Summary (what this is and why): The transmission solenoid pack (electro‑hydraulic valve assembly) controls hydraulic flow used to engage gears/clutches or a shuttle in a Massey‑Ferguson MF35 equipped with electro‑hydraulic controls. If solenoids fail, you’ll get no engagement, slipping, delayed shifts, or erratic operation. Think of the solenoid pack as an electrical gatekeeper: electricity tells tiny plungers to open or close hydraulic passages, directing oil where it must go — like flipping electrically controlled faucets that route hydraulic “water” to clutches and actuators.

If your MF35 is an original early model it may not have an electronic solenoid pack unless retrofitted. Confirm the machine actually has a solenoid pack before starting.

What you’ll need
- Service manual / parts diagram for your exact tractor (essential for torque specs, part numbers, schematics).
- Tools: metric socket set, torque wrench, screwdrivers, pliers, Allen keys, multimeter, insulated test leads, small prybar, pick set, soft mallet.
- Fluids/consumables: appropriate tractor hydraulic/transmission oil, clean rags, replacement O‑rings/seals (kit), gasket sealer (if required), threadlocker (if specified), replacement solenoid pack or individual solenoids.
- Safety: gloves, eye protection, jack/stands or blocks, drip tray, container for used oil, rags, shop vacuum for spills.
- Optional: vacuum pump for bleeding, bench power supply (12 V) for coil bench test.

Component-by-component (what each part is and how it works)
- Solenoid coil: an electrical coil that creates a magnetic field when energized. The magnetic field pulls the plunger. Analogy: the coil is the electromagnet that closes an electric gate.
- Plunger / armature: ferrous rod that moves inside the coil. Movement opens/closes or shifts the spool valve.
- Spool valve (valve body): cylindrical valve that routes pressurized oil to different outlets depending on plunger/spool position. Think of it as a multi‑port plumbing valve that can be shifted to connect different pipes.
- Valve body housing / manifold: metal block with drilled oil passages, ports for supply, return, and work circuits, mounting surfaces, and bolt holes.
- O‑rings / seals: small rubber rings that seal ports and the plunger/spool ends. Prevent fluid bypass. Worn seals = leaks and loss of hydraulic pressure.
- Electrical connector / wiring harness: supplies +12V and ground or signal to each solenoid. Includes connector pins and possibly a protective loom.
- Mounting hardware: bolts, studs, washers that secure the pack to the transmission/housing.
- Pressure switch / sensors (if fitted): tell the controller or indicator lights about oil pressure or engagement status.
- Return and feed hoses/pipes/fittings: bring oil to/from the valve body.
- Reservoir/filter: not part of the pack but essential; dirty oil causes solenoid sticking and wear.

Theory of operation (simple)
- Hydraulic pump draws oil from the reservoir and supplies pressurized oil to the valve body.
- When the tractor’s controller or switch energizes a solenoid, the plunger moves, shifting the internal spool.
- The spool opens a path for pressurized oil to move to a clutch or actuator, engaging a gear/shuttle or operating a clutch. When de‑energized, springs return the spool to neutral.
- If coils don’t energize or spools stick, hydraulic pressure is not routed and the function fails.

Common failure modes (what can go wrong)
- Electrical: broken wires, corroded connector pins, blown fuse, bad ground, failed coil (open or shorted), wrong voltage.
- Mechanical: stuck plunger/spool due to varnish, sludge, rust, or metal particles; worn or torn O‑rings causing internal bypass and pressure loss; broken springs.
- Hydraulic: contaminated oil (metal, water, varnish), clogged filter, low oil level or incorrect oil viscosity, collapsed hose.
- Installation: wrong parts, reversed connectors, loose bolts causing leaks, incorrect torques causing distortion, pinched seals.
- Symptoms: no shift, slow or slipping engagement, intermittent operation, fluid leaks at pack, overheating, burnt smell.

Step-by-step replacement (beginner-friendly)
Prep and diagnostics (do these before tearing things apart)
1. Confirm symptoms: describe exactly what doesn't work (no engagement, slipping, intermittent). Note when it happens (cold/warm).
2. Safety first: park on level ground, engage parking brake, chock wheels, stop engine, remove key. Support raised parts securely.
3. Disconnect battery negative terminal to avoid accidental energizing.
4. Locate the solenoid pack using the manual/parts diagram. Identify connectors and hydraulic lines. Take photos of current routing and connector positions — label wires with tape if needed.
5. Electrical test:
- With battery connected (or bench supply), use the multimeter to check for supply voltage at the solenoid connector when the tractor control is used (key on or switch actuated). If there’s no supply, the problem could be upstream (switch, fuse, relay, controller).
- Measure coil resistance: disconnect connector and measure across coil pins. Typical solenoid resistances vary widely; consult manual. An open circuit -> bad coil. A short to ground -> bad coil/short. If you don’t have specs, compare coils to each other — a big difference suggests a bad coil.
6. If electrical supply is good and coils seem OK but functions still fail, suspect hydraulic contamination or leaking seals in the valve body. Look for oil leaks or foam.

Removal
7. Relieve hydraulic pressure: with engine off, cycle manual controls to relieve trapped pressure, or follow manufacturer procedure. Use rags and catch pan: hydraulic oil will leak when lines are disconnected.
8. Place drain pan under valve body. Loosen and remove hydraulic lines one at a time, plug both ends to minimize contamination. Mark which line goes where.
9. Unplug electrical connector(s). Inspect connector pins; clean if corroded.
10. Remove mounting bolts securing the solenoid pack to the transmission/case. Support the pack as you remove final bolts — it can be heavy.
11. Carefully remove the pack. Inspect mounting surface for damage, old gasket material, or debris. Scrape and clean mating surfaces gently.
12. Remove individual solenoids from the pack if replacing only the coils: typically screws hold coil bodies; plunger/spool assembly may be accessible. Keep parts in order.

Inspection and bench checks
13. Inspect O‑rings/seals and replace all. They’re cheap and necessary. Inspect spool bores for scoring or corrosion. Light corrosion may be cleaned; deep scoring requires replacement or remanufactured valve body.
14. Bench test solenoid coils by applying rated voltage briefly and watching for plunger movement (safe bench supply, short pulses only). Listen for a click. Don’t energize continuously for long periods on the bench to avoid overheating.
15. Clean valve bores with solvent and compressed air; use lint‑free cloths. DO NOT scratch the bores. Replace any damaged components.

Installation
16. Install new or rebuilt solenoid pack or solenoids: fit new seals/O‑rings (light film of hydraulic oil to aid seating), position pack on mounting face, and hand‑start bolts.
17. Torque mounting bolts to manufacturer spec (consult service manual). If manual unavailable, torque evenly and snug — do not overtighten; threading into transmission castings can be fragile.
18. Reconnect hydraulic lines to their original ports. Use new crush washers or seals if required. Tighten to spec.
19. Reconnect electrical connectors; ensure proper routing and strain relief. Replace damaged wiring. Reconnect battery negative.
20. Refill/verify hydraulic/transmission oil level. If you drained fluid, replace filter and fill with correct oil to proper level.

Bleeding and testing
21. Bleed air: many tractor systems bleed by cycling the controls and running the engine briefly. Follow manual: typically with engine idle, cycle gear/shuttle levers repeatedly to let oil work out air; check and top up fluid as needed.
22. Functional test: with wheels blocked, test operation at low engine RPM. Operate the control switches/lever and observe actuation. Listen for normal clicks of solenoids and watch for leaks.
23. Road/test: under light load, test full functionality. Monitor oil temperature, noises, and check for leaks.
24. Final check: after a few hours of operation, re‑check torque on mounting bolts and fluid level.

Troubleshooting tips and traps
- Contamination kills valves. If one solenoid failed and metal filings were present, flush the system and replace filter; consider full system flush.
- Never mix different oil types; follow MF spec.
- Pins seating: bent or corroded connector pins cause intermittent faults. Replace connector halves if corrosion present.
- If valve spools stick when cold but free when hot, suspect varnish / old oil. Consider ultrasonic cleaning or replacement.
- If new solenoids click but still no function, suspect internal hydraulic leak (worn spool bores) or pump pressure issue.
- Keep everything clean during reassembly — dirt on spool bores will reintroduce problems.

Safety & environmental notes
- Always relieve hydraulic pressure before disconnecting lines.
- Dispose of used oil and contaminated rags properly according to local regulations.
- Hot oil can cause burns; allow system to cool before working.
- If lifting tractor or components, use rated jacks/stands and support blocks.

When to call a pro / parts you may not be able to repair
- Deeply scored valve bores, cracked valve body or transmission housing.
- Complex electrical control modules or CAN/ECU faults beyond basic checks.
- If you lack the service manual, important torque/spec and sequence info may be missing — get the manual or professional help.

Final note (brief): Replace solenoids and seals, keep hydraulic oil clean, and diagnose electrical supply before replacing parts — often faults are wiring/fuse/connector related. Follow the manual for torque and bleeding sequences.
rteeqp73

Pt. 2/3: Splitting an Old Tractor - 1955 Massey Ferguson TO35 In this video, we split the engine from the transmission on our '55 TO35. Unfortunately, while doing some brush hogging last year, ...

Video Operator's Manual for Massey Ferguson 35 Tractor This video shows the basics of how to operate an MF35 tractor as well as identification of a lot of the components of the tractor.

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Safety first
1) Work on a cold engine, parking brake on, key off, disconnect the negative battery terminal if you will be working near wiring. Wear gloves and eye protection.

Quick orientation/theory (short)
2) Purpose of the PCV system: it evacuates combustion blow‑by (combustion gases that pass the piston rings) from the crankcase and routes them into the intake to be burned. The PCV valve is a one‑way, vacuum‑sensing metering valve that:
- Allows crankcase gases to be drawn into the intake under normal vacuum.
- Restricts or dampens flow during sudden throttle changes to prevent backflow and to maintain correct mixture.
- Prevents excessive crankcase pressure (which causes leaks, popped seals, oil weeping) and prevents fresh air from being drawn in uncontrolled (which upset mixture and idle).
On MF35 petrol engines the PCV is usually mounted in the valve/rocker cover and plumbed to the carburettor/intake with a hose. (Diesel MF35s commonly have a simple breather rather than a vacuum PCV.)

Step‑by‑step replacement (in order) with theory notes
3) Locate the PCV: it is typically a small valve in the valve/rocker cover with a hose to the carburettor or intake manifold. Theory note: location matters because it must tap crankcase pressure and see intake vacuum.

4) Inspect before removal:
- Check the hose for cracking or oil contamination.
- Check the valve for sludge, sticking, or if it rattles (shake test). Theory: a rattling internal check means the valve’s poppet is free to move; sludge/clog will prevent flow or stick it open/closed.
- If the engine is diesel, confirm whether you have a breather cap instead — diesel setups behave differently. (Brief confirmation; do not proceed if it’s a plain breather cap.)

5) Test (diagnostic theory before replacing):
- With engine idling, carefully remove the valve from the hose (leave it connected to the rocker cover opening if possible) or remove the hose and put your finger over the intake side: you should feel vacuum being drawn through the PCV opening. If there is little/no vacuum or excessive pressure (air pushing out), the system is faulty.
- Remove the PCV valve and shake it: a light rattle indicates the internal valve moves freely. If it’s stuck or clogged the valve won’t rattle and may be blocked. Theory: a working PCV will pass gases but prevent backflow; a stuck closed valve causes crankcase pressure; stuck open or perforated causes uncontrolled flow and mixture problems.

6) Remove the old PCV:
- Pull off the hose clamp, remove hose from valve, then withdraw the valve from the valve cover boss (it may be a push‑fit or threaded depending on aftermarket).
- Inspect the boss port for sludge. Theory: sludge indicates oil vapor condensation and may block passages; cleaning improves flow.

7) Clean the boss and hose or replace hose:
- Remove sludge with rag and solvent; ensure the port is clear. Replace brittle or oil‑saturated hoses. Theory: a new hose ensures no leaks and proper vacuum transfer; a clogged boss still restricts flow even with a new valve.

8) Fit the new PCV valve:
- Install the valve in the valve cover with correct orientation: the side marked “PCV” or the smaller end usually faces the intake (the one‑way/spring poppet orientation matters). Push or thread in per original fitment until secure.
- Reconnect hose and clamp. Theory: the valve’s internal spring/poppet must face so intake vacuum draws gases into the intake and the valve prevents reverse flow.

9) Start and check operation:
- Start engine, check for vacuum at the valve (engine should pull through the valve). Observe idle stability and listen for hissing/leaks. Inspect for oil leaks around valve and hose joints. Theory: restored regulated evacuation removes crankcase pressure and prevents oil weeping; correct metering avoids lean spikes or rough idle.

10) Road/test load and re‑inspect:
- Run under a few load conditions and recheck for smoking from breathers, oil leaks, and idle quality. Theory: under load blow‑by increases; a correctly functioning PCV should handle increased gases without excess pressure.

How the repair fixes common faults (concise)
11) If the symptom was oil leaks, oil on the air cleaner, or oil expelled from breather: A stuck or clogged PCV causes crankcase pressure to rise and forces oil out seals and gaskets. Replacing the PCV re‑establishes the one‑way vent and metering so blow‑by is drawn into the intake rather than escaping past seals.

12) If the symptom was rough idle, poor throttle response, white/blue smoke from intake, or fouled plugs: A stuck‑open or failed PCV can allow excessive crankcase vapors and oil into the intake, upsetting the air/fuel mixture and fouling plugs. Replacing the valve restores controlled flow and stops oil‑laden vapors from overloading the intake.

13) If the symptom was excessive crankcase vacuum or no vacuum: A failed (stuck closed) PCV prevents evacuation, raising pressure; a failed open/inoperative valve can remove too much vacuum or allow backflow. New valve corrects the metering function so vacuum varies appropriately and blow‑by is burned in the engine.

Final checks and maintenance
14) Replace hose every few years or when brittle. Clean valve cover boss when doing valve cover gasket service. Check PCV as part of routine tune‑ups. A cheap new PCV and hose replacement prevents gasket failure and oil leaks.

Done.
rteeqp73

Tools and supplies
- Basic hand tools: metric/AF socket set (deep and shallow), breaker bar, extension bars, ratchet.
- Torque wrench (range up to at least 150 ft·lb).
- Impact wrench (optional but helpful).
- Flywheel holding tool or flywheel lock (engine-specific hook/plate or a commercially made holder).
- Flywheel puller (if the flywheel is pressed on or stubborn).
- Clutch alignment tool (if MF35 has clutch/disc removal/reinstall).
- Pry bars, soft mallet.
- Screwdrivers, pliers, snap-ring pliers (as required).
- Jack, heavy-duty jack stands or support cribbing; wheel chocks.
- Drain pan and rags.
- Penetrating oil (e.g., PB Blaster), threadlocker (blue or red per factory spec), anti-seize (as applicable).
- New flywheel/flexplate bolts (recommended), pilot bearing (if fitted), rear main seal, clutch kit if worn.
- Cleaning solvent, gasket sealer, shop manual for torque specs and procedures.
- Safety gear: gloves, eye protection, steel-toe boots.

Safety precautions (must do)
1. Park tractor on level ground; set parking brake; chock wheels.
2. Disconnect battery negative.
3. Support tractor/transmission securely — do not rely on the jack alone. Use heavy jack stands or timbers under the frame/transmission housings.
4. Work with good lighting; keep hands/loose clothing away from potential pinch points.
5. Have an assistant when lifting heavy parts (flywheels are heavy).

Quick notes about terminology
- On an MF35 you’re generally dealing with the engine flywheel and clutch assembly (manual gearbox). Some people call it a “flexplate” but the MF35 uses a traditional flywheel. Steps below assume flywheel removal/inspection/replacement.

Step-by-step procedure

1) Preparation
- Disconnect battery and remove any nearby panels that block access to clutch housing/bellhousing.
- Drain gearbox oil if required by the removal procedure so you don’t spill when separating housings (check manual).
- Chock wheels and support tractor securely.

2) Remove driveline/controls
- Remove PTO shaft or driveshaft connections that prevent bellhousing removal.
- Disengage clutch linkage linkage/rod so the clutch assembly can be removed freely.

3) Access clutch and pressure plate
- Remove bolts around bellhousing/clutch cover and separate housing. Support the gearbox if it’s being moved — the gearbox is heavy.
- Remove clutch pressure plate bolts in a star pattern gradually to relieve pressure evenly. Remove pressure plate and clutch disc. Use clutch alignment tool to note orientation for reassembly.

4) Remove pilot bearing (if present)
- If replacing clutch or flywheel, remove and inspect the pilot bearing. Replace if noisy or worn.

5) Hold the crank / remove flywheel bolts
- Use a flywheel holding tool: bolt the holder to access holes on flywheel or engage the teeth so the crank cannot rotate. If you do not have a holder, use a heavy pry bar in the ring gear teeth with rags to protect teeth — but a proper tool is strongly recommended.
- Apply penetrating oil to bolts and let soak if bolts are rusty.
- Loosen flywheel bolts in a crisscross sequence a little at a time to avoid distorting the flywheel. Remove bolts and all washers/dowels. Note and mark flywheel orientation relative to crank if required by factory.

6) Remove the flywheel
- Pull the flywheel straight off the crank. If it’s tight, use a flywheel puller that bolts into the flywheel bolt holes or use even tapping with a soft-face mallet around the hub while protecting the teeth. Do not pry on the ring gear.
- Support the flywheel as you remove it — it’s heavy and will damage parts (and possibly you) if it falls.

7) Inspect / replace parts
- Inspect flywheel for cracks, hot spots, scoring, or warped surface. Check ring gear teeth for wear/loose fit. Check flywheel bolt threads and crank flange threads for damage.
- Check flywheel runout with a dial indicator across the friction surface; acceptable runout is small (refer to manual). If the friction surface is glazed or scored, resurface or replace flywheel.
- Replace pilot bearing and rear main seal while access is easy.
- Replace flywheel bolts with new bolts (recommended; many are torque-to-yield/stretch-type and should not be reused). Use correct grade bolts per service manual.

8) Reinstall flywheel
- Clean crank flange and flywheel mating surfaces thoroughly.
- If flywheel has a timing mark/orientation, line it up exactly with crank flange as per manual.
- Apply threadlocker if factory calls for it (or anti-seize where specified).
- Start all flywheel bolts by hand, then snug in a star/crisscross pattern.
- Torque bolts to factory specification using the correct sequence. If you don’t have the manual, obtain the exact MF35 engine spec — typical small tractor flywheel bolt torque is high (do not under-torque). Using an incorrect torque risks failure. (If you must use a number as a temporary guide, many similar engines use roughly 60–100 ft·lb range depending on bolt size — consult the manual before final torque.)
- After torquing to spec, some procedures call for a final angle-tightening or recheck after a few hours of operation; follow manual.

9) Reinstall clutch and bellhousing
- Install new or resurfaced pressure plate and clutch disc using the alignment tool. Torque pressure plate bolts gradually and evenly to spec.
- Reassemble bellhousing, reconnect clutch linkage, reinstall driveshaft/PTO components, refill gear oil if required.
- Reconnect battery.

10) Final checks
- Verify clutch engagement and pedal travel; adjust linkage per manual.
- Start engine and check for unusual noises, leaks, or vibration. Re-torque bolts if manual specifies a re-check.

How the main tools are used (short)
- Flywheel holding tool: bolts to the engine or engages ring gear to stop crank rotation while loosening/tightening bolts. Always keep the holder solidly anchored; do not rely on a screwdriver or thin pry bar.
- Flywheel puller: bolts into tapped holes in the flywheel and forces it off the crank flange evenly. Use to avoid hammering or damaging the crank flange.
- Torque wrench: final tightening to factory spec; use the proper range and read increments carefully.
- Clutch alignment tool: centers the clutch disc on the pilot bearing so pressure plate bolts go on without misalignment.

Common pitfalls and how to avoid them
- Reusing flywheel bolts: bolts can be torque-to-yield. Replace them. Reusing often causes failure.
- Not supporting heavy parts: gearbox/flywheel falling will cause severe injury and damage. Use stands and an assistant.
- Damaging ring gear teeth: don’t jam pry bars in teeth; use a proper holding tool.
- Incorrect torque: under-torqued bolts loosen and can shear; over-torqued bolts stretch and fail. Always use factory torque specs.
- Contaminating friction surfaces with oil/grease: clean surfaces and handle clutch facing and flywheel face with clean gloves.
- Not replacing pilot bearing/rear main seal when accessible: do them while it’s apart — saves rework.
- Improper flywheel orientation/dowel alignment: mark orientation before removal and reinstall exactly as found.
- Skipping runout check: warped flywheels cause vibrations and premature clutch wear.

Replacement parts typically required
- Flywheel bolts (recommended).
- Pilot bearing/bushing (if present).
- Rear main seal (recommended when flywheel is off).
- Clutch disc and pressure plate (if worn or when flywheel replaced/resurfaced).
- Ring gear (if teeth are damaged) or entire flywheel if cracked/warped.

Final note
Follow the Massey Ferguson MF35 service manual for exact bolt sizes, torque values and any engine-specific procedures. The above covers the full safe process and common traps for removing/servicing the flywheel (flexplate) and clutch area on an MF35.
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