The transmission mount is one of those parts you don't think about until it fails. Then suddenly your truck has horrible vibration, weird sounds, and shift issues. Here's the complete guide to trans mounts and what to choose.
What the trans mount does
The transmission mount:
- Supports the transmission weight
- Absorbs torque reaction from drivetrain
- Isolates engine/trans vibration from chassis
- Allows for minor flex during operation
When the mount fails:
- Severe vibration at idle and acceleration
- Clunk on shift changes
- Trans may sag visibly
- Driveshaft angle becomes wrong (premature U-joint wear)
- Exhaust system contacts chassis
Trans mount types
Stock rubber mount (OEM)
Material: Rubber with metal core
Pros: Best NVH (noise/vibration/harshness), quiet, comfortable
Cons: Wears out with age (typically 50-150K miles), softer feel
Lifespan: Original or aftermarket OE-style: 100-150K miles
Best for: Daily drivers, OE replacement
Polyurethane mount
Material: Hardened polyurethane (typically 80A-90A durometer)
Pros: Lasts longer than rubber, better drivetrain feel, doesn't sag
Cons: More NVH (transmits some vibration), slightly noisier
Lifespan: Often outlast vehicle ownership
Best for: Performance applications, towing, daily driver wanting more direct feel
Solid metal mount (race)
Material: Aluminum or steel
Pros: Maximum drivetrain rigidity, race performance
Cons: Significant NVH, transmits all vibration to chassis
Lifespan: Forever (no rubber to wear)
Best for: Race, drag, sled pull, off-road competition
When to upgrade the mount
Stock daily driver with stock mount
Keep stock mount. Replace with OE quality when worn ($30-80 typical).
Tow rig
Upgrade to polyurethane. Stock mount wears quickly under tow load. $40-100 for poly mount.
Performance / modified
Polyurethane minimum. Solid mount if going race. $40-200.
Race / extreme performance
Solid mount or polyurethane. $80-300.
Slight vibration concerns
Stay with rubber. Replace OEM when worn.
Common mount applications
4L60E in stock truck (Silverado, Tahoe)
- Stock rubber: $25-45
- Quality aftermarket OE-style: $30-60
- Polyurethane (Energy Suspension): $50-100
- Solid (race builds only): $80-200
4L80E in 2500HD
- Stock: $30-60
- Aftermarket OE-style: $40-80
- Polyurethane: $60-120
- Solid: $100-200
TH350 / TH400 (older trucks, race builds)
- Wide aftermarket selection
- Stock: $20-40
- Polyurethane: $40-100
- Solid race: $80-300
700R4 (similar to TH350 mounting)
- Stock: $25-50
- Polyurethane: $50-100
47RE / 48RE (Dodge Cummins trucks)
- Stock: $30-60
- Polyurethane: $60-120
- Solid (race builds): $100-250
68RFE (newer Cummins)
- Stock: $40-80
- Polyurethane: $80-150
- Solid: $120-300
Allison 1000
- Stock: $40-80
- Polyurethane: $80-150
- HD options available
How to identify a bad mount
Signs of failed mount:
- Visible cracks in rubber
- Mount sagging (trans hangs low)
- Trans contacts chassis or surrounding components
- Mount has separated from frame
- Visible fluid leak nearby
Driving symptoms:
- Severe vibration at idle in gear: Mount failure causing trans to wobble
- Clunk on shift: Mount allowing excessive movement
- Vibration on acceleration: Mount letting trans rotate too much
- Exhaust hits chassis: Trans sagged, exhaust pulled down
- Bad driveshaft angles: Mount sagged, driveshaft now at wrong angle
Visual inspection:
1. Lift vehicle safely (jack stands or lift)
2. Locate trans mount (typically rear or tail section of trans)
3. Look for visible cracks or separation in rubber
4. Push up/down on trans — should be firm with minimal movement
5. Check that mount is still bolted properly
Replacement procedure
Tools needed:
- Floor jack with wood block (to support trans during replacement)
- Jack stands for safety
- Wrench set (typically 13mm-19mm for various bolts)
- Possibly impact gun for stubborn bolts
Step-by-step:
1. Position vehicle safely on lift or jack stands
2. Locate trans mount (rear of trans, attached to crossmember)
3. Support trans with jack under pan (use wood block to protect)
4. Remove crossmember bolts that mount to frame
5. Remove trans mount bolts connecting mount to crossmember
6. Remove old mount
7. Install new mount in same orientation
8. Reinstall hardware to torque spec
9. Verify trans is properly supported before lowering vehicle
10. Test drive and verify no abnormal vibration
Difficulty: Easy to medium
- 1-2 hours for experienced DIYer
- May require specific socket sizes
- May require working in awkward position
Shop cost:
- Parts: $40-300 depending on mount type
- Labor: 1-2 hours, $100-300
- Total: $140-600
When mount issue is more than just the mount
Multiple components worn:
If trans mount is failing, often other components are worn too:
- Engine mounts (often worn together with trans mount)
- Driveshaft U-joints (worn from bad angles)
- Drive shaft itself (damaged from bad mount)
- Crossmember bolts loose or worn
Address everything at once:
If mount has failed at 100K+ miles, plan to check:
- Engine mounts
- Driveshaft and U-joints
- Crossmember integrity
- Surrounding hardware
Total cost may be $300-800 for complete drivetrain mount refresh.
Specific HD applications
Lifted trucks
Lifted trucks may need specific mount or spacer kit. Verify with manufacturer.
Engine swap
LS swap or similar may need adapter mount. Aftermarket kits available.
High HP applications (500+ HP)
Polyurethane minimum. Solid mount for race.
Diesel applications
Dodge Cummins, Duramax, Powerstroke benefit from poly upgrades due to higher torque.
Brand recommendations
Stock OEM-equivalent
- ACDelco
- Anchor
- DEA Products
- Quality aftermarket from Rock Auto, etc.
Polyurethane
- Energy Suspension - Industry standard, wide application
- Prothane - Quality alternative
- DT Swiss - Heavy-duty applications
- Daystar - Lifted truck applications
Solid race
- Innovative Mounts - Performance applications
- Spohn Performance - Drag race applications
- TCI - Various performance applications
- ATI - Race-grade
Specific application brands
- Mopar for stock Cummins applications
- Motorcraft for Ford applications
- GM for GM applications
Cost comparison
Stock rubber replacement: $30-80 parts
Polyurethane upgrade: $50-150 parts
Solid race mount: $80-300 parts
Full mount refresh (engine + trans): $80-250 parts
With labor:
- DIY: parts cost only
- Shop: $150-600 total
What we sell
OE-quality stock mounts, Energy Suspension polyurethane mounts, Prothane mounts, and HD/race mounts for various transmission applications. Plus crossmember hardware and complete mount kits.
Need a transmission mount? Shop our mounts catalog. Stock, polyurethane, and HD/race mounts for every common application. Free shipping over $70.
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