuild kit and I can't find any info online on these bearings to be changed as most swiped it do to not being able to get the collar bolt off the diff to access the bearings laughing out loud  😂 any help would be great 

[99kodiak400]

Anyone get the bearing changed out successfully in the rear pinion? Finally got the collar off but unsure of the bearing removal it has somthing above it looks like a bearing but maybee a  pressed collar? Any help much appreciated  yfm400 kodiak/bigbear/wolverine 

[Mech]

The service manual says the pinion bearing retainer is left hand threads(but I suppose you already know that), and that the pinion shaft can be tapped out with a soft mallet. Then you can use a puller or a press to remove the inner bearing and the sleeve off the shaft at the same time. To get the outer race of the inner bearing out of the housing they say to heat the housing to 150C and use a suitable punch to remove it. It looks in the diagram that they are using a wedge ended punch to wedge the bearing outer out, but I'd probably try heating the housing then banging the housing down on a big block of wood on a concrete floor hoping it would drop out.

[Gwbarm]

I would wear welding gloves or figure out a way to hold it solid before you heat it, if not as soon as you hit it with the hammer and punch it will bounce out of position and first response is to grab it and position it back , but it is hot and it will burn you, just relaying my expierence.

[99kodiak400]

On 10/10/2023 at 9:39 PM, Gwbarm said:

I would wear welding gloves or figure out a way to hold it solid before you heat it, if not as soon as you hit it with the hammer and punch it will bounce out of position and first response is to grab it and position it back , but it is hot and it will burn you, just relaying my expierence.

Yea correct I got the collar off and pinion shaft out on bench just can't find anything online every rebuild skips this bearing cause of the colat tool required laughing out loud I watched every video on u tube with this type diff and nothing showing the most important part of rebuilding the pinion bearings and seals if anyone has info or pics video even a repair manual wouldn't mind sharing it with me would be awesome I need to get the bearing off the pinion shaft has a retainer type looking like a bearing above it  thanks again for all the info shared on these bikes guys

[Mech]

You'll get that bearing and sleeve off with a three legged puller.

[Gwbarm]

When you get it off, you might want to put the shaft in the freezer overnight before going on with the new bearing. It helps.