Rear pinion falling out

Those plates are for the wet rear brake. If there were chunks missing off the ring and pinion like you say...I surely would not re-assemble with those. It needs new ones installed.

And welcome to the forum.

Thanks for the help! With the case apart the ring and pinion turn free but when its together it will hardly spin. The brake shouldnt have that much drag right? The rear brake was unhooked at the foot pedal when he bought it.

Welcome to GC.

thomas33 said:

Hi thanks all the info here! Im working on 2007 grizzle 350 IRS - YFM35FGIW
It was bought with pinion out of rear diff. We opened the diff and it had a few small chunks missing off ring & pinion and kinda beat up. we cleaned it up and put it back toghther but now when you try to turn it with yoke on it doesnt spin very good. What are the plates that are in the diff? seems like that is the prob. Thanks!

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Welcome to GC from Maine. What wheelsquad said. Don't put broken parts back in. Hope you get it squared away. Should be a fun machine for you when it's all fixed up. We like pictures here!

thomas33 said:

Thanks for the help! With the case apart the ring and pinion turn free but when its together it will hardly spin. The brake shouldnt have that much drag right? The rear brake was unhooked at the foot pedal when he bought it.

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I've never had to work on one myself, so I'm not sure if the brake would affect how freely it spins by hand. I would try activating the brake arm while trying to turn it and seeing if you can notice a difference. If the prior owner had it disconnected, that has me guessing something was wrong with it and he probably didn't want to mess with it. Best bet is to replace all broken parts and get it all working like new. And a service manual will be worth its weight in gold on this project if you don't have one yet. Lots of guys here get theirs from tradebit.

thomas33...Welcome to GC from Wisconsin.

First thing you need is a service manual. Differentials are complex. It would be extremely hard to slap one back together.

The pinion bearing is pressed on the pinion shaft and then pressed into the housing. If it is falling out the housing maybe shot.

Did you install new bearings before putting the diff back together?
If you did replace the bearings, did you properly shim the ring gear to get the proper gear lash?

Your best bet is to download a factory service manual and follow the instructions in it. Replace ALL bearings and seals...no question about that.

Depending on how bad the damage is to the ring and pinion, you might be able to get away with it....or you might not. I'd have to see them in person to make that judgement. In most cases I've had to replace them.
If in doubt at all, replace them.
I have an Arctic Cat front diff apart right now in my garage that chunks are missing from the ring gear, caused by pinion bearing rollers going through it.

dezz said:

Did you install new bearings before putting the diff back together?
If you did replace the bearings, did you properly shim the ring gear to get the proper gear lash?

Your best bet is to download a factory service manual and follow the instructions in it. Replace ALL bearings and seals...no question about that.

Depending on how bad the damage is to the ring and pinion, you might be able to get away with it....or you might not. I'd have to see them in person to make that judgement. In most cases I've had to replace them.
If in doubt at all, replace them.
I have an Arctic Cat front diff apart right now in my garage that chunks are missing from the ring gear, caused by pinion bearing rollers going through it.

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No new bearings, only new parts are the case, seals, pinion shim and snap rings.

He going to need all new bearings. They are pressed on the pinion.

And those pinion and crown gears are in bad shape and should be replaced. If he wants to reuse them, you will need to file down the riser spots of every missing chunk or damage. If this is not done, these "risers" will have metal on metal contact and wear. It will also be tight rotating together, and won't be able to shim it correctly.

And talking about shimming. Since you have replaced the cases, you will need to do a complete re-shimming procedure to get proper gear lash. If shimmed to tight, it will be very hard to rotate and will get damaged during use (which is probably what is happening now). If too loose, the gears could fail under load.

thomas33 said:

I have been working on it for couple months now. Im not the owner im just hlping him out with fixing it. He wanted to try new snap ring and pinion shim and seal , we reassembled and it drove around for ten minutes and pinion came out again. He bought a new case thinking old case wouldnt hold the snap ring. It came out as soon as it went in gear and thats when I figured I better ask you guys.

The pinion bearing is still on pinion and went in new case barely. So if it should be pressed in the new case I guess thats part of prob. He says they dont sell new ring and pinion gears.

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Don't mean to be negative, but those gears look terrible. I wouldn't reuse them.

Vincent said:

Don't mean to be negative, but those gears look terrible. I wouldn't reuse them.

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I have to agree as well, those gears are toast so far as I'm concerned. But as Dezz suggested you "might" be able to get them to work for a little while if you spend some time cleaning them up.....but even then I could see them failing again in the not to distant future. Chances are they used that ring and pinion in a bunch of different makes and models. I had to replace my ring and pinion in my 04 Bruin since the inner splines were toast. Through a bunch of research on-line I eventually found a cross reference list and was able to find a nice used unit from a 99 Grizzly for $60.

The edges of the the gears are probably catching on each other and popping the pinion out ? How is the pinion held in the case? On my 04 Bruin there is a large nut that screws in and holds the pinion in place.

Vincent said:

Don't mean to be negative, but those gears look terrible. I wouldn't reuse them.

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No youre fine. Ive tried to tell him but he wont listen to me.

thrashingcows said:

How is the pinion held in the case? On my 04 Bruin there is a large nut that screws in and holds the pinion in place.

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Im guessing snap ring and bearing?
Thanks guys for the help! I think he is going to try and find a used diff to replace it with.

thomas33 said:

Im guessing snap ring and bearing?
Thanks guys for the help! I think he is going to try and find a used diff to replace it with.

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That is his best option at this point.

X2 find a new used diff.

Check Yamaha Grizzly Swap Shop on Facebook

thomas33 said:

Im guessing snap ring and bearing?
Thanks guys for the help! I think he is going to try and find a used diff to replace it with.

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X3 to that decision. We just put a used diff in an old Honda Foreman 400. Got it from powersportsnation.com Price was right and they guarantee their used parts for 30 days.

Also don't forget that the Grizzly 350 IRS used the same rear diff as some Big Bear, Kodiak, and even some year Grizzly 450, to widen your search.

I found the list of cross reference ring and pinion for my 04 Bruin.....not sure if it will be the same for his quad, but perhaps this might help your friend?

04-06 YFM350A -Bruin
07-13 YFM350G -Grizzly
06-09 YFM350X -Wolverine
99-01 YFM600FW -Grizzly
00-04 YFM400 -Kodiak
03-04 YFM450 -Kodiak
06-10 YFM450 -Wolverine

thrashingcows said:

I found the list of cross reference ring and pinion for my 04 Bruin.....not sure if it will be the same for his quad, but perhaps this might help your friend?

04-06 YFM350A -Bruin
07-13 YFM350G -Grizzly
06-09 YFM350X -Wolverine
99-01 YFM600FW -Grizzly
00-04 YFM400 -Kodiak
03-04 YFM450 -Kodiak
06-10 YFM450 -Wolverine

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These are all solid rear axle bikes right?

He's working on an 07 350 Grizzly with Independent rear suspension. Don't think these parts will interchange.