It is often difficult to reduce front unit endplay on GM TH400 or 4L80-E and 4L85-E units with excessive spline wear. Normal component wear allows excess forward and direct drum travel. This travel or free-play reduces sealing ring life. These units are limited on the thickness of pump shim material that can be added. Excessive shimming at the pump will push the forward drum off the rings and result in a burnt forward clutch. Sonnax offers .010" thick front/rear unit endplay shim 34500-Z that can be stacked under the sun gear bearing race.

• By lifting the sun gear, the drums are also supported and front unit endplay is reduced
• The shim can be installed between the sun gear thrust bearing and the rear internal gear during lower unit assembly
• Updated design fits all model years