JD 790 front end problems

[DWCox]

Made a major discovery today that helps explain some of the problems I have encountered:

The JD dealership I talked to indicated that I needed ca. 400 lbs of ballast with the 300 loader. As most of you indicated, that seemed awfully low. My box blade is 418lbs, so I thought that I was okay.

Wrong.

I should have looked it up myself, so it is ultimately my fault. I looked today and the 300 loader manual calls for a minimum of 617 lb. of 3-point hitch ballast in addition to fluid-filled rear tires. In other words, from day one, I have consistently been running 200 lbs. less rear ballast than is minimally required, and that was before boosting the hydraulic pressure!

What made me decide to double check the numbers was another dealership I called this morning out-of-state, which had one of the washers I needed for the repair. First thing out of his mouth was the question, "having trouble with the front end gears?" Next thing he said was, "you need more ballast in the rear." He likes to get about 1,000 lbs of rear ballast (which includes the filled tires) on the 790.

 

[RoyJackson]

Made a major discovery today that helps explain some of the problems I have encountered...

No doubt a lesson learned...but an expensive lesson! It takes a big man to admit a mistake. You proved you're a tough guy and can handle errors which we all make...some of us just don't admit them.

If there is a silver lining to this cloud, other 770/790/3005 owners will pay heed to this thread.

Good post, DW...I'm sure you won't have any other problems with the front end...once this one is squared away

 

[JDGreenGrass]

Decent...Glad you have discovered the ballast knowledge.

And Roy is right....I have a 770 with a JD Ballast Box. It is filled with concrete minus a few inches at the top. I honestly don't know how much it weighs and from time to time I would think to myself that it may be too much ballast weight.

After reading this thread I am confident that it is NOT too much weight.

And now we know why these little JD tractors are referred to as being "robust" or, allow me to use the word......Stout.!!

DW....Hope this has eased your worried mind. Now, get to work.

 

[AGGIE00]

This just seems nuts to me. A tractor should be engineered to handle its hp capacity without the need for a counterwieght. Planetery drive systems are very durable and what is found in all industrial construction equipment. I bought mfwd primarily for loader work and don't expect to have to add weight to the back to keep from damaging the tractor. I say buy a bigger tractor.

 

[AGGIE00]

So I looked at my manual and it requires 2400# of ballast for my loader. Never gave it any thought before now since all I have ever run is backhoes.

 

[RoyJackson]

This just seems nuts to me. A tractor should be engineered to handle its hp capacity without the need for a counterwieght. Planetery drive systems are very durable and what is found in all industrial construction equipment. I bought mfwd primarily for loader work and don't expect to have to add weight to the back to keep from damaging the tractor. I say buy a bigger tractor.

Well, bigger tractors require ballast too.
Since you mention industrial equipment...take a closer look next time. They have huge permanet counterweights built right into them (big thick castings). So do forklifts.
About the only difference is tractor counterweights (ballast) are removable and you can tailor the ballasting for the job at hand.

 

[AGGIE00]

Well, bigger tractors require ballast too.
Since you mention industrial equipment...take a closer look next time. They have huge permanet counterweights built right into them (big thick castings). So do forklifts.
About the only difference is tractor counterweights (ballast) are removable and you can tailor the ballasting for the job at hand.

I know that, but I always thought is was for capacity and not to keep from damaging axles. We run 420d IT backhoes all day in 4x4 with as heavy of load as it will carry and never a damaged axle, even at 10k hours.

 

[Tractor King]

You don't have enough weight...I added ballast to both tires about 500 lbs plus a weight box about 600 lbs plus....you need at least 1000 lbs to take the weight off the front end.

 

[Muxster]

When the 3005 revision of the 790 came out, some said the front end was stronger. I looked at the parts list for the 790 and compared it with the 3005 and indeed the gears have different part numbers. Everything else has the same part number. I wonder if the 3005 gears could be put in the 790 front end.

 

[RoyJackson]

When the 3005 revision of the 790 came out, some said the front end was stronger. I looked at the parts list for the 790 and compared it with the 3005 and indeed the gears have different part numbers. Everything else has the same part number. I wonder if the 3005 gears could be put in the 790 front end.

Print out both parts lists and compare, PN by PN...to see what else has changed. Also, just because the PN changed doesn't mean there's a stronger component.
There may also be bore diameter or other machining differences too.

This would be a good question for your dealer to take to Deere engineering to find out what changed and why...before you bought any parts.