JD 790 Front Axel

[Tractor King]

I think all kinds of things are going on with these units to tear them up. First and foremost people may be buying too small a tractor for large job. The 790 is a lightweight tractor. Then if the tractor is not properly balance, say 1000 #s on rear. Then if it is used for proper job not like a backhoe. Then if it is used in 4x4 properly no turning heavily while overloaded. Personally I think people are abusing them. A lot of folks think because the tractor is Green it is indestructible.

 

[foggy1111]

We have had a 790 for 3 years, the front axle issues you are experiencing has occured 3 times to us. It has to do with the berings and gears. Each time John Deere has replaced the parts under warrenty and each time it was on the right side. Three weeks ago my tractor broke in half from simply picking up a load of dirt. John Deere does not stand by their product. We struggled to keep the tractor and our small family business has now failed because we owe on a tractor that is useless. John Deere out right said we pulled the tractor apart... My advice.. buy a FORD!

I always wonder about posts like this. I see a FIRST time (or low-count) poster with big problems and some advice like "buy a FORD" or some other brand. Hard to understand the facts of what happened from a single post. :confused2: Well......you likely wont be buying any new Ford tractor soon Callie. I'm just saying........

No doubt these little tractors can have some problems and one should stay within their limitations. But....it IS billed as an economy tractor... and stuff happens.

 

[tessiers]

I run a 790 on a Farm, 5 years and counting, front seals are leaking oil, from my using loader without adaquate ballast, I skid wood with it with a Norse winch, move dry round bales (they say don't do it), all my general farm work. All in all I work it harder than it should be worked and probablly as hard as anyone else, and I have had zero problems. I broke a tractor in half, Massey 1230, they didn't warranty it either, why should they I did it. I lost gears in the front end of that same tractor by using the loader too hard, they did warranty that but shouldn't have, reason I went green is dealer plain and simple. My point is if you want a front end loader buy a 110 or a skid steer, these little tractors (and the big ones for that matter) are beefed up lawn mowers nothing else. Farm I worked on wrecked a 100 hp JD 4x4 loader tractor every year digging silage, bought a pay loader and it has lasted 10 years and counting. Tractors are made for pulling and running implements the loaders are an after thought and should be used as such.

Just my 2 cents.

 

[wdfriesen]

Unfortunately I have the exact same issue. Just curious what they charged you. I bought the ring gear and the pinon plus new bearings. 400.00. I have my hub off and appart but do not have a press or 2 jaw puller. I don't want to start messing with things and then do more damage. Guess I will take the hub in and see if they have time to do this. Only 200 hours on a like new tractor.

 

[spruce Deere]

I have ran a 790 for four years now since new, Not one front end problem loading, pulling, pushing. Even lifting round bales, wet soil and unloading bagged fertilizer. I work it hard, but within reason. I concur that the 790 is not an "ideal" loader tractor, but it can do a lot within its limits.

The 790 seems to have a lighter front end than need be.... My yanmar 240D had a heavier front end that the 790. Just use a little discretion and work around the limits of the small frame tractor.

I have had issues with other areas of the tractor, but it has been purely operator knot-headedness and lack of knowledge

 

[crashz]

My 770 has been a tough little machine, but I try to use 4x4 sparingly. But there are some notablbe changes from the 770 to the 790.

1st, I noticed that the front axle is different. May be stronger or weaker, but its definately a different axle.
2nd, as another poster mentioned, the 770 and early 790's used a model 70 loader, with 54" bucket. And I assure you, the 70 is not a power house. A full bucket of wet gravel has the pressure relief open. Newer loaders, bigger buckets, & high pressure relief settings will put much more pressure on the front axle.

A thing to remember is that the front axle is Mechanical Front Wheel Assist. Not 4x4. Extrodinary forces are produced when digging into a pile, scooping and backing out. Add in the fact that the gear drive makes it difficult to fill the bucket without spinning the tires is worse. Imagine those spinning front tires, suddenly loaded with the weight of scooping bucket full and a quick shift to reverse. I bet the hydro tractors (like the Yanmar/Cub) don't have these issues even with the same frontend.

I've had this in mind when I bought my 770. So when I do loader work, I run it in 2wd with enough ballast to give me moderate traction. Yes, I get some wheel spin. But is easier on the frontend, and I benefit from not slipping the clutch as much.

To the poster who broke his tractor in half: If you broke a 790 in half, you are doing something very wrong. And if you think a Ford/NH will work better for you, my advice would be to seach all the threads on broken tractors. You may change your mind.

 

[totalloser]

I realize this thread is sort of ancient, but it keeps popping up every time I look for a front axle diagram. I have broken front final drive gears several times, they are NOT directional, and I have never broken them in reverse. It's usually been loader work thrashing around trying to get a scoop with a machine that's pretty light. If you don't have enough rear ballast, you really need 4x4 to get a scoop, and that's the start of the problems. Especially since if you lift upward it digs better, but then applies the weight of the pile to the front axle.

What makes matters worse is that the front axle overruns the rear, so when you do this sort of thing, the rear really doesn't to much because the rubber is turning slower than the front. This may be why the r4 equipped 790's run a proportionally smaller front tire. I have 25x8.50r14 R4's on the way (running 7r14 R1's now) to better balance the ratio and remove a little torsional load off the front axle. I don't have grand expectations but expect it to help a bit.

The thing that helped a *lot* was forming up a box on the box scraper, and filling it with scrap iron and concrete. This added about 400 pounds to the back of the box scraper in addition to the scraper weight of about 250 pounds. With a big load of muck in it has trouble due to the lift capacity, but I have top and tilt to wiggle muck back out. With this amount of weight, I can do front end loader work without engaging the front axle. Be aware though, it's not just a function of *weight* it's also a function of where the weight *is*. The further back, the more leverage of the weight it applies to the rear tires. 2wd loader performance with this setup performs almost as well as a 1200 pound backhoe tucked tight to the back.

On mine it's always been the last two gears in the knuckle, and I have never needed a press. Maybe they are not all this way, but on mine everything was tappy tap with a hammer/punch. I have a pretty big press in the shop, but it was never needed. Like others note it's a $400 bummer every time you break one. Rear ballast (and of course water in the tires) helps a LOT and can be pretty cheap. The front axle is not the stoutest, but I am pretty skeptical that it can be broken simply by reversing out of muck or the like. If you break it, you were most likely being mean to it. I have broken mine enough times (4 or 5 times over the years) to have a relatively good idea of why and how.

 

[Kubota 2350]

We have had a 790 for 3 years, the front axle issues you are experiencing has occured 3 times to us. It has to do with the berings and gears. Each time John Deere has replaced the parts under warrenty and each time it was on the right side. Three weeks ago my tractor broke in half from simply picking up a load of dirt. John Deere does not stand by their product. We struggled to keep the tractor and our small family business has now failed because we owe on a tractor that is useless. John Deere out right said we pulled the tractor apart... My advice.. buy a FORD!

I sure would like to know what you were doing when it broke in half, I see you were picking up a load of dirt, but how heavy was it?
Most tractors won't pick up a load of anything that will break them.

 

[totalloser]

I'm with Foggy111. I think Callie was picking up a pallet of balloney with a shill at the wheel.

I may have broken a few gears over the 10+ years I've owned mine, but I have NO regrets with this machine other than being too hard on the front axle. I am using a light duty farm machine for heavy duty construction work. Given that consideration it's held up surprisingly well. I have my hydraulic pressure bumped up too.

Incidentally I forgot to mention the tire sizes I referred to. Mine came with 11.2-24 R1 rears and 7-14 R1 fronts. The rims in the front are 1" narrow (6" instead of 7") for the 25-850r14 R4's I put on, but getting them on wasn't too big of a deal. Strangely the hard part was getting the bead to seat. Straps, Cheeta and high flow failed, liberal application of sledge against the *tread* levered the bead on enough to seat.

Now when you turn, the fronts scrub since they don't over walk the rears (this is good). The tire size ratio varies pretty widely on these machines from about 2:1 with R4 down to about 1.6:1 with R1. But the rears don't change much in diameter. Essentially my R4 fronts gave me a ratio balance comparable to a R4 equipped tractor.