Scope: Replace front strut/shock absorber assembly on Fiat 55-60 / 60-90 / 79-90 / 80-90 / 90-90 / 100-90 tractors (typical telescopic hydraulic damper style used on these tractors). Steps below cover preparation, removal, replacement and reassembly, plus tools, how to use them, safety and common pitfalls. Consult the tractor’s workshop manual for any model-specific variations and exact torque figures.

Tools & consumables
- Hydraulic trolley jack or farm jack rated for axle load
- Heavy-duty axle stands or timber cribbing (2 pairs) — rated and stable
- Wheel chocks (heavy duty)
- Metric socket set (10–32 mm), deep sockets
- Combination wrenches (open/box)
- Breaker bar (for seized nuts)
- 1/2" or 3/8" impact gun (optional but speeds removal)
- Torque wrench (appropriate range for mounting bolts)
- Penetrating oil (PB Blaster, WD-40 Specialist)
- Hammer and drift / brass punch
- Pry bar
- Long screwdriver
- Rubber mallet
- Needle-nose pliers and snap ring pliers (if applicable)
- Wire brush and cleaning rags
- Anti-seize compound and thread locker (medium strength)
- Replacement parts: new strut/shock(s), new mounting bolts/nuts and washers (always replace hardware if corroded), new rubber bushings/mounts/dust covers/bump stops if worn
- Safety gear: safety glasses, gloves, steel-toe boots

Safety precautions (must-follow)
- Park on a level, hard surface. Engage parking brake, place wheel chocks on rear wheels.
- Never work under an unsupported axle. Use rated jack stands or timber cribbing under axle/frame.
- When removing any component that supports load (axle, control arm), fully support the load before removing bolts.
- When fitting coil-sprung strut assemblies: only use an approved spring compressor and follow its manufacturer instructions. If uncomfortable, have a shop do spring work.
- If using impact tools, wear hearing protection and eye protection.
- Dispose of old hydraulic dampers properly — they contain oil/pressurized gas.

Preparation
1. Park tractor on level ground, lower implements, shut off engine, remove key.
2. Chock rear wheels and ensure tractor is stable.
3. If working on both sides, replace one side at a time so tractor remains stable.
4. Clean area around the top and bottom strut mounts of dirt and grease to locate bolts.

Removal — general procedure
1. Raise and support
- Place a hydraulic jack under the front axle near the strut to take load off the strut. Raise just enough to remove wheel (if wheel removal needed) or to relieve load on strut.
- Support tractor securely on jack stands under the axle housing or chassis. Do not rely on jack only.
- If working without wheel removal: ensure steering lock and safe access.

2. Remove wheel (if applicable)
- Remove wheel nuts and wheel to expose strut lower mount. Cleaning wheel mounting faces helps reassembly.

3. Support axle/beam
- Place a secondary support (jack stand or block) under axle/beam close to strut lower mount to take load when you remove the strut lower bolt.

4. Disconnect ancillary items
- Disconnect brake hose/lines or cable brackets attached to the strut. Support brake components so hoses are not under tension.
- Remove any linkages attached to the strut (anti-roll/sway bar link, radius rod brackets, steering drag link if interfering). Label parts if needed.

5. Remove bottom mounting bolt
- Spray penetrating oil on lower bolt and let soak 10–15 minutes if rusty.
- Use breaker bar or impact to remove lower mounting nut/bolt. Hold one side with wrench while turning the other.
- If bolt is seized, apply heat (careful, avoid hoses and rubber) or cut with grinder; replace with new bolt.

6. Remove top retainers
- Locate upper mount (cab mount or chassis bracket). Remove upper nuts/bolts. Depending on model, top may be inside engine bay or under cab — clean first so you don’t drop nuts into recesses.
- Keep track of any spacers, washers or bushings orientation.

7. Remove strut
- Slide lower end out of mount or drop assembly down. If stuck, use pry bar; protect paints and sensors.
- Remove old rubber bushings and retainers. Inspect top mount and surrounding structure for cracks or damage.

Inspection & parts replacement
- Replace the strut with a matching specification unit for the model (dampening rate, length, and mounting style). On some tractors, left and right struts are identical; on others they may be directional — check part number.
- Always install new rubber bushings and washers. Replace any corroded bolts, nuts and washers with new grade hardware.
- Replace dust boots and bump stops if damaged. Replace top mount bearings (if fitted) when worn.
- If the original strut is gas-filled or shows oil leakage, always replace (do not attempt to rebuild on-field).

Installation — general procedure
1. Pre-fit new bushings/washers
- Fit new rubber bushes, sleeves and dust cover onto the new strut in the same order/orientation as removed.
- Lightly grease sleeves with silicone or assembly grease (do not use petroleum grease on rubber unless approved).

2. Position strut
- Lift new strut into position. Insert upper mount first and loosely fit upper nuts/bolts finger-tight just to hold it.
- Align lower mount and insert lower bolt. Some tractors require aligning by moving axle slightly; use the jack to carefully lift/lower to line up holes. Never pry the axle into a dangerous position.

3. Tighten hardware
- With tractor resting on ground or weight supported appropriately (some manufacturers require final torque with normal ride height), torque lower and upper mounting bolts to workshop manual specs. If manual not available: typical heavy-duties range 80–200 Nm depending on bolt size — use correct spec where possible.
- Apply medium-strength threadlocker to bolts if the manual calls for it; otherwise use anti-seize on threads if reusing bolts (preferred to replace bolts).
- Reconnect any brackets, brake hoses, sway links, steering links and ensure no binding.

4. Reinstall wheel and lower tractor
- Fit wheel, tighten wheel nuts to spec.
- Lower tractor from jack stands; torque wheel nuts to final spec with tractor on ground.

5. Final checks
- Check alignment of steering if any steering links were disturbed. Inspect for leaks, rubbing or interference.
- Road/test at low speed. Listen for clunks and re-check torque after first few hours of operation.

How each tool is used (brief)
- Hydraulic jack: lift axle/tractor for safe removal; always place jack stands before working under load.
- Jack stands/cribbing: permanently support tractor while you work.
- Breaker bar: apply steady torque to free seized bolts.
- Impact gun: quickly loosen/tighten fasteners (use care), good for corroded bolts — finish with torque wrench.
- Torque wrench: final correct torque on mounting bolts to prevent loosening or overstressing bolts.
- Penetrating oil: soak stuck bolts before attempting removal.
- Spring compressor: only if strut uses coil spring — compress spring safely to remove top nut. Follow compressor instructions strictly.
- Pry bar/hammer/drift: release stuck mounts, tap out bolts after penetrating oil.

Common pitfalls & how to avoid them
- Removing both sides at once: can destabilize tractor. Replace one side at a time.
- Not supporting axle before removing bolt: axle can drop causing injury and damage.
- Seized bolts: use penetrating oil and heat; don’t apply excessive force that twists mount or breaks bracket. Replace bolts if damaged.
- Reusing old rubber bushings: leads to noise and premature wear. Always fit new bushings if worn.
- Incorrect orientation of strut or bushings: keep track of sequence and orientation when removing.
- Not torqueing fasteners to spec: leads to loosening or stressed components. Use torque wrench.
- Mixing left/right if directional dampers: install correct side if manufacturer specifies.
- Compressed spring hazards: never use makeshift compressors; use approved spring compressors and follow instructions.
- Forgetting to check associated items: worn top mounts, ball joints, tie rod ends, sway bar links can cause premature failure of new strut.

Replacement parts checklist
- New strut/shock absorber assembly (model-specific)
- Upper mount bushings / bearings (if fitted)
- Lower bushings/sleeves and washers
- Dust boot and bump stop
- Appropriate grade bolts/nuts/washers (replace corroded or stretched bolts)
- Thread locker and anti-seize

Final note
Follow the tractor workshop manual for exact torque values, mounting sequences and model-specific details. If top mounts are hard to access or springs are present and you lack the right compressor, get the job done at a properly equipped shop.

End of procedure.
rteeqp73

Short, direct workshop-style guide for hydraulic-clutch repair on Fiat 55–60 / 60–90 / 79–90 / 80–90 / 90–90 / 100–90 tractors — written for a beginner mechanic. Includes theory, every component explained, common failures, tools/parts, step-by-step procedures (master & slave cylinder service, full clutch replacement), bleeding, adjustment, and testing. Follow manufacturer torque specs where indicated.

Safety first
- Work on a level surface. Chock wheels. Use jack stands or heavy stands rated for the tractor weight. Never rely on a jack alone.
- Remove ignition key and disconnect battery if you will be working near the starter or electrical parts.
- Brake fluid corrodes paint and rubber and is harmful to skin/eyes — wear gloves, eye protection, and have rags handy.
- Support the transmission with a transmission jack or heavy floor jack and blocks before unbolting it from the engine.
- Keep dirt out of hydraulic components. Contaminated fluid ruins seals.

Theory — how the hydraulic clutch works (simple)
- Analogy: a hydraulic clutch is like two syringes connected by a tube. Pressing one syringe (pedal → master cylinder) pushes fluid, which pushes the other syringe (slave cylinder), which moves a lever that releases the clutch.
- Hydraulic principle: Pascal’s law — pressure applied to a confined fluid transmits equally. The master cylinder converts pedal travel/force to hydraulic pressure; the slave converts that pressure back into linear motion to disengage the clutch.
- Purpose: to disengage the engine from the transmission so gears can be changed without grinding, and to allow the tractor to be stopped with the engine still running.

Main components — detailed descriptions and function
1. Clutch pedal
- The operator input. Pivot-mounted on the floor or linkage box. Pushes the master-cylinder pushrod.

2. Master cylinder (MC)
- A small cylinder with a reservoir on top. Inside is a piston and seals. Pedal push moves the piston, pressurizing brake-type fluid and forcing it down the hydraulic line.
- Reservoir keeps fluid and allows for expansion; has a cap with vent/diaphragm.

3. Hydraulic line (hard steel line + flexible hose)
- Steel pipe from MC to engine bay then flexible hose to the slave. Carries fluid under pressure. Contains fittings (banjo, flare, or compression) and possibly a check valve or union.
- Banjo bolts use copper crush washers — always replace washers when disturbed.

4. Slave / release cylinder (external or internal/concentric)
- Converts fluid pressure into mechanical displacement. On these Fiat tractors it is usually an external cylinder that pushes a clutch release lever/fork; some variants may use internal release bearings. Inside are a piston and seals.
- Has bleed nipple/bleeder screw for removing air and a port for hose or rigid line.

5. Clutch release lever / fork
- A lever mounted on a pivot that the slave pushes on; the other end pushes the release bearing against the pressure plate fingers.

6. Release bearing (throw-out bearing)
- Bearing that contacts the pressure-plate diaphragm/fingers; slides on the input shaft hub. Allows the rotating pressure plate to be displaced by the stationary release fork.

7. Pressure plate
- Bolts to the flywheel and clamps the clutch disc to the flywheel. Diaphragm or springs apply clamping force.

8. Clutch disc (friction plate)
- Splined to the transmission input shaft. Friction material on both faces. Its thickness and rivet condition determine wear.

9. Flywheel
- Bolts to crankshaft. Mating surface for clutch disc. May be machined or replaced if scored or heat-streaked.

10. Pilot bearing/bushing
- Supports the transmission input shaft in the crank nose. Usually a small bearing or bronze bushing.

11. Reservoir cap & vent, seals, crush washers
- Small items but crucial: seals keep fluid in; crush washers seal banjo bolts.

Symptoms that indicate hydraulic clutch repair is needed
- Soft or spongy pedal, pedal sinks to the floor — likely air in system or MC/slave seal failure.
- Pedal does not return or is very stiff — sticky piston, bent linkage, or return spring problem.
- Loss of fluid in reservoir — visible leak at fittings, hose, master or slave cylinder.
- Clutch slipping under load despite pedal up — worn clutch disc or insufficient clamp force (warped flywheel/pressure plate).
- Difficulty shifting gears or grinding — clutch not fully disengaging (air in system, worn disc, bent linkage).
- Leaking fluid on transmission bellhousing, under tractor, or at hose fittings.
- Pulling or grabbing when clutch engages — glazed disc, oil contamination, or uneven pressure plate.

What can go wrong (failure modes)
- Master cylinder seal failure — internal or external leak, loss of pressure, air ingress.
- Slave cylinder seal/piston failure — external leak or seized piston.
- Corroded/hardened flexible hose or blocked steel line — leaks or flow restriction.
- Leaky banjo/flare fittings — lose fluid, air enters system.
- Air in the hydraulic circuit — spongy pedal and incomplete disengage.
- Contaminated fluid (water, dirt) — accelerated seal failure, corrosion.
- Worn clutch disc, damaged pressure plate, faulty release bearing — mechanical clutch failure even if hydraulics are fine.
- Damaged pilot bearing — transmission input shaft misalignment.
- Flywheel heat damage — reduces clamp force and causes slip.

Tools and consumables you'll need
- Basic hand tools: wrenches, sockets (metric), breaker bar, torque wrench.
- Screwdrivers, pliers.
- Line wrenches (flare-nut wrenches) for hydraulic fittings.
- Drain pan, rags, brake fluid or hydraulic fluid as specified by manual.
- Replacement seals / rebuild kit for MC and slave OR new MC/slave assemblies.
- New copper crush washers for banjo bolts.
- Clutch alignment tool (splined bar) if doing clutch replacement.
- Transmission jack or heavy-duty floor jack + stands.
- Bench vise, honing tool (if rebuilding cylinder bore) — only if you’re rebuilding pistons and bores.
- Bleeding kit — plastic hose and clear bottle, bleed wrench; vacuum bleeder or pressure bleeder optional.
- Torque values chart/manual (OEM torque specs). If not available, have a torque wrench and consult manual or dealer for critical bolts like flywheel bolts.

Fluids and parts
- Use the hydraulic fluid specified in your tractor manual. Many tractors use DOT 3 or DOT 4 brake fluid in clutch systems; some use hydraulic oil. If unsure, check the decal/manual. NEVER mix DOT fluid with hydraulic/mineral oil; it ruins seals if wrong.
- Buy new seals, copper washers, and replacement cylinders if leaking. If the clutch assembly is worn, buy new clutch disk, pressure plate, pilot bearing, release bearing.

Diagnosis checklist (quick)
1. Inspect reservoir fluid level and color. Dark, filthy fluid → contamination.
2. Look for external leaks at master, lines, fittings, and slave.
3. Press pedal: is there pressure? Does pedal feel spongy? Does fluid level drop while pressing?
4. Remove filler cap and have assistant press pedal to look for bubbles — bubbles mean air entering or internal MC leak.
5. Check operation of slave/rod movement (with engine off) by having assistant press pedal and watching slave movement.
6. If hydraulic parts are dry and pedals spongy, rebuild/replace master or slave.

Procedure A — Master cylinder service or replacement (bench and in-situ)
When: fluid leaks at master cylinder, internal failure (pedal sinks), or visible damage.

1. Prepare
- Park tractor, secure, chock wheels. Clean area around reservoir to prevent contamination entering when opened.
- Place drain pan under MC and along the line.

2. Remove master cylinder (if replacing) or prepare for bench bleed (if reusing)
- Disconnect hydraulic line using line wrench. Plug or cap the line to limit fluid loss/air ingress.
- Unbolt MC from pedal box/ firewall. Carefully remove. Keep upright to avoid spilling.

3. Repair vs Replace
- Rebuild kits exist: replace internal seals, cups, and O-rings. If bore of MC is scored or pitted, replace entire MC.
- If rebuilding, inspect bore for corrosion. Hone gently only if you know how; otherwise replace.

4. Bench-bleed master cylinder (essential)
- Secure MC in a vise upright.
- Fill reservoir with recommended fluid.
- Attach short clear tubing from MC outlet ports back into the reservoir (loops that flow back).
- Slowly push piston with a suitable rod until no bubbles rise. Repeat until no air escapes.
- Leave the tubing attached and filled; this keeps air out during installation.

5. Reinstall
- Mount MC to pedal box and torque bolts to spec.
- Reconnect rigid line with new crush washers if banjo style; tighten snugly but to spec.
- Reconnect reservoir and top up.

6. If you replaced the MC, you must bleed the system after installation (see bleed procedure below).

Procedure B — Slave cylinder replacement or rebuild
When: visible leak at slave, piston sticks, slave not moving.

1. External inspection & removal
- Clean area around slave cylinder and bleed screw.
- Place drip pan and plug hose to avoid pouring fluid onto painted surfaces.
- Loosen and remove the hydraulic line at the slave (use line wrench); cap or plug line to prevent contamination.
- Support the release lever or fork and unbolt slave mounting bolts.
- Remove the slave cylinder assembly.

2. Rebuild vs Replace
- Rebuild kits include piston seal, dust seal, spring. If bore is scored/corroded or piston is pitted, replace the cylinder.
- If you rebuild, inspect bores, hone lightly if required, install new seals, lubricate seals lightly with correct fluid, and bench-bleed the slave by pushing piston slowly in and out until no bubbles.

3. Reinstall
- Refit slave to the release lever/pivot. Ensure pivot/bushings are in good condition. Fit new banjo/ crush washers where applicable.
- Tighten mounting bolts to spec. Connect hydraulic line using new washers and torque to spec.

Procedure C — Full clutch removal and replacement (if hydraulic components are OK but clutch is worn/damaged)
When: slipping, burning smell, visible wear or heat spots, rivets near disc edge, heavy chattering.

1. Preparation
- Drain hydraulic fluid if the slave or bellhousing will be contaminated. Cap lines.
- Mark transmission/engine positions for reassembly alignment if needed.
- Remove PTO shaft, prop shaft or drive couplings if needed. Disconnect gear linkages, speedometer cable, and wiring harnesses attached to gearbox.
- Remove starter motor for access to bellhousing bolts if necessary.

2. Support the gearbox
- Use a transmission jack under the gearbox. Remove gearbox mounting bolts, front and rear supports as required.

3. Separate gearbox from engine
- Unbolt bell housing bolts while supporting tranny. Carefully move gearbox rearwards until it clears the clutch pressure plate and input shaft. Do not allow gearbox to hang by speedometer cable or lines.

4. Remove clutch assembly
- Unbolt pressure plate in a criss-cross pattern a few turns at a time to relieve stress evenly. Remove pressure plate and clutch disc.
- Inspect flywheel surface for heat streaks, cracks, scoring. Machine or replace if necessary.
- Remove and inspect pilot bearing/bushing. Replace if worn or noisy.
- Inspect release bearing and release fork — replace bearings every clutch job.

5. Fit new clutch components
- Clean flywheel and crankshaft bolt holes. Use thread locker if specified.
- Use clutch alignment tool and center the disc on the crank pilot. Fit the new pressure plate over the disc and screw bolts finger-tight.
- Tighten pressure plate bolts gradually in a star pattern to the manufacturer torque.
- If flywheel was removed, torque flywheel bolts to spec and in sequence.

6. Reassemble gearbox to engine
- Slide gearbox into place ensuring input shaft engages splines without forcing. Use alignment dowels and ensure gearbox mating faces are clean.
- Reinstall gearbox bolts, starter, linkages, PTO, etc., torquing to spec.

7. Reconnect hydraulic components
- Reconnect slave, lines, and refill reservoir if drained.

Bleeding the hydraulic system (step-by-step)
- Objective: remove all air from the hydraulic line so pressure is transmitted reliably.

Method 1: Two-person pump bleed (common and simple)
1. Fill master reservoir with correct fluid. Keep cap loosely on but not sealed to allow venting.
2. Have one person sit in the tractor and operate the clutch pedal; the other works at the slave bleeder.
3. Open the slave bleeder 1/4 turn. Assistant presses pedal slowly to the floor and holds it down. Close bleeder. Assistant slowly lets pedal back up. Repeat. Each cycle will push bubbles out.
4. Keep reservoir topped up—do not let it run dry.
5. Repeat until no bubbles come out and pedal feels firm with proper travel.

Method 2: Vacuum or pressure bleeder (faster, cleaner)
- Connect a vacuum pump to the slave bleeder and draw until no bubbles, or use a pressure bleeder on the master reservoir as per device instructions.
- Always keep master reservoir filled while bleeding.

Notes:
- If system had major air or you rebuilt MC, bench-bleed first (as above), then do pedal bleed.
- Bleed until pedal is firm and clutch fully disengages.
- Check for leaks during and after bleeding. Tighten fittings as necessary.

Adjustment and settings (post-bleed)
- Pedal free play: set as per manual. Typical range for tractors: small free play (a few mm) where pedal moves slightly before engagement begins. Too much free play can cause incomplete disengagement; too little can cause drag and premature wear.
- Release bearing clearance: check by feel or as per manual; there should be slight clearance when clutch is engaged.
- Check that pressure plate bolts are torqued evenly. Re-check after a few hours of use.

Testing procedure
1. Start engine and with parking brake on, depress clutch and select a gear (preferably low gear). Release clutch gradually — check for smooth engagement, no grinding.
2. Test for slipping: with implement off and engine at moderate rpm, drive in a low gear and accelerate. If engine revs increase without proportional ground speed, slipping remains.
3. Test for full disengagement: with engine running, depress clutch fully and shift up/down through gears — shifts should be smooth.
4. Check for hydraulics: pedal should be firm and consistent. No fluid loss, no leaks at fittings.

Troubleshooting common scenarios
- Pedal spongy after bleeding: likely remaining air — re-bleed. Check for leaks allowing air entry (worn MC or cracked hose).
- Pedal sinks slowly to floor when held under pressure: internal master-cylinder leak — rebuild or replace MC.
- Fluid loss at banjo bolt — replace copper crush washers and torque properly.
- Slave piston stuck or binding: remove, inspect bore and piston; if pitted or scored, replace cylinder.
- Clutch slips with firm pedal and no leaks: mechanical wear — clutch disc, pressure plate, or flywheel issue; replace clutch assembly and resurface or replace flywheel.
- Grinding when shifting: clutch not disengaging fully — check hydraulic pressure, bleed, or check for bent linkage or worn pilot bearing.

Maintenance tips and best practices
- Replace hydraulic fluid periodically (old/dark fluid holds moisture and causes corrosion).
- Replace crush washers whenever hose/banjo is disturbed.
- Always bench-bleed a rebuilt/new master cylinder before installing.
- Keep work area and parts clean; dirt in the system ruins seals.
- Replace the release bearing and pilot bearing whenever the clutch is serviced — cheap insurance.
- Replace both master and slave if one has failed and the other is old (they usually wear together).

Common sizes and torque notes (general guidance)
- Do not rely on these for final torque values — consult the specific Fiat service manual for exact torque settings.
- Pressure plate bolts: often 30–50 Nm (tighten in star pattern).
- Flywheel bolts: usually higher torque — often 70–120 Nm and sometimes an angle torque spec.
- Banjo bolts: 20–30 Nm typically.
- Slave cylinder mounting bolts: 25–50 Nm.
- If unsure, contact dealer or reference the specific workshop manual for your model.

Final checklist before returning tractor to work
- No leaks at master/slave/lines. Reservoir full and capped.
- Pedal travel and free play set correctly.
- Clutch release bearing replaced or inspected.
- Flywheel/pressure plate clamped to spec.
- Test drive with light loads, then re-torque bolts after the first few hours of operation where recommended.

Quick analogies wrap-up
- Hydraulic clutch = two syringes connected by a tube; one pushes, the other moves the fork.
- Clutch assembly = sandwich (flywheel & pressure plate are slices of bread; clutch disc is the filling that gets squeezed).
- Air in system = spongy balloon between the syringes preventing good force transfer.

This guide covers diagnosis and repair steps for the hydraulic clutch system components and full clutch replacement. For exact part numbers, dimensions, and torque values use the official Fiat workshop manual for your specific tractor model.
rteeqp73