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


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.


Recommended tool kit 34716-TL is no longer in production. Check with your distributor for availability.

4L80-E, 4L85-E

Oversized Seal Rings
Part No. 34716-01

Package Quantity: 2

View Instructions Find a Distributor

GM 4L80-E and 4L85-E forward drums are 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 I.D. 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.

  • Salvages all 4L80-E and 4L85-E forward drums with grooves worn in the I.D. bore
  • Reduces the likelihood of future contact between forward drum I.D. and input shaft

Tool kit [34716-TL] is not required but is highly recommended to prevent damage to the new oversized sealing rings when inserting the input shaft into the machined forwared drum I.D. bore.

  • Material: PTFE
  • Seal Style: Solid
  • Height: 0.096"
  • Width: 0.101"
  • Outer Dia.: 0.918"
  • 4L80-E, 4L85-E Oversized Seal Rings 34716-01
  • 4L80-E, 4L85-E Oversized Seal Rings 34716-01