3206 Diff Lock Question

[Oak]

Jsoluna, why did they do that? I don't use my diff-lock at all and your saying if I use the brakes it will engage the lock? That scares me. I didn't look under mine yet but I did read in the 3206 manual about what carhopper posted. I looked at the 3205 manual and I didn't see where it said what the 3206 does. I was thinking that if you hit the brake pedal that it would release the lock. Thanks for the pics and explanation.

[jsoluna]

For what it's worth, my 3205s manual doesn't say squat about brake/difflock either. The good thing is, in your case, that you only use the brake sparingly, and I'm assuming while the tractor is at rest - which is how the difflock should be properly engaged. What should happen is that if the tractor does not move from that spot, when you release the brake, differential lock will NOT be engaged.


Kinda difficult to explain without pics again so here we go:

Whole rearend teardown on a difflock aluminum case rear of a 3200 Series:


Difflock housing - notice the center 4 holes....these are where the pins in the difflock collar slide into to "lock" the two axles together. See the wear marks?



Difflock collar disengaged (natural postion, kept from engaging by a spring between the two pieces):


Difflock collar engaged (pins in collar line up with holes in housing thus locking the two axles together.)
Unit will remain in difflock as long as continuous motion is applied (the force keeps the pins engaged in the housing)



Disengaging difflock requires:

1. Force no longer being applied to collar/housing (stop the tractor)
2. Difflock pedal released
3. (In some cases) reverse motion applied slightly to relieve force on pins
4. Continue direction of travel


It kinda upsets me that whoever was in charge of the documentation for these tractors didn't deem it necessary to provide adequate information to the customer about how this setup should work. Even the dealerships weren't properly advised. That's a large reason difflock gets a bad rap on the 3k Series machines.

[Sam Mac]

Justin

You did an awesome job in illustrating how the diff lock functions.

It would seem that it should have been designed to be engaged separately rather than by applying the brake and that they should have properly described it’s use in the owners manual.

[Oak]

Justin, that is great info. I can see now why the lock pins will break if the wheels are spinning and someone locks the rear. That is a poor design by Cub. I guess it was too much money to put a warning decal on the machine. I think these are great mowing machines but I would be afraid to pull a plow with one. What does one expect for a $7000 machine.

[jsoluna]

To be fair, the rearend in these tractors is strong enough for its application. It may not be over-engineered, but it is certainly adequate. Lots of 3K Series owners push these tractors beyond their supposed limitations and the machines perform well.

If the difflock is used properly, it will last for the life of the tractor. The instances I've seen grenaded rearends on the 3K Series machines were due to improper use. Is it a more complicated setup? Sure. But I wouldn't hesitate to use the difflock function, or to use the 3K Series in general as a garden tractor should be - whether that be pulling a plow or mowing grass.

I agree that connecting the brake and difflock operations was a shortsighted design, though. If they had done more field research with these tractors I think they would have realized that, and that it was important to inform the owner of the proper way to use the difflock function.

[Oak]

Okay, I had to cut grass tonight and was thinking about this issue. After I was done I used the blower to clean all the junk off of it and got the looking and took some pics. I sat in the seat and pushed the brake as far in and set the parking brake as seen in the first pic. You can see the yellow arm pulling on the brake rod near the frame and the diff lock spring has slack in it as I push up on it. The middle pic is both pedals at rest and the spring has the same slack in it, notice the same brake rod arm is now pointing up. The last pic is the diff lock engaged and the spring has tension on it and I could also hear something making contact inside the rear.

This tractor has less then 75 hours on it and is like new. I'm wondering if something is binding inside the brake shaft/diff lock shaft causing the problem you guys are having.....I'm just wanting to know so I don't tear mine up.

[jsoluna]

From your scribe marks in the pic it looks like yours do indeed move independently. It pulls on the brake rod, but does not move anything outboard from that point. Is that true, or am I just not seeing that the scribe mark has moved in the first pic? Let me take a closer look at mine and see why mine move together......

And in your pics, there's two bushings that isolate the difflock bracket/pedal assembly from the brake rod. I haven't had my brackets installed in a while, let me grab the parts and see whats going on here.

[Oak]

Justin, yes they do move independently and there is also a plastic bushing on the diff-lock lever. I wonder if that bushing is gone and the two shafts are siezed on yours and carhoppers?

[jsoluna]

I'm definitely learning from this as well, thanks for sticking with it, Oak!

When you depress the brake pedal....does the rod move all the way from one side of the frame to the other, all the way at the end where the difflock pedal mounts?

My difflock bracket/pedal assembly isn't seized...its not even installed now. (Swapped in a rear from a 3184 last winter). I'm willing to bet that mine is the same as yours though. Although the shaft is connected to the braking, the difflock mechanism is NOT engaged because the bracket for it simply rides on those nylon bearings.

In our 3205's setup, the brake rod just serves as a pivot point for the difflock pedal operation.

We may be safe to brake on our units without engaging difflock. We still need to figure out why carhopper's 3206 DOES engage the difflock. Under the parts lookup, the difflock pedal and bracketry is identical. He should have the cast iron rear though, unlike our 3205s.

[jsoluna]

Oh, and nice pics of your 3205. It's so clean!!!! I'm so used to seeing the 900hrs of abuse that mine has gone through