[markat425]

I've been investigating what it would cost to install RWA on a 7720 if I buy one that doesn't have that option. I have recieved prices on a "planetary style" and a "cam-lobe" style. What is a cam-lobe style? Which is preferable? The price for the cam-lobe is twice what the planetary type is.
Educate me,, please....

Mark

 

[jd9600guru]

Re: 7720 RWA ?

planteary 4 wd came on earlier 20 series while the 1200cc cam lobe motors came along later.

Basically, the platenary style has a small hydraulic motor that drives a large set of planetary gears in the rear hub to provide 4wd power.

The cam lobe motor uses multiple pistons that ride over cam lobe ramps and have hi pressure oil applied to them on the down side of the cam, thus causing forward thrust that is transferred to the wheel. 9000 series are the same and even new combines use this type of motor although it is more refined now.

hope thsi helps,

jd

 

[markat425]

Re: 7720 RWA ?

Thanks jd,,
Are the cam lobe style noticably more powerful? Do these RWA systems have their own pump, or are they plumped into the hydro system?
I used to work for a guy that had a New Idea Uni-Harvester with the planetary RWA. When you would engage it, your speed would be cut in half, or so it seemed. Just wondered if they are all like that?


Mark

 

[riceman]

Re: 7720 RWA ?

Quote:Thanks jd,,
Are the cam lobe style noticably more powerful? Do these RWA systems have their own pump, or are they plumped into the hydro system?
I used to work for a guy that had a New Idea Uni-Harvester with the planetary RWA. When you would engage it, your speed would be cut in half, or so it seemed. Just wondered if they are all like that?


Mark

I can't speak for 7720's but on 9600's, STS, and just about any other color that runs a hog is like that. Its not quite half speed but close. In my combine it goes from 2nd gear at about 7.5 mph wide open to around 5.5 with the mudhog in gear. Still plenty fast to run in the mud.

 

[greentech]

Re: 7720 RWA ?

Both designs use existing hydrostatic flow, which is why the speed is cut down. All new 4wd systems are cam lobe now. I'd go that route. If you get a used kit make sure all the necessary parts are included, right down to the last fitting.

 

[markat425]

Re: 7720 RWA ?

Thanks Greentech... I'll do that...

If the machine I end up with has been switched to 30.5 x 32 rubber, what size tires should be run on the RWA? I wonder if Deere has chart to tell what sizes should be matched with the RWA tire size?


Mark

 

[8820titan2]

Re: 7720 RWA ?

We have 16.9X26's on both of our 8820's. Both have 30.5X32's.

 

[jd9600guru]

Re: 7720 RWA ?

You can also run 18.4-26's without any probelms.

I believe a 23.1-26 will get into the ladder or tailings elevator.

jd