Farmall 300 trans/differential damage(long w/pics)

I spent about 5 hours today working on taking the tractor apart. I unhooked the loader and left it in the other part of the shed and moved the tractor into the part with a concrete floor. I took the trans top off after removing a bunch of other stuff and I found that as well as the constant mesh gears which I knew were damaged the bevel gear on trans top shaft and the differential bevel gear are both damaged as well and there are metal bits in the oil channels on the sides. I am wondering if I can assume that if I replace all of the damaged parts and put things together properly the new parts will last or if there can be a more serious problem in the housing or something else on the tractor that could cause the gear damage. I talked to the owner before the auction and he told me that his son-in-law or nephew had put several new gears in the transmission for him and then he had the PTO drive fail and parked the tractor shortly after. Over the summer I fixed the TA and PTO problems with the help of folks on this board and a shop manual, and looked into the front of the transmission while I had the tractor split, at which point everything looked okay except that the retainer was missing off the pilot bearing and the 5th gear splines were worn. I decided not to open up the transmission at that time since I still had not been able to test the tractor. I am wondering what I should do now. I would like to fix the tractor and use it but if that is not practical I can also part it out. I am wondering especially what would do that kind of damage to the differential, I have never seen that before. If I do fix it I am wondering if I should replace all of the bearings in the transmission and rear end since they all presumably have metal bits in them, or if I should try to clean them and reuse them. Any advice will be much appreciated.
Zach

With all the damaged parts I see you should do a complete tear down and replace everything that is bad. I would not use any of the old bearings as a minor blemish now could result in a major repair again later. Probably will be expensive. Is there any possibility of finding a used replacement trans and rear end. That would be easier. Must be some around with blown engine. IMO

I would want to be confident that I found the root cause of the whole problem before I replaced any parts. You are likely to have to tear into further to find that cause.

As for how much I invested in replacing all bearings and everything: I would price all new parts. If reasonable then I would go that route assuming you plan to keep the tractor for peace of mind.

If all new parts are not practical or far exceeds value of tractor then I would also price a mixture of used parts and re-use what I felt confident that I could get away with safely. I would also shop for a whole salvage unit assembly as well and that is likely the cheapest and safest way for the used route.

It's a dilemma.

On one hand if you do a complete tear down and rebuild it will last
another 50+ years and you'll know what you've got. Far cheaper
than buying a new tractor of the same hp and capabilities.

On the other hand 300 class tractors are cheap and easy to come
by. It'd be far cheaper and easier to just go find another one in
better shape.

This is all provided you want/need one.

I have come to the opinion that if a 50-60 year old tractor needs
major engine or trans work it's scrap.

Around here I can buy running Farmall H's,SH's, SC's,M's, 300's in
the $500-3000 range. There's a really good looking SM advertised
locally for $3200. It really looks good in the pics and per owner has
been restored. New tires etc. I can't do one for that.

The wear on the ring and pinion (bevel gears) has been long in the making. To me it is evidence that the "replaced gears" was a patch job, not a rebuild. I would find a donor rear end and swap it out. Or buy the gears and repair it correctly with new bearings as needed. One will cost more in labor and effort, the other has a bit of risk as you will need to look at the donor with a jaundiced eye to be sure you don't have more issues. I really like the 300 tractor, and yours is becoming family(I think). Jim

Thank you, what you said about finding the root cause makes
sense. I am not sure what I am looking for, any advice would be
very helpful. Is it possible that if the backlash or mesh was not set
correctly that that could account for the damage to the differential
gears? I am thinking that the constant mesh gears may have been
damaged initially by other metal getting into them, D Slater said
that the pilot bearing dropping rollers into that area might cause it.
I have not gotten the pilot bearing off yet but I can see that the rear
retainer looks damaged.
Zach

Thank you, the 300 is about the perfect tractor in terms of size and capabilities for what I need to do, mostly small logging and firewood jobs and about 30-40 acres of hayfields. I did think about buying another 300 when I realized how many problems this one had in the summer but I was able to get them fixed for a lot less thanks to getting used parts from D Slater and advice from folks on this forum. If I can fix this transmission and have some confidence that it should last that would be my first choice, but on the other hand I don't want to have to do a semi-annual double split as it is sort of a nuisance.
Zach

Thank you very much, I would like to fix it if all that is needed is to replace the parts that are damaged. I would be leery of another rear end unless I had looked inside it and confirmed that it was in better shape than this one. I will finish tearing it down soon and then I should know what parts I need, I hope. I really liked the 300 when it was working, it was a huge step up in convenience and versatility over the old H. The downside is that I was able to replace the entire H transmission works without having to split the tractor or lift any tremendously heavy parts, but I guess that is the price of convenience.
Zach

I agree about not reusing bearings. If you've got the machine apart to replace gears, replacing the bearings at the same time is a no brainer. Be sure you flush the trans case and rear end very well to rid yourself of metal shavings.

Congratulations, though, on having the guts to tear into your 300 as much as you already have. You have my sincere admiration for doing so. I have never had the guts to split a tractor.

I vote that it's worth fixing and then you'll know what you have.

I'm ok with re-using bearings on a case by case basis. You'll have to clean each one and then examine it. Any roughness, or pitted balls and they get replaced.

In the top photo it looks like the pilot bearing may have let go. I see something that looks like the back of the bearing cage or part of a snap ring. That would be the first suspect.

I'm with Jim in the the ring and pinion wear looks to have been a while in the making. Looks like it's loading at the heal of the teeth and chipping off bits of the ring gear and chewing on the pinion. Could be related since the pilot bearing locates the front of the mainshaft.

The trash in the oil gallery looks normal. Stuff accumulates from people grinding gears etc. I get a package of small rare earth magnets from the hardware store and put one or two on each side and also in the bottom of trans and final case area to hold bits of metal that get worn off.

The damage to the trans gears happened in seconds so there wasn't really time for the debris to circulate through the rest of the trans. The ring and pinion may have been making metal for a longer time but most of that is likely in the bottom of the case.

A second tractor for parts is not a bad idea if you can locate one close and at the right price.
Otherwise, the gears seem to show up on flea bay pretty regularly. Prices all over the place so shop around. Ideally you want the top and bottom to come from same trans. A second tractor would also give you extra pto and hydraulic parts just in case.

The rest of it doesn't look bad at all. Like others have said, you could spend four times the money on a new machine and not have half the tractor. I would fix it and keep plugging away.

I have a 300 RC parts tractor which is almost parted out. I haven't cracked open the transmission yet but will soon. I thought about saving the rear end parts for mine but if you need them to get your 300 back running I'd probably sell them. I'll go see what they look like in the next few days. Where do you live?

Bruce
Rapid City, SD

Don't buy replacement bearings at the dealer. Go to a bearing place or such. I am redoing the bearings in a "H" right now and will save myself over $500 on the axle and bull pinion bearings. Brad

Thanks, I appreciate the tip. All of the bearings I have reached so
far seem to have been replaced recently and to be in very good
shape so I probably will keep them, and even if I have to replace
some I will try to find good used ones since I am a cheapskate. I
have sold some used H axle bearings for $20 a piece and still have
several left, most I have found to be in quite good shape although a
few I have scrapped.
Zach

The prices that I was quoted last friday were not much more than that for new. I think the outer axle bearing was $28 and the inner axle was $27.