Well rear axle broke on 09 4720...

Ramairfreak98ss · Feb 6, 2015

Well i realized we'd take a chance either way if something was damaged, although the parts alone can be costly, the price of dismantling it at the dealer was going to run into the many thousands, all because it "sometimes had a problem".

It wasn't the diff lock, it seems when i tested it out, it didn't trigger it while locked going forward or reverse or while locking and unlocking while going forward or backwards full turn either way.

I know everyone just assumes it must be how we used "or abused the machine", but i can assure you, this thing hasn't done anything more than 90% of other folks who own one or companies would use it for. I spoke to a company "a snow removal company that has SEVERAL of these 4720 machines that all they use them for is snow removal in North Dakota, severely cold temps usually, running a rear 84-96" snow throwers off the PTO and pushing snow with boxes and big buckets... no issues.

Keep in mind that although we had about 460hrs on it when it first developed, nearly 1/3 or more of those hours are probably idling when doing snow, waiting in parking lots until it snows enough in NJ, just to run the heat in the machine, and another 1/3 are idling and just moving light stuff around the property and for a couple jobs we had the machine on. the other 1/3 hours are pushing snow, bucketing snow, dirt, crushed stone, some digging, and pulling a box blade around on the back.

I'm not saying we baby this thing, but i've put our little simplicity legacy diesel tractor "garden machine" with a 48" bucket through a ton worse, especially for its size and general capability and it has 900hrs on it and no powertrain issues.

None of us expect this no matter how it is used, especially south of thousands of hours on it. The parts that are coming out of the back of this machine are stout. Seems it would take Hercules to break anything.

We found debris in the drivers side axle housing, not much, likely a small retainer cylinder pin that holds a gear onto a shaft, ground up by the planetaries on that axle housing near the parking brake discs...

Took the passenger side axle housing off, no apparent damage there, but after taking off the retainer C clip from the passenger side bearing for the differential, we still can't move it out.

I realized there is the culprit sitting in the oil under the differential, a 3/4" thick roll pin, marred up and chewed up good, then i realized multiple gears about 3" in diameter are lose and just sitting inside the rear differential and causing it to not allow it to slide out the drivers side of the transmission because they're hitting the housing of the transmission. Besides the differential, the planetaries are all good on both sides and the ring gear on the drivers side could use to be replaced, but its slight damage on a couple teeth is not nearly enough to impede its performance in the future. I'm sure every part from deere will cost a ton.

I also won't use our local dealer which, owns all of the AG dealers in NJ now, central jersey equipment after they charged me $300 to come out to diagnose this back months ago, only to tell me that they'd have to bring it into the shop. Well i called for a tow and instead they just "diagnosed" that it needs to come in, and they said it likely needed a hydraulic control unit , "a PCM" computer, i knew that wasn't right though. I argued the $300 bill and even though they could not explain or make sense of the charges, ended up paying $180 of it. The dealer has gone way down hill since they got so darn big...

I'll order parts from a dealer in Ohio if i have to LOL.

Ramairfreak98ss · Feb 6, 2015

Here are two pictures, i have more but this was only ones taken with my phone, poor quality of course lol.

Ramairfreak98ss · Feb 6, 2015

and actually the tractor is in a bay with a 2 post car lift, i have two of the lift arms under the rear fenders under the cab, had to unbolt the bushings and frame of the back that the cab sits on, to move out of the way to remove the passenger side axle housing, and the cab is resting on the lift post arms, one is touchy b/c its all fuel tank so we have it blocked off so the wood is between the lift arm pad and resting on a bolt that holds the tank in place so it wouldnt crush or puncture the fuel tank on the drivers side.

AKfish · Feb 6, 2015

You're gonna know your tractor "really" well, by the time you get everything put back together! Do appreciate your posts as well - long distance learning - is much preferable than actually having hyd oil running down your elbow, heading for your armpit!

Just to clarify things a bit, did one of the axles actually break; or just seize up?

Thanks.

AKfish

Kyle_in_Tex · Feb 6, 2015

Thanks for posting. It is great if you can show pic's of the repair for the rest of us.

Ramairfreak98ss · Feb 7, 2015

AKfish said:
You're gonna know your tractor "really" well, by the time you get everything put back together! Do appreciate your posts as well - long distance learning - is much preferable than actually having hyd oil running down your elbow, heading for your armpit!

Just to clarify things a bit, did one of the axles actually break; or just seize up?

Thanks.

AKfish

Axles are all good, the diff basically was seizing up, and did break, both small gears and roll pin fell out, well the pin started to move and eventually broke in half, thats what half of that rod shaped thing is in the one photo. The other half was sitting in the bottom 10" in front of the diff.

I have the repair JD manual for this machine so although its against copyright laws to publicize it, i'd gladly email you guys pages for help with parts locations etc. if you ever need it. Its for a 4520/4720 cab 09+ tractors.

ok photos from 1 to 10
1. Tractor disassembled, as much as we need to for the repair by now. I must have 200+ bolts out of it by this point.
2. Diff, i know blurry, but the roll pin retainer pin is still in the diff side, the cylinder pin that you knock out with a punch and hammer, it literally just snapped somehow, thus allowing the roll pin to spin out of the diff, and the locking of the rear axle i was experiencing at random, was when the pin slid out far enough, it actually hit the case of the trans, it ate/carved out a good chunk of it but no cracks or other damage..will get a photo of that soon too.
3. this is the diff locking rod, it takes 5 pins to be punched out, took us over an hour for this alone after taking the whole top rockshaft assembly off the top of the trans, see pic #4, that part is 130+ lbs too. Takes 2 guys for most of this dissasembly.
4. Rockshaft assembly unbolted off top of trans, took over an hour and a half just to get anything out of the way on top to get to the bolts to remove this alone.
5. rear PTO assembly gears, this unbolts off the back of the trans, need to unbolt several bolts that hold the rear hitch plate assembly on from the side and 4-6 bolts on bottom too. Note, it helps to have a 3/8" air ratchet, 1/2" air ratchet, 3/8" good impact "we have a 700ft lb air cat, a 1/2" impact gun "were using a 1100-1200ft lb air cat and still cant break some lose", and a 3/4" impact gun with sockets between 3/4" and 1 3/8ths in size, and a 1/2" breaker bar, extendable if you have it.
6. Two differential gears, these should be mounted inside the differential, they were just floating around in there, doesn't look to be any damage., when the roll pin finally snapped and these no longer touched the diff ring gear, the tractor then had no rear axle move ment.
7. buccket of parts, notice the washers totally demolished, could be worse right!
8. Roll pin snapped inhalf, see side chewed up was what was hitting the trans case and other gears when spinning around crazy. Notice the little pin still in it, but shaved off smooth, other half of that little pin is still in the diff.
9. metal debris all over, look at bottom of case, this is looking at back most part under where the PTO gears sit.
10. inside filter mesh screen, looking in from back of trans, "but i have the phone inside from the differential area for the photo", totally covered with metal shards. On the right side of this, is the 1.25" black pipe that feeds the external JD large hydro filter that then goes up to the front of the machine near the engine for the steering pump i think. We havn't been able to slide the filter out yet because the black metal pipe on the outside of the trans i have disconnected, but its rigid and can't move it anywhere to slide this mesh filter out. It appears we may have to remove the entire external filter assembly and pipes and some other stuff just to change this out too... talk about 1-2hrs extra work around every corner.

Me and two mechanics have been working on this here and there for the last few days. Me and both of them are well versed in mechanics, and differentials, gears, engines, auto repairs etc. This is by far more work than i had expected. I think of it as a huge savings not having a dealer do the work though, I kept thinking it would have been a $2k, 4k, repair bill. Most likely even with a skilled , well versed JD mechanic, this is $120/hr work x 2 techs for half the time and one tech for the other half of the time and a 25-30hr job, so more than likely $5k in labor, filters, fluid, hard parts, gaskets, bushings, roll pin...

Not to mention, we're going to have to have a transmission shop likely install the new roll pin, set the backlash and such before we continue with the repair putting it back together.

Ramairfreak98ss · Feb 7, 2015

other end of roll pin
top of trans, with pinion damaged, diff side is fine though, although it seems mared up a lot on the edge, this edge sticks out just past the diff ring gear so it shouldn't impact anything... if this had to be removed, another 2ft of the trans has to be disconnected "JD says you split it in half", you need customized stands from JD with bolts that hold the tractor up then, and then you can take this out to replace it... im sure JD cost is $500 lol.

Last pic is side of screen inside, where it has to slide out, this pipe is rigid and doesnt move even once unbolted.

Kyle_in_Tex · Feb 7, 2015

Thanks for posting. Good that you have some friends helping.

In the middle pic above, it looks like there's a pinion shaft spiral bevel gear that is chipped or is that just debris?

I have driven out the double roll spring pins before and they are usually a bear to get out. I've made my own punches to do this and I usually drive out the "inner roll" and then the outer roll. Do you think your's came out on it's on? I'm sorry if I've misread your posts.

Wondering what is your plan for getting all the metal debris out? I was just reading a manual on an old engine lathe (full of gears) and it said to run the new lathe with the normal oil for about a month or two. Then on a warm day, add kerosene, take out the drain valve fully to allow it to drain fast. One more flush with kerosene and drain, and then refill with oil. I guess they were worried about bits of gears too.

Nothing is easy the first time around on something like this.

Kyle_in_Tex · Feb 7, 2015

Thanks for posting. Good that you have some friends helping.

In the middle pic above, it looks like there's a pinion shaft spiral bevel gear that is chipped or is that just debris?

I have driven out the double roll spring pins before and they are usually a bear to get out. I've made my own punches to do this and I usually drive out the "inner roll" and then the outer roll. Do you think your's came out on it's on? I'm sorry if I've misread your posts.

Wondering what is your plan for getting all the metal debris out? I was just reading a manual on an old engine lathe (full of gears) and it said to run the new lathe with the normal oil for about a month or two. Then on a warm day, add kerosene, take out the drain valve fully to allow it to drain fast. One more flush with kerosene and drain, and then refill with oil. I guess they were worried about bits of gears too.

Nothing is easy the first time around on something like this.