Safeguard performance GM TH400 and 4L80-E vehicles on the street and track with reliable, high-strength servo upgrades from Sonnax – the leader in transmission innovation.

New for fall 2021, Sonnax billet aluminum Low/Reverse servo pistons prevent failure at any power level — a critical safeguard when cast OE pistons are brittle and prone to breaking. Part No. 34914-01 fits all TH400 and ’95-earlier 4L80-E; Part No. 34914-02 fits ’96-later 4L80-E.

Also new for TH400 and ’95-earlier 4L80-E applications is an adjustable servo pin kit (Part No. 34912-01K) that gives builders easy access to five of the seven pin options discontinued by GM. The pin covers the five longest lengths for accurately setting Low/Reverse piston travel. It features an O-ring groove to prevent leakage of line pressure past the case pin bore.

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