JD 790 - FRONT AXLE PROBLEM

[regor66]

I have a 790 with mfwd. I've shelled out the gears in the front axle twice. First time was warranty this time it's on me. JD dealer service manager told me the first time they have seen this problem before and feel it's due to the weight of the fel and contents. I use about 600 pounds ballast in the rear but I either need more or that isn't the problem. Both times it's happened while backing up in 4 wheel drive with a load of sand in the bucket. Anybody else had this problem? If so, any solution?

 

[RoyJackson]

I can't recall the name of the guy. It was a good two years ago. Gentleman had an identical problem (including the failure while reversing)...also once in warranty, once not.
I know he repaired it the second time and have never heard another instance, until yours.

The only thing I can suggest is doing a search on TBN for 790 axle and see what you come up with.
Like I said, it's been 2 years, give or take.

Yours and his are the only 2 790's I've heard of. There was a spat of Kubota's...one of the B series, I think.

What year is your machine?

 

[regor66]

The tractor was bought new in August 04. Guess it's a 04 0r 05 model. I ordered almost $600 inparts this morning. Talked again with the service manager and asked him to call JD about some relief. Warranty on repairs are only good for 90 days. Oh well.

 

[AKfish]

I haven't known of many "repeat" failures on the front gears of the 790. They're a pretty tried and true unit.

That said, my coworker had to replace the ring gear and pinion on his 790 last year. His tractor is about 5 years old now so it was well out of the warranty period when things went south.

He was using the loader to move heavy sand and gravel and felt that he was "using" it pretty hard.... He was using 4x4 to dig into the pile on hard, dry ground --- no slippage.. or very little.

The dealer asked him if it was too much to consider pulling away from the pile with 3/4 a bucket full instead of having the sand filling over the top and spilling out the sides of the bucket!?!

The dealer recommended; in those conditions -- that 2WD with the differential lock would likely get the job done with only a minimal amount of added time.

After hearing of this ---- that's exactly how I use my JD 970 to move dirt, sand, gravel, etc.

Horse manure in the winter and plowing snow is about the only time I use 4x4 and the FEL at the same time.

AKfish

 

[irwin]

I have a 790 with mfwd. I've shelled out the gears in the front axle twice. First time was warranty this time it's on me. JD dealer service manager told me the first time they have seen this problem before and feel it's due to the weight of the fel and contents. I use about 600 pounds ballast in the rear but I either need more or that isn't the problem. Both times it's happened while backing up in 4 wheel drive with a load of sand in the bucket. Anybody else had this problem? If so, any solution?

Hi Roger : just a thought, what tires (R1,R3,R4?) and sizes do you have? Are they badly worn? I Have noticed some new tractors appear to have minimum frt lead tire ratios.. ie: should be .05 to .6 percent. Have figured some out to be less than .05% and some right at .6%
I know your problem is more than likely a collection of circumstances, and weak link something, but Seeing my tractor is very similar, I'd like to know where the mfwd lead stresses are in your failure.
Thanks in advance for your reply, hope this situation gets solved permanently this time...

 

[Flywheel]

Brought my 790 in for a looksee on another issue and the manager asked me if I had my tires filled - I said "yes" - He said well good, they will not cover the front axle componenents under warranty if the rears are not filled - even if you say you use ballast - the fact that he pointed this out on his own leads me to belive they have seen more than a few of these....

 

[irwin]

Brought my 790 in for a looksee on another issue and the manager asked me if I had my tires filled - I said "yes" - He said well good, they will not cover the front axle componenents under warranty if the rears are not filled - even if you say you use ballast - the fact that he pointed this out on his own leads me to belive they have seen more than a few of these....

I wonder how filling the rear tires will help the front axles? It would make sense to have ballast behind rear axle to change the fulcrum aspect and ease the weight off the front axle. The weight (fluid) inside the rear wheels wouldn't take any weight off the front axles..... would it?..It doesn't put any weight on the rear axles (most of it is below the axle) ....... I've heard service people say some questionable things, after all they're only human, and I believe you were told this, but it doesn't make any logical sense to me?????

 

[RoyJackson]

I wonder how filling the rear tires will help the front axles? It would make sense to have ballast behind rear axle to change the fulcrum aspect and ease the weight off the front axle. The weight (fluid) inside the rear wheels wouldn't take any weight off the front axles..... would it?..It doesn't put any weight on the rear axles (most of it is below the axle) ....... I've heard service people say some questionable things, after all they're only human, and I believe you were told this, but it doesn't make any logical sense to me?????

Well, loaded rear tires would increase traction (ensuring those tires have a good bite), thus reducing the traction requirements of the front wheels. Unloaded rears would slip more.
But, you're right Irwin...there'd be no reduction of the vertical loading on the axle.

I can't recall all the circumstances of the failure two or so years ago, but it seems to me we discussed a bad lot (batch) of gears (bad heat treat, improperly machined) as a possible root cause. Since regor66's tractor stems from 2004 (which means it could have been a left over 2003 or a 2005), it's possible the same thing could have happened...just a guess.

 

[AKfish]

I didn't read the posts concerning the faulty gear components. Likely a considerable number of failures if that was the situation. Hopefully, Deere stepped up and took care of the problem.

That said, you can break anything if you work "hard enough at it"....

Gotta use a fair amount of common sense whenever you get in the seat and turn that starter key...

AKfish

 

[RoyJackson]

I didn't read the posts concerning the faulty gear components. Likely a considerable number of failures if that was the situation. Hopefully, Deere stepped up and took care of the problem.

That said, you can break anything if you work "hard enough at it"....

Gotta use a fair amount of common sense whenever you get in the seat and turn that starter key...

AKfish

YOU BETCHA!