Box Blade Sizing for Kubota L3901

FriendwithTractor · Jun 19, 2023

Hello Friends,

I have acquired a new to me L3901 that's already proved its worth with just the FEL.
My friend as I've discussed previously has just finished constructing a house and now needs help with the finishing dirtwork.
The ground is clay with rocks (specifically shale)

To get to the point, I'm trying to size a box blade for the L3901 that would be appropriate for grading what remains of his backyard and a decent slope. I'm also hoping to use this for leveling my own building pad, cutting trails and maintaining a driveway.

Advice would be appreciated. Thank you!

RjCorazza · Jun 19, 2023

I would think a 6' box blade would suit you well. If your clay and rock gets to be too much you can always raise the shanks a little or use every other one.

jeff9366 · Jun 19, 2023

As you know, there is no hydraulic down pressure applied to the Three Point Hitch. Therefore, the heaviest Box Blade weight per unit of Box Blade width will give best penetration and skiveing ability. For standard Box Blades this is usually around 80 pounds per foot of width. For Rollover Box Blades this is usually around 120 pound per foot of width.

You will appreciate a heavy Box Blade as counterbalance on the Three Point Hitch when doing Loader work.

SKIVE: to split or cut, as leather, into layers or slices. to shave, as hides.

deezler · Jun 19, 2023

6'. Cover the width of the tires plus an inch or two extra on each side. I dunno the width of a 3901 (what tires?) but if a 66" box blade covered it well, that would give you more ripping and pulling power.

TractorTech · Jun 19, 2023

Agree that a 6' would be the correct size. You want to be just wider than the rear tires too. This allows you to use them as your guide whole not being oversized for the tractor.

FriendwithTractor · Jun 19, 2023

deezler said:
6'. Cover the width of the tires plus an inch or two extra on each side. I dunno the width of a 3901 (what tires?) but if a 66" box blade covered it well, that would give you more ripping and pulling power.

Ag tires on front and rear, 4 wheel drive and diff lock available as well.
I should also mention that it's an HST.
Wheel base according to tractor data is 63.3 inches, but I haven't measured mine.

deezler · Jun 19, 2023

A 3901 probably has the guts to pull a 72" box blade. Plenty of power, but the tractor is a little light. Loaded tires would help. Keeping your FEL bucket loaded with a scoop of dirt helps also.

I had a 72" box blade on my Cub Cadet 7305 (30 HP) and it was a little too big. Very easy to anchor it with roots underground, or an overflowing load of soil, and get the tractor stuck. Had to raise the box blade up a lot to keep moving.

FriendwithTractor · Jun 19, 2023

jeff9366 said:
It is time to revise your tractor make and model in your T-B-N PROFILE.

~~Ford 1220~~

Noted and Adjusted.

deezler said:
A 3901 probably has the guts to pull a 72" box blade. Plenty of power, but the tractor is a little light. Loaded tires would help. Keeping your FEL bucket loaded with a scoop of dirt helps also.

I had a 72" box blade on my Cub Cadet 7305 (30 HP) and it was a little too big. Very easy to anchor it with roots underground, or an overflowing load of soil, and get the tractor stuck. Had to raise the box blade up a lot to keep moving.

Good to know, considering this is mountain ground, roots would be endemic. I was thinking of getting the rears filled anyway just to do FEL work.

TractorTech · Jun 19, 2023

FriendwithTractor said:
Ag tires on front and rear, 4 wheel drive and diff lock available as well.
I should also mention that it's an HST.
Wheel base according to tractor data is 63.3 inches, but I haven't measured mine.

Wheelbase is length from center of front axle to center of rear axle.
Overall width is 55", but of course that can be changed with rear wheel adjustments.

How wide is your loader bucket? Ideally, matching the bucket width makes operating easy, but again, there are other factors to consider on a box blade.
Also, the rear wheels on any FEL tractor should be adjusted to give you good stability.

FriendwithTractor · Jun 19, 2023

TractorTech said:
Wheelbase is length from center of front axle to center of rear axle

Thanking you, Then the width would be 55 inches according to tractor data.

scootr · Jun 19, 2023

Use the rear tire width outside to outside as your guide. Also consider whether you will be adding stability spacers.
I added 6" to the overall width of my Kubota. It made a big difference.
Go slow . Hitting rocks in clay with rippers is like a watchdog hitting the end of his chain

ROUSTABOUT · Jun 19, 2023

A little wider than your back tires. You want it to cover your tracks. Then as you make more passes, the tires will be on smoother bladed ground, blade will be on smoother ground, it all gets smoother. Plus, you don't want a blade too wide for a sided trailer. Even a 7' blade will need a deck over trailer. Most trailers with sides aren't 7' wide between the side rails.

jeff9366 · Jun 19, 2023

FriendwithTractor said:
I was thinking of getting the rears filled anyway just to do FEL work.

Research first. Pound-for-pound counterbalance on the Three Point Hitch is much more effective than liquid filled tires due to leverage, for FEL work.

With loaded R1/ag tires you will NOT be able to traverse your eventual lawn without rutting.

None of my three tractors have had loaded tires. For my tractor applications, a good decision. My Kubota L3560 is about 1,000 pounds heavier than your L3901, with the same width. My 60" width Rollover Box Blade weighs approximately 630 pounds. R4/industrial tire width is 62".

milkman636 · Jun 19, 2023

I have a very similar size and spec tractor. I found an old, heavy rhino 66" with a flip up scarifier bar that is a perfect match for my machine. I need to be in low range and throttled up to work with the teeth down and full box of dirt. I had a lighter 72" one previously that was less effective even though it was newer and shinier. Weight is your friend in a box blade.

FriendwithTractor · Jun 19, 2023

Thank you all for the advice. I'm new to dirt work not involving a shovel, so this is all very good information. I will measure the outside to outside rears tonight and take that going forward into my research.

jeff9366 · Jun 19, 2023

Read about your tractor's Manual Locking Differential in your Operator's Manual. You will often need to depress the MLD with your left-heel when doing Box Blade earth moving work.

RjCorazza · Jun 19, 2023

I have never heard of a limited slip differential in a tractor. I suspect they may exist in some more exotic application, but not in regular compact tractors.
All of the L series Kubota tractors I am familiar with have manual locking differentials.

Mtsoxfan · Jun 19, 2023

My New Holland has a lever to depress to get lock in. It's a pain in the ass, as it unlocks when torque is taken away from wheels. I find I'm just leaving my heel on it, which isn't comfortable at all...

ljjhouser · Jun 19, 2023

I agree with most others. 6' Land pride has the BB1272. I have a L4701 and I sometimes add a couple blocks to the weight. it weighs 400 pounds. EA makes one that is really nice and has more weight than the on I have. Your L3901 should do fine with 6'.

milkman636 · Jun 19, 2023

Mtsoxfan said:
My New Holland has a lever to depress to get lock in. It's a pain in the ass, as it unlocks when torque is taken away from wheels. I find I'm just leaving my heel on it, which isn't comfortable at all...

You may want to read a little on the diff lock in the owners manual of your tractor. There’s a high probability that it says to not drive around with your foot continuously pressing on the diff lock pedal.