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300 Fourtrax 2x4 ring pinion gear into 250 Fourtrax 2X4 Dif

8416 Views 26 Replies 4 Participants Last post by  retro
So I was wondering if it's possible to use a 300 Ring pinion gear in a 250 Fourtrax Rear diff.. I'm going to replace the bearings and seals, but my 250 Fourtrax's rear end sounds way worse .. it only grinds doesn't move at all so I figured there's gonna be more than just replacing some bearings to it.. All i can find on ebay is a 300 Ring pinion gear.. its cheap.. I want to keep it that way .
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You didn't say which year models you are trying to compare parts for and I'm not sure what you are trying to do.... so here is a fairly reliable parts fiche link where you can compare part numbers:
Honda ATV Parts

It sounds to me like your axle & hubs and/or axle & ring gear may be worn/stripped out judging by your explanation...?

You will need to take the rearend apart and inspect the axle. hubs & diff before spending any money on it. You'll find a copy of the FSM for your ATV HERE if you need one.

The 300 can be upgraded with a stronger rearend from the TRX350 & ATC250ES but requires a bit of fabbing...

Welcome to the forums!
Nope, those parts don't interchange. The 300 has a completely different rearend.
Here are your choices for used ring & pinion (& complete assembly interchange):
41310-HA0-300 GEAR SET, FINAL

Note that ring & pinion gears must be replaced as a set only, as they were machined and lapped in together as a matched pair at the factory. You'll need bearings, seals & probably a few misc shims on hand to set it up properly if you decide to replace them. You'll be better off looking for a complete assembly that is still in good condition. Save both time and money...

You'll need an axle too, if the ring gear splines are stripped. Better to get the entire assembly used and bolt it in...
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either way posted an offer for the atc 250 rear end.. i didn't even think to look that direction for a differential.. thanks for the help there.. but you guys think ill still need a new axle?
You'll have to look at your axle and find out. If the splines are worn (not squared looking anymore) and starting to get sharp, or stripped, you'll need a replacement. You said the ring gear is shot, so ya gotta look at that axle too... those work together and if the axle isn't in nice shape it'll ruin the replacement rearend. You can use partzilla to compare part numbers and wheel bearings like I did for you above.

Snoop around and you may find a better price... ask questions before you buy... don't buy any worn out junk.
You'll need to buy the axle that belongs to the rearend that you buy.

For instance:
If you buy a TRX350 rearend assembly, buy the TRX350 axle to match it.
Why? Because the TRX350 rearend has an axle with much longer splines matching the ring gear width than the 250 axle you linked does. The 250 axle you linked has very short splines for the ring gear and is weak... Its possible that axle isn't what the seller claims either... looks like junk to me.
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worth a shot? the shipping puts it at 50 so idk.. at this point i shoulda bought the whole rear end assembly for 350 or less lol
Thats why you should not buy anything, ever, until you've taken whatever you are working on apart to see what you need. Wastes time and money generally...
You mentioned earlier that you have new wheel bearings for your rearend I think..? Are they OEM? If not, then they are most likely china junk. Whether they are OEM or aftermarket branded, you'll need to pop the rubber seals off from them and pack some high quality grease in each of them. Bearings nowadays are shipped out by the manufacturers with insufficient grease in them... china made bearings may only have a trace of yak fat in them... wash those out good in solvent and blow them dry, then pack them with high quality grease.

Be careful taking those rubber seals off... use a very small and narrow flat blade screwdriver to begin to pry it out on the outer diameter of the seal only. Never poke anything under the seal lip on the inner diameter of the seals cause they are thin and fragile and will be ruined if you try. If a seal gets bent a little when you are popping it off, flatten it back carefully in your fingers before walking them back in place by squeezing the outer diameter (and sliding your fingers along) of those seals between your fingers carefully.

You'll get decent bearing life by repacking... and you'll be buying them again if you don't.
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they're cheap china ones pretty sure .. i'll see if i even install them in the new diff i ordered.. may ride it out with whats in the new one if they are any good. the shaft I'm looking for is a 250 fourtrax rear end 85-87 like what my fourwheeler already has since the king nut won't come off.. the rear end diff i bought is the atc 250 rear end..
Sounds good, have fun with it!
Partzilla is your friend... :)

Honda ATV Parts 1986 TRX250 A SWINGARM Diagram

Clean & repack your old wheel bearings too... they will live for a long time well maintained.
There are no shortcuts throughout life that will allow you to avoid consequences. Any job worth doing is worth doing your best! So, do your best and you'll be rewarded, do less than your best and you'll suffer the consequences... pop the seals off from those wheel bearings and repack them all... :)
Clean & repack the swingarm bearings too. Replace any that are worn into the outer race a lot or have rusty appearing grease in them. If the seals are going bad replace those too. Else I may grab ya by the short hairs an' flog ya...! lol

I'm sure you'll do a great job...
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