Transmission mounts
Transmission mounts refers to the mounts and brackets that support the transmission or transaxle in the Pontiac Fiero.
The transmission mounts help secure the drivetrain to the rear cradle. Worn, broken, loose, or incorrect mounts can cause drivetrain movement, clunking, vibration, shifting problems, exhaust stress, axle issues, and other symptoms.
Overview
The Pontiac Fiero uses a transverse drivetrain mounted behind the passenger compartment.
The engine and transmission are supported by mounts attached to the rear cradle. These mounts control drivetrain movement while allowing some vibration isolation.
Transmission mount details can vary by engine, transmission type, model year, and previous repairs or swaps.
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Location
Image wanted: Photo showing Fiero transmission mounts installed on the rear cradle, preferably showing the mount, bracket, transmission case, and surrounding cradle area.
Transmission mounts are located in the rear engine compartment, between the transmission or transmission brackets and the rear cradle.
The exact location and arrangement depend on the installed transmission.
Factory transmission pages:
Function
Transmission mounts help hold the transmission in the correct position.
They also help control drivetrain movement caused by:
- Engine torque
- Acceleration
- Deceleration
- Shifting
- Clutch engagement
- Road vibration
- Drivetrain load changes
A mount must be strong enough to support and locate the drivetrain, but it also provides some isolation from vibration and harshness.
Relationship to engine mounts
Transmission mounts work together with the engine mounts.
A problem with one mount can place extra stress on the others. If only one mount is replaced while the others are worn, drivetrain movement may still remain.
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Relationship to the engine cradle
The transmission mounts attach the drivetrain to the rear cradle.
The rear cradle supports the engine, transmission, suspension links, and related hardware. Rust, damage, loose hardware, or previous repairs to the cradle can affect mount alignment and drivetrain position.
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Manual transmission mounts
Manual-transmission Fieros use mounts and brackets appropriate for the installed manual transaxle.
Factory manual transmissions include:
Mounts, brackets, and hardware should not be assumed to interchange between all manual transmissions without verification.
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Automatic transmission mounts
Automatic-equipped Fieros used the TH125 automatic.
Automatic transmission mounts and brackets are specific to the automatic drivetrain arrangement. They should not be assumed to interchange with manual transmission parts.
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Common problems
Common transmission mount problems include:
- Worn rubber
- Torn mount
- Broken mount
- Loose mounting bolts
- Missing hardware
- Incorrect mount
- Incorrect bracket
- Rusted cradle mounting area
- Previous incorrect repair
- Excessive drivetrain movement
- Vibration after mount replacement
- Engine-swap mount mismatch
Mount problems may be mistaken for clutch, transmission, suspension, or exhaust problems.
Symptoms
Possible symptoms of worn or damaged transmission mounts include:
- Clunking during acceleration or deceleration
- Clunk when shifting into gear
- Excessive drivetrain movement
- Vibration
- Harshness
- Exhaust contact or exhaust cracking
- Shift cable movement or binding
- Difficulty shifting
- Axle angle or axle stress concerns
- Engine or transmission appears to move excessively
- Noise when engaging the clutch
- Noise when selecting Drive or Reverse on automatic cars
These symptoms can also be caused by engine mounts, cradle problems, suspension parts, axles, exhaust contact, or transmission problems.
Drivetrain movement
Excessive drivetrain movement is a major clue when diagnosing mounts.
Movement may be most noticeable when:
- Starting from a stop
- Releasing the clutch
- Shifting gears
- Accelerating hard
- Letting off the throttle
- Selecting Drive or Reverse in an automatic car
A drivetrain that moves excessively can stress cables, hoses, wiring, exhaust parts, axles, and mounts.
Relationship to shifting problems
Transmission mount problems can affect shifting.
If the transmission moves under load, shift cables and linkage may move in ways that affect gear selection.
Possible mount-related shifting symptoms include:
- Shifter movement during acceleration
- Difficulty selecting gears under load
- Inconsistent shifting
- Shift cables binding or pulling
- Problem changes when engine torque changes
Mounts should be inspected when diagnosing shift cable or clutch complaints.
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Relationship to clutch problems
On manual-transmission Fieros, mount problems can be confused with clutch problems.
Worn mounts can cause clunking, drivetrain movement, vibration, or chatter-like symptoms during clutch engagement.
If a car chatters, clunks, or moves excessively when the clutch is released, inspect both the clutch system and the drivetrain mounts.
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Relationship to automatic transmission problems
On automatic-transmission Fieros, worn mounts can cause clunks when shifting between Park, Reverse, Neutral, and Drive.
This can be mistaken for internal automatic transmission trouble.
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Relationship to exhaust problems
Excessive drivetrain movement can stress the exhaust system.
Possible exhaust-related symptoms include:
- Exhaust contact with body or cradle
- Cracked exhaust parts
- Broken exhaust hangers
- Exhaust leaks
- Noise during acceleration or deceleration
Because the Fiero engine and transmission are mounted close to the exhaust system and rear cradle, mount condition should be checked when exhaust parts repeatedly crack or contact nearby components.
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Relationship to engine swaps
Transmission mounts are important in engine-swap cars.
Engine swaps may use custom mounts, modified brackets, different transmissions, different torque levels, or different drivetrain positions.
Swap-related mount concerns include:
- Mount strength
- Bracket design
- Cradle attachment points
- Transmission selection
- Axle alignment
- Exhaust clearance
- Shift cable routing
- Engine torque
- Vibration
- Serviceability
A mount setup that works for a stock engine may not be appropriate for a higher-torque swap.
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Inspection
Basic inspection checks include:
- Inspect transmission mounts for torn or separated rubber.
- Check for loose or missing bolts.
- Inspect transmission brackets.
- Inspect engine mounts at the same time.
- Inspect cradle mounting areas for rust or damage.
- Look for signs of drivetrain movement.
- Check whether the exhaust has been contacting nearby parts.
- Check shift cable routing and movement.
- Inspect axles and surrounding clearance.
- Verify that installed mounts match the transmission and engine combination.
A mount may look acceptable at rest but still allow excessive movement under load.
Diagnosis
When diagnosing possible transmission mount problems, consider:
- When the noise or movement occurs
- Whether it happens during acceleration
- Whether it happens during deceleration
- Whether it happens when shifting
- Whether it happens when selecting Drive or Reverse
- Whether the shifter moves during drivetrain load changes
- Whether the exhaust contacts anything
- Whether the mounts are original, aftermarket, custom, or previously repaired
Diagnosis should include both transmission mounts and engine mounts.
Replacement
Transmission mount replacement usually involves supporting the drivetrain safely, removing mount hardware, replacing the mount, and checking alignment and hardware condition.
General replacement considerations:
- Support the drivetrain correctly.
- Do not rely on a jack alone.
- Verify the correct mount before installation.
- Inspect brackets and cradle mounting points.
- Replace damaged hardware.
- Check engine mounts at the same time.
- Recheck drivetrain position after installation.
- Inspect shift cable routing and exhaust clearance after repair.
Service notes
When working on transmission mounts:
- Identify the installed transmission before ordering mounts.
- Do not assume manual and automatic mounts interchange.
- Do not assume all manual transmission mounts interchange.
- Inspect engine mounts at the same time.
- Inspect the rear cradle for rust or damage.
- Check for exhaust contact.
- Recheck shift cable movement after mount work.
- Be cautious with used mounts because original parts are decades old.
- On engine swaps, evaluate mount design and drivetrain movement carefully.
Notes
Transmission mounts are often overlooked during clutch, shifting, exhaust, or drivetrain-noise diagnosis.
A worn or broken mount can create symptoms that feel like a transmission problem even when the transmission itself is functioning normally.