Newbie JD 790 Question

[bstiles]

Hey Everyone! I just took delivery of my new JD 790 (300 FEL and 5' Box Blade) and I have a question. A friend told me that I'd have problems running a rotary cutter or post hole digger with this tractor because the "transmission clutch in the rear-end" isn't heavy enough to take the abuse. I consider this person to be very knowledgeable (certainly moreso than myself) but I can't see any forum posts about this sort of thing. I would appreciate any advice you could give. Thanks, Bryan.

 

[beenthere]

Welcome to the forum.

Find out what your "friend" bases his comment on, as it seems a bit fabricated to me. Curious as to what a "transmission clutch in the rear-end" is that he is referring to per your quote. If "it" will not take the abuse, then Deere would let you know up front that you cannot run a PHD or RC behind it. If it breaks, Deere will cover it under warranty, so I'd suggest you talk to your Deere dealer to clarify what you cannot use your JD 790 for.

 

[pruntyc]

I hope the thousands of 790 owners don't find out they can't use their rotary cutters, as I'm sure just about all of them do. Where does people get these ideas, they don't have any idea what they are talking about. The 790 in made by Yanmar, and they don't make a junk tractor, they have made many thousands of them. /forums/images/graemlins/grin.gif

 

[bstiles]

Thanks for the replies. I suspected that this was the case. I have been using my 790 for a couple of days now to dig post holes for the new fence and the tractor seems to handle it fine. The only problem I'm having is that the auger isn't digging too well.

 

[Michigan_Mike]

Bryan,
Well John Deere shows two rotary cutters for the 790.
They also show two Rotary mowers, but no post-hole diggers.
But that could be beacuse they don't sell posthole diggers.
I'm pretty much a newbie too, but it would seem to me that if the attachment is designed for the horsepower of the 790, you shouln't have any trouble.
I run a 6 foot rotary cutter off of my 790 with no toruble.
Regards,
Mike

 

[rockyridgefarm]

I am pretty sure that the clutch he is referring to is the tpo clutch. And while you should not get too worried, you really need to be sure that you are operating it correctly. It actually is very possible to tear it up with a rotary cutter or post hole digger.

Make sure that you have read the owners manual carefully.

Make sure that you have the proper length driveline - too long can be deadly!

Make sure that you have proper driveline protection. Shear bolts that are in spec or a slip clutch that is properly torqued.

Does the 790 have an overrunning clutch? I don't know?

 

[mountain_man]

400+ hours on my 2000 JD790. Plenty of heavy use with a 5' rotary cutter (Howse) and PHD (Leinbach 12" & 9" auger). Broke quite a few PHD shear pins in our "Rocky" mountain soil too.

</font><font color="blue" class="small">( Does the 790 have an overrunning clutch? )</font> Yup!

 

[RoyJackson]

All excellent replies!

Now, when you do start a cutter, you don't want to be at PTO speed (about 2600 RPM). Make sure you're around 1200 or so RPM (and prepare to blip the throttle if the tractor starts to stall). Let the cutter spin up for 8-10 seconds...then increase to PTO speed smoothly.

I would imagine dumping the clutch at rated PTO speed would not be good for the tractor or cutter gearbox.

Now, I run a 5' cutter behind a 790. This is through brush that is tall and thick. No problems here...

 

[Joe1]

This series of JD tractors and it's predecessors have been around a long time. They are extremely reliable, and with proper maintenance and some common sense usage, they can handle a PHD or a Rotary cutter without a problem.

However, anyting misused can be broken. Maybe your friend is too hard on his equipment.