4L80E, 4L85E

Symptoms:

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

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

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

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 these Sonnax oversized outer diameter forward drum sealing rings. 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

Note: Tool kit 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.

Specifications:

• Material: PTFE
• Seal Style: Solid
• Height: 0.096"
• Width: 0.101"
• Outer Dia.: 0.918"

38254K Instruction Sheet