No Pin to Wear Loose: The MF1025 IH Cub Cadet Steering Knuckle Development
Every turn of your Cub Cadet's steering wheel rides on one small through pin. MF1025 replaces it with a solid Torx joint. No pin to wear loose. The drag arm is one solid machined piece, not two pieces welded together. And we took out the bend, too.
International Harvester built the Cub Cadet to be kept running by its owner: simple parts, ordinary tools, honest work. More than sixty years on, these tractors are still mowing, plowing and pulling. But one part keeps coming back to the bench: the left-hand steering knuckle. This is how we fixed it, from a notebook sketch in 2019 to finished sets on our bench in 2026.
- No pin to wear loose. A solid, wrench-tight T80 Torx joint locks the drag arm to the knuckle.
- One solid drag arm. Machined from one piece of steel. No weld between arm and hub.
- No bend. The bent knuckle's weak spot is gone, too.
- Both sides. Left- and right-hand knuckles plus the drag arm, in one set.
- Bolts right on. Same axle, same layout IH designed.
Fits Cub Cadet models 70, 71, 72, 73, 100, 102, 104, 105, 106, 107, 122, 123, 124, 125, 126, 127 and 147.
MEISTERFABRIK is an independent manufacturer. We are not affiliated with or endorsed by International Harvester, Case IH or Cub Cadet. Brand names and OEM part numbers are used only to identify the tractors and parts this kit fits.
The trouble with the original
Every turn goes through one part
Each front wheel rides on a steering knuckle: an L-shaped piece of steel. The bottom of the L is the spindle the wheel turns on. The top pivots in the cast-iron axle.
The left knuckle does the steering. Turn the wheel, and the drag link pushes the drag arm, which turns the left knuckle. The tie rod then carries that motion across to the right side. The drag arm itself is two pieces, an arm and a hub, welded together. A through pin holds it to the knuckle. The tractor's own weight keeps the knuckles seated.
So every turn you make goes through that one pin, and through one bent part. That is why the left side is the one that fails.
Weak spot number one: the through pin
The pin goes straight through the drag arm and the knuckle. Every push and pull from the steering lands on that one small pin and the thin walls of the holes around it. Back and forth, thousands of times. The pin wears, the holes wear, slop creeps into the steering, and in the end the pin can shear.
Weak spot number two: the welded drag arm
The original drag arm is built from two pieces welded together. Every steering push passes through that weld, right next to the pin.
Weak spot number three: the bend
The spindle swings about the curved section with every bump and every turn. That is where it can break.
We found both, pin first, when we tested the original on the computer, the way engineers do. It matched what owners see in the field.
A new replacement part is made the same way, with the same bend and the same pin. It can fail the same way again.
The fix: MF1025
We kept everything IH got right: the same axle, the same layout, the same drag link and tie rod. We changed only what was weak, and the biggest change is the joint.
A solid, wrench-tight T80 Torx joint locks the drag arm to the knuckle. The steering force is spread all the way around the joint instead of landing on one small pin.
The original drag arm is an arm and a hub welded together. Ours is machined from one solid piece of steel, so there is no weld in the steering path of the drag arm.
Each knuckle is built from two pieces, an upright and a spindle, pressed together and welded. There is no curved section left to flex and crack.
We moved up from the A36 of generation 1 to a tougher structural steel (grade in the numbers box below), machined to close tolerance for steering without slop. Black oxide finish that you can paint over.
The drag arm sits 10° forward of the axle centreline, just like the original IH part. Left and right knuckles come together, so both wheels match.
The set replaces the original left-hand knuckle, right-hand knuckle and drag arm (OEM 759-3004-0637, 759-3006-0637 and 759-3120).
Seven years in the making
The original: a through pin
It started in April 2019 with an old knuckle on the floor and a notebook. Every radius and diameter came off worn, sixty-year-old parts. The first thing on our list was the through pin.
2019: generation 1, a custom Torx
Our first version was a small run of 18 left-hand knuckles. It brought:
- A36 structural steel.
- A thicker section through the bend.
- The big one: our own custom Torx joint in place of the through pin.
- A drag arm machined from one solid piece of steel, not two pieces welded together.
- A shim to ease the steering load.
It still kept the original L shape, so we heated the bar and bent it in the vise.
What we got wrong
The steel was strong enough. But the bend still flexed. And we had the drag arm angle wrong. We set ours straight along the axle centreline. The original sits about 10° forward of it.
Owners told us so, plainly. A shortened drag link got them by for a while, but a band-aid is not a fix. Their feedback, including requests for a right-hand knuckle, shaped everything that came next.
2025: generation 2, a T80 Torx
From generation 1 to generation 2, here is what changed, and what we kept:
- Torx: from our custom Torx to a T80 Torx joint.
- Two-part knuckle: the bend is gone. The knuckle is now an upright and a spindle, pressed together and welded.
- Steel: from A36 to a tougher structural steel (grades in the numbers box below).
- Drag arm angle: advanced 10° forward of the axle centreline to match the original IH geometry. This was the big lesson from generation 1.
- Finish: the knuckles and arms now get a black oxide treatment, a classic dark finish. Generation 1 did not have it.
- Kept: the drag arm, still one solid machined piece, carried forward from generation 1.
The first test pieces for the T80 joint came off the mill in May 2025.
Why T80? Generation 1 used a custom Torx shape that only we could make. MF1025 uses a standard T80 profile instead, because we design for repair: a standard shape keeps the joint fixable and serviceable for years to come, the way IH built its tractors to be kept running.
By August we had prototypes on the bench: a straight spindle and a separate upper section, joined instead of bent.
We built the field-test sets in our new workshop. Then we cut one complete left-hand assembly apart on purpose, to find anything hidden, and improved our welding from what we learned. The first full set passed every check after welding before it went to black oxide and final assembly.
2026: in production
In spring 2026 we moved from single sets to batches: bar stock sawn, milled and turned into knuckles, spindles and drag arms.
Tested on the computer, the way engineers do
Before cutting steel, we loaded models of the original knuckle and of MF1025 on the computer and gave both exactly the same test: 500 lb pushing up along the spindle, with the upright held fast at the kingpin bore. Same push, same supports, for all four pictures below. The computer shows two things: how far each spot moves, and how close the steel comes to its limit.
The 500 lb is a bearing load, the push the wheel puts on the spindle, the kind of load that comes from the weight of the tractor and whatever is hung on it. We set it deliberately high, as an extreme test well beyond everyday use; the loads a knuckle sees in normal work are far lower.
How far it moves
In a movement plot the colours run from blue, where the steel barely moves, to red, where it moves most. On both knuckles the most movement is at the very tip of the spindle, the point farthest from the support. The movement is far too small to see, so the computer draws it bigger: about 26 times for the original and about 70 times for MF1025. Because the stretch is different, don't judge the two pictures by eye. Go by the numbers.
The original's spindle tip moves 0.037 in. From the bend outwards, the spindle swings like a gate on a hinge, and the bend is the hinge. MF1025's tip moves about a hundredth of an inch, 0.0129 in, roughly the thickness of three sheets of paper. That is about 65% less movement; the original moves about 2.9 times as far. In plain words: the spindle stays put, and your wheel stays where you set it.
How close it comes to the limit
The safety factor is how many times this load the steel could take before it starts to bend for good and stops springing back. A 2 means it could take twice the load. A 1 means it is right at the limit. Below 1, the load is already more than that spot can take, so it bends and stays bent.
In this extreme 500 lb test, the original's weakest spot, at 0.88, would start to bend for good at roughly 440 lb, less than the test load. MF1025's weakest spot, at 1.24, could take roughly 620 lb first. Rough figures from the model.
Red and orange mean near or past the limit. Deep blue means plenty of margin: the scale stops at 3, so blue means 3 or more.
Here is the headline for every Cub Cadet owner. Under this extreme 500 lb test, the inside of the original's bend, right where the spindle curves into the upright, drops to a safety factor of 0.88. The model says the steel there goes past its limit and begins to yield: not snap on the spot, but take a permanent set. Under the same test, MF1025 still has margin. And the bend the model flags is the very spot where the original in the second photo at the top of this story broke. That is why we took the bend out.
MF1025's lowest point, on the lower upright just above the spindle housing, is 1.24, so it still springs back, and nearly all the rest of the part sits at the top of the scale. Its weakest spot has about 40% more margin than the original's weakest spot. That comes from two changes working together: no bend, and a tougher steel (S355J2 in MF1025; the original was modelled with AISI 1045 as a stand-in, because the exact IH material is not on record). These are computer models, and 1.24 means margin under this load, not a part that cannot be broken. Where the original starts to take a set, MF1025 still springs back.
The other trouble spot on the original was around the pin, and the first photo up top shows an original broken right there.
MF1025 answers both. With no pin, there is nothing small to wear and shear. With no bend, there is no hinge.
- Steering (drag link) load: 375 lbf, about 1,668 N, at the drag arm.
- Based on a 655 lb tractor, 40/60 front/rear weight split, plus 168 lb of IH front weights.
- Wheel bearing load on the spindle: 500 lbf (about 2,224 N). An extreme test value, well above normal tractor and attachment weight.
- IH original, as reverse-engineered by MEISTERFABRIK (model 202004200005, study "Applied Steering Loads (-Pin Type Variation-)"): held at the upright/kingpin bore, 500 lbf up along the spindle. Material approximated with AISI 1045. Resultant displacement (URES): largest 0.037 in (about 0.94 mm) at the spindle tip, smallest 1.53e-07 in. Drawn about 26× (26.36×) larger than life.
- IH original, same study: factor of safety (criterion Automatic) ranges 0.885 to 3. Lowest, 0.885, at the inside of the spindle bend where it joins the upright. Below 1 means the model predicts yielding (permanent bending) there, not instant fracture.
- MF1025 left knuckle (model 202505291235), same 500 lbf and constraints as the original rerun: held at the upright/kingpin bore, 500 lbf up along the spindle. Resultant displacement (URES): largest 0.0129 in (about 0.33 mm) at the spindle tip, smallest 5.39e-07 in. Drawn 69.7× larger than life.
- MF1025 left knuckle (model 202505291235), S355J2, same 500 lbf and constraints: factor of safety (criterion Automatic) ranges 1.24 to 3. Lowest, 1.24, at the lower upright near the spindle joint; nearly all the rest of the part is at about 3.
- Lowest factor of safety, same load and constraints: MF1025 1.24 vs IH original 0.885, about 40% more margin (1.24 ÷ 0.885 = 1.40). Materials differ: S355J2 for MF1025, AISI 1045 as an approximation of the original.
- Same load, same plot type, same units: 0.0129 in vs 0.037 in, about 65% less movement (the original moves about 2.9 times as much). The displacement plots show movement, not stress.
- Drag arm angle, measured on our CAD models in plan view against the axle centreline: IH original 9.6°, generation 1 0°, MF1025 10.0°.
- Steel: generation 1 used ASTM A36 (standard minimum yield about 250 MPa). MF1025 uses EN 10025-2 S355J2 (standard minimum yield about 355 MPa, impact tested at −20 °C). These are the standard values for the grades, not test results on our parts.
What you get
- 1 × Left-hand steering knuckle assembly with Torx joint. Replaces 759-3004-0637.
- 1 × Right-hand steering knuckle assembly. Replaces 759-3006-0637.
- 1 × Drag link arm with Torx joint. Replaces 759-3120.
- 1 × Rigid connection link arm.
- 3 × Hex head cap screw.
- 1 × Black oxide 18-8 stainless steel hex head screw.
- 4 × Flat washer.
- 1 × Black oxide steel oversized washer.
The knuckles and arms are machined from S355J2 steel and black oxide treated, for a classic dark finish. The oversized washer and the 18-8 stainless hex head screw are black oxide too. One set per tractor.
Fitting it
Like the original, this set is meant to go on in your own shop. Our installation drawing lays it out in seven plain steps:
- Grease. Apply multi-purpose lithium EP grease, NLGI #2, liberally to the steering knuckle arm thrust surface and the bottom of the axle ends.
- Right-hand knuckle in. Insert the right-hand steering knuckle in its bore in the axle.
- Secure it. Fasten the right-hand knuckle with the cap screw and flat washer.
- Left-hand knuckle in. Insert the left-hand steering knuckle in its bore and position the drag link arm on it.
- Secure the arm. Fasten the drag link arm and knuckle together with the cap screw.
- Tie rod. Install the tie rod.
- Wheels and toe-in. Install the front wheels and check the toe-in adjustment.
What your money buys
New original parts for the same three pieces, the left knuckle assembly, the right knuckle assembly and the drag arm, cost $505.97 at PartsTree.com. That is about 5,030 SEK, before shipping and import. MF1025 is 5,176 SEK for the drag arm and both knuckle assemblies, with the washer and cap screws included. About 145 SEK more than new original parts, before you pay to get those parts to Sweden.
- 759-3004-0637 Knuckle Assembly, LH: $192.99
- 759-3006-0637 Knuckle Assembly, RH: $186.99
- 759-3120 Steering Arm Assembly (now 959-3120): $125.99
- Total: $505.97, about 5,030 SEK at 9.9446 SEK per USD (ECB reference rate, 23 October 2026). Shipping and import to Sweden not included.
Prices checked on PartsTree.com on 25 October 2026. Prices change. Click any part to check today's price yourself.
So the price is close. The difference is what you get for it. A new original part is made the same way, with the same through pin and the same bend. The steel is the smallest part of the MF1025 price. You are paying for experience and practice.
- The pin is gone. The joint is the heart of the steering. Getting from a through pin to a custom Torx in 2019, and on to the T80 Torx in MF1025, is the most valuable thing we did, and it took real practice to get right.
- One solid machined drag arm. Where the original arm was two pieces welded together, ours has been machined from one solid piece of steel since generation 1 in 2019.
- No bend. A two-part knuckle, upright and spindle pressed together and welded, with no bent section to flex.
- Tougher steel, dark finish. S355J2 structural steel, with black oxide on the knuckles and arms.
- Seven years of work. From a notebook sketch in April 2019, through generation 1, to batch production in 2026.
- Mistakes already made, and fixed. Our first 18 knuckles taught us the true drag arm angle: 10° forward of the axle centreline, as IH built it. You get the corrected design, not the first try.
- Made in our own workshop in Skövde. We mill, turn, weld and finish every part ourselves. We cut a finished assembly apart just to check our welds.
- Every set traceable. Each one carries a lot number back to its batch.
- Real people behind it. Questions on fit or installation go straight to the people who built it: sales@meisterfabrik.se.
No gimmicks. Nothing you can't inspect. Just a better-built part that fits the tractor as it was built, and that you can keep up yourself.
Keep it working
These tractors were built to be kept in service by their owners. MF1025 is built the same way: simple, rugged, and easy to look after. Fit it once, and put your front axle back to work for another generation.
Get the MF1025 Steering Knuckle Set
Over to you
How do you keep your Cub Cadet steering true: repair, replace, or your own fix? Tell us in the comments. Owners shaped generation 2, and you'll shape what we build next.