Why this repair is needed — plain language
- Function: On MF 255/265/270/275/290 tractors the “torque sensor” (often called the draft/torque tube sensor or torsion sensor) is the mechanical device that senses twisting (torque) in the transmission/torque tube caused by the load on the implement. That twist is converted into a small movement that tells the draft control valve how much to raise/lower the 3‑point hitch so the implement keeps a constant working depth or load.
- Analogy: think of the sensor as a spring scale built into the drivetrain. When the implement pulls harder, the “spring” twists a little; that twist moves a control rod that tells the hydraulic valve “lift a bit” or “hold steady.”
- Symptoms of failure: hitch won’t hold depth, hitch drifts up or down, inconsistent draft control, tractor stalls or lugs under load, visible play or looseness in the torque tube area, hydraulic leaks from the sensor housing, or busted seals. If the sensor is wrong or stuck, the control valve gets wrong signals and the hitch will misbehave.
- Why replace rather than adjust: wear, internal broken torsion element, corroded/seized linkage, or damaged seals often require replacement rather than adjustment. Replacing restores the correct mechanical sensing and prevents hydraulic control problems and implement damage.

How the system works — simplified
- Mechanical sensing: a torsion bar or torque tube element in the sensor twists under driveline torque. The sensor’s internal parts convert that twist into a linear movement of a control rod/lever.
- Signal to hydraulic servo: the linear movement either moves a small hydraulic spool or moves a linkage that positions the draft control valve’s servo. That changes hydraulic pressure to the lift ram to raise/lower the hitch.
- Linkage path: engine/transmission output → torque tube → sensor housing (torsion bar) → sensor output rod → draft control lever/hydraulic valve.
- Return & adjustment: a spring and adjustable nut/shim pack set the sensor neutral/preload and allow calibration so the system is centered at no-load.
- Leaks/sealing: the sensor is sealed to keep gearbox oil in and contaminants out. Worn seals cause oil loss and can allow dirt in, which accelerates wear.

Major components you’ll see and what each does
- Sensor housing (cast aluminum/steel): mounts to the transmission/torque tube and contains the internal torsion element.
- Torsion element / torque tube / torsion bar (internal): the twisting member that actually bends when load is applied.
- Output shaft / rod: converts the twist into a small linear/rotational movement that connects to the draft control linkage/rod.
- Linkage bracket and clevis/pin: connection point between sensor output and the draft control lever or top link.
- Neutral/preload nut and locknut (or shim stack): set the zero point (how much twist = zero signal) and preload on the torsion element.
- Seals / O‑rings / gaskets: keep gearbox oil and hydraulic fluid sealed; common failure items.
- Mounting bolts/plate and spacers/shims: hold housing location and alignment; shims set engagement/preload and alignment.
- Return spring (if fitted): returns the control rod to neutral.
- Optional dust cover/boot: protects linkage and seal area from dirt.
- Associated hydraulic draft control valve & rods (not inside sensor): the downstream device that acts on hydraulic rams based on sensor movement.

Tools, parts, safety gear you need
- Tools: set of metric sockets and wrenches, torque wrench, screwdrivers, punch & hammer (for drift pins), pliers, snap‑ring pliers if applicable, breaker bar, penetrating oil, container for draining oil, soft mallet, pry bar, grease, thread locker (medium strength), safety stands/jack, rags, wire brush.
- Replacement parts: the replacement torque sensor assembly (OEM or exact aftermarket fit), new seals/O‑rings/gaskets, new mounting bolts if corroded, new cotter pins/pins, any shims specified, replacement linkage clevis if chewed.
- Fluids/consumables: transmission/hydraulic oil (to top up), solvent/cleaner, anti‑seize, grease.
- Safety gear: eye protection, gloves, steel‑toe boots, suitable clothes. Hydraulic oil is slippery and contains contaminants — avoid skin contact.

Preparations — before you start
1. Work on level ground. Park tractor, set parking brake, block wheels.
2. Lower 3‑point hitch and PTO implements to rest on ground (reduces load and makes linkages slack).
3. Kill engine and remove key. Disconnect battery negative to prevent accidental starts and electrical shorts while working near linkages.
4. If the rear end is heavy or you need to drop axle housings, use a jack and stands rated for the load. Many jobs can be done with the tractor on the ground if the hitch is lowered, but support the tractor if you must raise it.
5. Have rags and a drip tray ready — expect some oil loss.

Step‑by‑step replacement procedure (beginner‑friendly, assume sensor mounted on rear transmission/torque tube)
Note: tractors vary slightly; this is a procedure for common MF 200‑series layouts. Follow your tractor’s workshop manual for exact pictures, bolt sizes, and torque specs. If a manual is not available, use the torque ranges at the end.

1. Mark positions and take photos
- Before removal, mark the relative position of the sensor housing to the transmission and mark the linkage position and any shims or spacer stacks. Take clear photos from multiple angles. This makes reassembly alignment easier.

2. Remove exterior guards and covers
- Remove any rear covers, PTO guards, or linkage shrouds that block access to the sensor and linkage.

3. Disconnect linkage
- Remove the clevis pin or retaining pin that connects the sensor output rod/arm to the draft control lever/top link. Keep any washers/shims in order. If cotter pins are used, straighten and replace with new ones later.
- Note: if linkage is corroded, spray penetrating oil and let sit before removing pins.

4. Drain or contain oil leakage
- Place drain pan under the sensor mount. Expect transmission oil to seep or run out when you remove the sensor. If the sensor has an oil passage, you may be able to plug lines; otherwise, be ready to catch oil.

5. Remove sensor mounting bolts
- Loosen and remove the bolts holding the sensor housing to the transmission/torque tube. Keep bolts in order and note any shims/spacers. Some designs have a locating dowel—support the housing so it doesn’t drop as bolts come out.
- If the housing is stuck from corrosion, use penetrating oil and a soft mallet to break it loose (don’t damage mating faces).

6. Carefully extract the sensor
- Pull the sensor assembly straight out. Expect the torsion element to pull free and any internal shim stack or preload nut may come with it. Be careful not to damage the seal bore or the transmission mating surface.
- Inspect for metal flakes, heavy scoring, or a broken torsion element. Those indicate internal failure.

7. Inspect mating surfaces and parts
- Clean mating faces, bolt holes, and the output rod area on the transmission. Remove old gasket material with a plastic scraper; avoid gouging surfaces.
- Check the transmission side for damage to the input shaft or spline (if applicable). Check the torque tube for cracks and the linkage eye/bushings for wear.

8. Install new seals or O‑rings on replacement sensor
- If your replacement sensor did not come presealed, fit new seals and O‑rings. Lightly coat seals with proper oil/grease and press into grooves evenly—do not twist seals.

9. Fit the replacement sensor into position
- Align the replacement sensor with the transmission mating face and any locating dowel. Gently slide it in straight — do not force or angle it. Ensure any shims/spacer stacks are in the same order and position as removed.
- Hand‑start the mounting bolts, then tighten them in a star pattern evenly to bring the housing home.

10. Torque bolts to spec
- Use a torque wrench. If you don’t have the MF manual, use typical torque values for the bolt size (common sizes: M10, M12). See the “approximate torque values” below; when possible confirm with factory manual.
- Apply medium thread locker on bolts if the original used it.

11. Reconnect linkage and set neutral/preload
- Reattach the clevis/pin between sensor output and draft control lever. Reinstall new cotter pins if used.
- Adjust the sensor neutral/preload nut or shim stack to the positional marks you made earlier (or follow the manual adjustment method):
- With hitch lowered and no load, set the sensor nut so the control rod is in neutral (no hydraulic movement). Small incremental turns and lock the nut when correct. The objective is to restore the original no‑load alignment and ensure the sensor spring has the correct preload.
- If you have no marks, a common method: center the control lever, then set the sensor nut until there is a slight freeplay movement before the draft control begins to actuate. This is delicate — small changes make a big difference.

12. Refill and top up fluids
- Refill any leaked transmission/hydraulic oil to the correct level per the fill marks. Make sure the tractor is level when checking levels.
- Replace any filters if recommended.

13. Bleed/prime hydraulics if necessary
- Some installations will not need bleeding; others may trap air. Cycle the 3‑point hitch up/down several times, with engine running at low idle, to let the system settle and purge air. Recheck fluid level after cycling.

14. Test under low load
- Start the tractor, idle up, and test hitch movement with no external load. Check for leak at sensor seals and mounting.
- With the tractor stationary and engine at operating speed, slowly apply a small load (or lower an implement into the soil lightly) and watch how the draft control responds. Confirm the hitch holds position under load and returns correctly.
- Re‑check linkage, bolts, and fluid level after 10–20 minutes of operation. Retorque bolts if recommended.

15. Final checks
- Ensure all guards are reinstalled, clevis pins secured, and cotter pins replaced.
- After 8–10 hours of use, recheck bolt torque and hydraulic levels.

Common things that can go wrong and troubleshooting
- Continued hitch drift after replacement:
- Sensor incorrectly preloaded/neutral; re‑adjust neutral nut/shims.
- Draft control valve internal wear or sticking; sensor swap won’t fix valve problems.
- Worn lift rams leaking internally — rams not holding position.
- Leaks at sensor after new install:
- Bad/new seals not seated, mating surface scratched, or wrong seal type. Remove and inspect.
- Sensor assembly rotates or housing moves:
- Mounting bolts not torqued enough; shims missing; use proper torque and shims.
- Excessive play in linkage:
- Worn clevis, bushings, or pins; replace worn linkage items.
- Oil contamination and wear:
- Metal flakes or heavy scoring indicate internal breakage — inspect gearbox and torque tube for damage.
- No sensor movement but linkage attached:
- Internal torsion element broken; sensor will need replacement again or different unit.
- Engine stalls under load with seemingly correct sensor:
- Could be an unrelated engine/fuel issue or hydraulic pump not delivering; check pump and filters.

Torque/bolt‑tightening guidance (if you don’t have the manual)
- Always reference factory manual when possible. If not available, use these safe approximate torque ranges (metric bolts, dry threads). Use a torque wrench.
- M8 bolt = 20–30 N·m (15–22 ft·lb)
- M10 bolt = 40–60 N·m (30–45 ft·lb)
- M12 bolt = 70–90 N·m (50–66 ft·lb)
- M14 bolt = 100–130 N·m (74–96 ft·lb)
- Tighten evenly in a star/cross pattern to avoid distorting housings.

Final safety notes (do not skip)
- Hydraulic oil is under pressure—do not loosen fittings while engine is running.
- Support the tractor whenever you lift or remove heavy components; don’t rely on jacks alone.
- Replace cotter pins and safety clips removed — don’t reuse old lightly‑stressed pins.
- Clean everything — grit and dirt in the sensor area shortens life.

Closing — quick checklist before you finish
- Sensor installed and torqued
- Linkage reconnected and secured (new cotter pins)
- Neutral/preload set per marks/manual
- No leaks and correct oil levels
- Function test with controlled load
- Recheck bolts and oil after initial running hours

This covers the why, how it works, what can go wrong, and a beginner‑level step‑by‑step replacement workflow. Use the workshop manual for your MF model for exact part numbers, diagrams, and factory torque specs.
rteeqp73

Massey Ferguson 255 Tractor - WMSOHIO Sells at auction April 8, 2021 - Tiffin, OH.

Massey Ferguson 255 - Overview This is my Massey 255, I have decided to part with it even though I love this machine. I grew up with Massey Ferguson tractors and ...

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