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Sonnax Transmission Company

Sonnax Clutch Backing Plates

5.0 out of 5 stars 8 Customer Reviews

GM 6L80 and 6L90 transmissions often suffer failure of the 4-5-6 clutch assembly due to flexing and bowing of the backing plate (coning)—especially when your clutch-apply pressures exceed OE specifications. Sonnax clutch backing plates are designed to minimize flexing/bowing when the clutch is applied, drastically reducing the likelihood of clutch plate distortion. Their stiffer backing plate design outperforms OE and aftermarket plates.

Showing In Stock Items. Show All 7 Items.

Results 1 - 5 of 5

Sonnax Clutch Backing Plates 74140-01K

Sonnax Clutch Backing Plates 74140-01K

Sonnax Clutch Backing Plates 74140-01K

Clutch Backing Plate, 4L60, 700R4, 4L60E, 4L65E, 4L70E, Kit

Part Number: SOX-74140-01K

5.0 out of 5 stars ( 8 )

Estimated Ship Date: Monday 4/20/2026 if shipped by air

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Estimated Ship Date: Monday 4/20/2026 if shipped by air

Sonnax Clutch Backing Plates 34144HD-02

Sonnax Clutch Backing Plates 34144HD-02

Sonnax Clutch Backing Plates 34144HD-02

Clutch Backing Plate, 4L80-E, 4L85-E, Kit

Part Number: SOX-34144HD-02

Not Yet Reviewed

Estimated Ship Date: Monday 4/20/2026 if shipped by air

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Estimated Ship Date: Monday 4/20/2026 if shipped by air

Sonnax Clutch Backing Plates 34144HD-01

Sonnax Clutch Backing Plates 34144HD-01

Sonnax Clutch Backing Plates 34144HD-01

Clutch Backing Plate, THM400, 4L80-E, Kit

Part Number: SOX-34144HD-01

Not Yet Reviewed

Estimated Ship Date: Monday 4/20/2026 if shipped by air

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Estimated Ship Date: Monday 4/20/2026 if shipped by air

Sonnax Clutch Backing Plates 35570-75

Sonnax Clutch Backing Plates 35570-75

Sonnax Clutch Backing Plates 35570-75

D Clutch Backing Plate HD

Part Number: SOX-35570-75

Not Yet Reviewed

Estimated Ship Date: Monday 4/20/2026 if shipped by air

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Estimated Ship Date: Monday 4/20/2026 if shipped by air

Sonnax Clutch Backing Plates 36965-03

Sonnax Clutch Backing Plates 36965-03

Sonnax Clutch Backing Plates 36965-03

BACKING PLATE

Part Number: SOX-36965-03

Not Yet Reviewed

Estimated Ship Date: May 18, 2026 if ordered today

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Estimated Ship Date: May 18, 2026 if ordered today

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