[Jeepwm69]

Monday afternoon I was messing around in my shop and dug out a 300 diff I'd rebuilt. The pinion gear was tweaked a hair, so I'd set it on the shelf and figured I'd put new gears in it at some point.

I had another 300 diff that had a busted case, but had good gears in it that I tore down later, and I remembered thinking "I can use those gears in that other diff"

So as I dig up a pinion gear, slap it in the 300 diff, and put it back together, I find that it spins over nice and smooth, good teeth contact, and then when I get ready to lock up I realize I'd taken a 350D pinion gear and put it in a 300 diff.

So, I know the gear ratio is the same, and I know the axles on a 300 are much bigger around than a 350 Foreman axle, but it looks like the pinion gears are interchangeable.

I'm going to tear that 300 diff back down and compare the tweaked 300 pinion gear to the 350D pinion gear more closely. I'm pretty sure they're the same.

Just something I found interesting since there are no gear kits being made for the 350 Foreman rear ends.

 

[fishfiles]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

 

[Jeepwm69]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

Really.....interesting.

I'll pull the pinion back and and take some pics of the two.

I have so much crap in my shop everything is getting mixed up.

I've got to organize this crap.

 

[LBZ_Duramax]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

Fish, the 350d (Not 350 Rancher) uses the same chunk as the trx250 and big red. It does use a hypoid gearset not straight cut gearset. The pinions are almost the same. IIRC you have to use the 350d needle bearing as the 350d "nipple" on bottom of pinion is larger or smaller, cant remember which.

 

[SamUK]

This is an interesting thread, looking forward to seeing the differences in these pinions, if any at all.

 

[Jeepwm69]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

Fish, the 350d (Not 350 Rancher) uses the same chunk as the trx250 and big red. It does use a hypoid gearset not straight cut gearset. The pinions are almost the same. IIRC you have to use the 350d needle bearing as the 350d "nipple" on bottom of pinion is larger or smaller, cant remember which.

300 and 350D pinion bearings are the same. Found that out when I had a couple of diff rebuild kits on the bench a while back. Only difference is the 350D doesn't have the retaining wire that the 300 has.

The BR250 and 250A Fourtrax use a smaller diameter pinion bearing.

https://www.thebigbearingstore.com/atv-pinion-bearing-nk14x24-5x15/

 

[shadetree]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

Fish, the 350d (Not 350 Rancher) uses the same chunk as the trx250 and big red. It does use a hypoid gearset not straight cut gearset. The pinions are almost the same. IIRC you have to use the 350d needle bearing as the 350d "nipple" on bottom of pinion is larger or smaller, cant remember which.

300 and 350D pinion bearings are the same. Found that out when I had a couple of diff rebuild kits on the bench a while back. Only difference is the 350D doesn't have the retaining wire that the 300 has.

The BR250 and 250A Fourtrax use a smaller diameter pinion bearing.

https://www.thebigbearingstore.com/atv-pinion-bearing-nk14x24-5x15/

every rear diff from honda has that pesky wire in the needle bearing..EVERY ONE OF THEM ! . unless ????????..they were rebuilt..and not put back in ?.

 

[shadetree]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

Fish, the 350d (Not 350 Rancher) uses the same chunk as the trx250 and big red. It does use a hypoid gearset not straight cut gearset. The pinions are almost the same. IIRC you have to use the 350d needle bearing as the 350d "nipple" on bottom of pinion is larger or smaller, cant remember which.

is correct ^^^, I think fish is thinking trx350 ranchers ?, as their pinion gear teeth are straight, and the old trx350's ( fourtrax and foremans ) have curved teeth.

 

[shadetree]

just a heads up, I really don't think the trx300's pinion gear are the same ?, I just looked at the part number for the 1989 trx350, from 1985 - 1987 trx250 fourtrax, 1985-1986 atc250es, 1986-1989 trx350 the pinion gear and ring gear are the same, but does not list the to fit the trx300's..not one of them ?. soooo..jeep..is it posb you may have grabbed a rear diff from one of the diff's I list here ?. because a trx300 pinion does not show to fix anything but that model ?.

 

[shadetree]

and most important , what is the tooth count on the trx300 pinion gear ?, and what is the tooth count on an old trx350 fourtrax ?. this is where it counts !..lol.

 

[LBZ_Duramax]

Fish, the 350d (Not 350 Rancher) uses the same chunk as the trx250 and big red. It does use a hypoid gearset not straight cut gearset. The pinions are almost the same. IIRC you have to use the 350d needle bearing as the 350d "nipple" on bottom of pinion is larger or smaller, cant remember which.

300 and 350D pinion bearings are the same. Found that out when I had a couple of diff rebuild kits on the bench a while back. Only difference is the 350D doesn't have the retaining wire that the 300 has.

The BR250 and 250A Fourtrax use a smaller diameter pinion bearing.

https://www.thebigbearingstore.com/atv-pinion-bearing-nk14x24-5x15/

every rear diff from honda has that pesky wire in the needle bearing..EVERY ONE OF THEM ! . unless ????????..they were rebuilt..and not put back in ?.

Not all of them, look at a 1985 ATC250ES rear diff breakdown. No wire and not even a hole for the wire. Ive not had a trx250/atc250es diff that had a wire in them.

 

[Jeepwm69]

every rear diff from honda has that pesky wire in the needle bearing..EVERY ONE OF THEM ! . unless ????????..they were rebuilt..and not put back in ?.

Maybe it was the 250A or 250ES. I do know at least one of these diffs I've torn down didn't have the clip, no access hole for the clip and the bearing didn't have the groove for the clip.

just a heads up, I really don't think the trx300's pinion gear are the same ?, I just looked at the part number for the 1989 trx350, from 1985 - 1987 trx250 fourtrax, 1985-1986 atc250es, 1986-1989 trx350 the pinion gear and ring gear are the same, but does not list the to fit the trx300's..not one of them ?. soooo..jeep..is it posb you may have grabbed a rear diff from one of the diff's I list here ?. because a trx300 pinion does not show to fix anything but that model ?.

Anything is possible. I have two TRX250A diffs, a couple of 300 diffs, and probably 4-5 350 Foreman diffs all over the shop. Some are disassembled, so no telling what it fits. LOL. It was sitting next to a 350D housing that I needed a pinion bearing for, and a 300 diff that had the tweaked pinion gear in it.

 

[fishfiles]

you must have had the right pinion with the right ring gear to match , as the cut on the gears between the 350 and the 300 is different between the two , one is straight cut and the other helical cut teeth , I wouldn't even think the two types of teeth would mess together

Fish, the 350d (Not 350 Rancher) uses the same chunk as the trx250 and big red. It does use a hypoid gearset not straight cut gearset. The pinions are almost the same. IIRC you have to use the 350d needle bearing as the 350d "nipple" on bottom of pinion is larger or smaller, cant remember which.

trx350d , atc250es and trx250a all use the same diff , but what Jeep wrote was a 350d and a 300 working together , they are not the same

 

[fishfiles]

from what I remember about the gear ratio difference between the 350d , 250es and 250a and the 300 , it is like .0 something , very , very minimal difference , everyone has been running them for years in place of the 300 oem rear end with out any problems

I am 99.9999% sure that you can't mix a 300 pinion with a 350D ring gear or vice versa , totally different cut on the gears

 

[shadetree]

300 and 350D pinion bearings are the same. Found that out when I had a couple of diff rebuild kits on the bench a while back. Only difference is the 350D doesn't have the retaining wire that the 300 has.

The BR250 and 250A Fourtrax use a smaller diameter pinion bearing.

https://www.thebigbearingstore.com/atv-pinion-bearing-nk14x24-5x15/

every rear diff from honda has that pesky wire in the needle bearing..EVERY ONE OF THEM ! . unless ????????..they were rebuilt..and not put back in ?.

Not all of them, look at a 1985 ATC250ES rear diff breakdown. No wire and not even a hole for the wire. Ive not had a trx250/atc250es diff that had a wire in them.

your right, but I did not go back that far...lol. let me rephrase it, most all the newer atvs, and so far back...use the wire in the needle bearing.

 

[shadetree]

every rear diff from honda has that pesky wire in the needle bearing..EVERY ONE OF THEM ! . unless ????????..they were rebuilt..and not put back in ?.

Maybe it was the 250A or 250ES. I do know at least one of these diffs I've torn down didn't have the clip, no access hole for the clip and the bearing didn't have the groove for the clip.

just a heads up, I really don't think the trx300's pinion gear are the same ?, I just looked at the part number for the 1989 trx350, from 1985 - 1987 trx250 fourtrax, 1985-1986 atc250es, 1986-1989 trx350 the pinion gear and ring gear are the same, but does not list the to fit the trx300's..not one of them ?. soooo..jeep..is it posb you may have grabbed a rear diff from one of the diff's I list here ?. because a trx300 pinion does not show to fix anything but that model ?.

Anything is possible. I have two TRX250A diffs, a couple of 300 diffs, and probably 4-5 350 Foreman diffs all over the shop. Some are disassembled, so no telling what it fits. LOL. It was sitting next to a 350D housing that I needed a pinion bearing for, and a 300 diff that had the tweaked pinion gear in it.

highly unlikely a trx350 ( old school ) pinion gear will fit in a trx300, or vise versa.

 

[mac102004]

The 300 and 350 pinion gears are identical but the ring gears are not. The inner splines on the 300 ring gear are much larger in diameter than the 350 ring gear. Both have helical gears the 350D does NOT have straight cut gears in it.

 

[fishfiles]

here are 300 rear diffs

 

[Jeepwm69]

trx350d , atc250es and trx250a all use the same diff , but what Jeep wrote was a 350d and a 300 working together , they are not the same

Close. The 250's have a smaller needle bearing that supports the pinion (that pinion bearing that it so tough to get out/ replace)

The 350D and 300's have the same needle bearing there, and the 250ES and 240A use a smaller one

Everything else on the 250/350 are the same as far as bearings and seals.

The 300 and 350 pinion gears are identical but the ring gears are not. The inner splines on the 300 ring gear are much larger in diameter than the 350 ring gear. Both have helical gears the 350D does NOT have straight cut gears in it.

Makes sense. That explains why everything fit together ok.

here are 300 rear diffs

HOARDER! LOL