GM 4L80-E Archives - Transmission Digest
From one problem to the next: When a simple solution becomes complicated

A 2007 Chevrolet Express 3500 comes to our shop with a concern of no reverse and very little forward movement. A quick check of codes reveals the following: P0171 Fuel Trim System Lean B1 Po174 Fuel Trim System Lean B2 P0218 Transmission Fluid Overtemp P0300 Engine Misfire Detected P0455 Evap Leak P0753 1-2 Shift Solenoid

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Sonnax highlights adjustable rear servo pin kit

Sonnax highlights its adjustable rear servo pin kit (part number 34912-01K), which allows users to replace servo pins in GM TH400 and 1995 and earlier 4L80-E transmissions. OE pins have seven different lengths to allow for adjustment of the Low/Reverse band but are no longer available from GM. This pin kit has an adjustment range

Sonnax introduces Low/Reverse servo pistons for GM TH400, 4L80-E

Sonnax has introduced new Low/Reverse servo pistons for GM applications. According to the company, the new pistons are built for GM TH400 and 4L80-E transmissions, and are made of high-strength, billet aluminum to prevent failure.

GM 4L80/85-E Extreme Duty Input Shaft

Input shaft failure is common in performance GM 4L80-E and 4L85-E units running with extreme horsepower. OE and aftermarket shafts simply don’t hold up in these conditions, leading to spline twist and shaft breakage. Recommended for applications above 1,000-hp, the Sonnax extreme duty input shaft (p/n 34670-02) is manufactured from high-strength Aermet steel alloy with

GM 4L80/85-E 2-3 Accumulator Spring

This new Sonnax 2-3 accumulator spring (p/n 34931-01) for GM 4L80/85-E units is a direct replacement spring that has been stress relieved and shot-peened for increased durability compared to factory springs.

Vacuum testing the GM 4L80-E

From the TASC Force we reprint a series of in-depth test instructions for checking the serviceability of valve bodies.

Which Planet Are You On?

As most rebuilders know, in 1997 the 4L80-E went to a center-gearbox lubrication system by relocating the cooler return line from the pump to the center support. As a result, many internal hard parts were redesigned to accommodate this new lubrication system, as illustrated in figures 1 through 5 taken from an ATSG bulletin.

Repeat Performance, Not by Popular Demand

You may recall that the 4L80-E made its appearance in 1991. And whether it was in two-wheel-drive or four-wheel-drive configuration, the output carrier had the exciter ring for the output-shaft-speed (OSS) sensor pressed onto it.