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  • Wear grooves in the Forward drum ID bore
  • Burnt Forward clutch
  • Delayed engagement


The input shaft contacts the forward drum bore ID due to tight clearances and accumulated bushing wear.


Install the Sonnax oversized seal rings after boring the forward drum to the recommended diameter.

4L80-E, 4L85-E

Oversized Seal Rings
Part No. 34716-01

Package Quantity: 2

View Instructions

The 4L80-E forward drum is often replaced due to wear of the sealing ring bore caused by contact with the input shaft. Contact between shaft and drum occurs because of looseness/wear of the support bushings and tight clearance between shaft and drum bore. Worn drums can be salvaged by machining away the worn area, increasing the bore ID to .900 and installing the Sonnax oversized outer diameter forward drum sealing rings 34716-01. The oversized seal diameter restores proper sealing with the larger bore, while the increased clearance reduces future wear by making clearance consistent with other applications. This fix works on all 4L80-E forward drums.

  • Salvages all 4L80-E forward drums with grooves worn in the ID bore.
  • Reduces the likelihood of future contact between forward drum ID and input shaft.
  • Material: PTFE
  • Seal Style: Solid
  • Height: 0.096"
  • Width: 0.101"
  • Outer Dia.: 0.918"
  • 34716 01 combo
  • 34716 01