Shift and TCC solenoid rebuild kit with internal harness, filter and pan gasket for GM 4L80E and 4L85E in 1991-2009 heavy-duty trucks and vans.
Work trucks and cargo vans with a 4L80E rack up miles and heat, and sooner or later the electrical parts under the pan give out. If your Silverado or Sierra 2500HD, Suburban 2500, Express or Savana van, or Hummer H1 is stuck in one gear, flaring between shifts, never locking the converter, or setting P0753, P0758 or P0740, this kit covers the whole electrical side in a single pan drop. The photos show the internal wiring harness with its round case connector, four solenoids (EPC pressure control, shift A, shift B and the TCC lockup solenoid), a filter and a full pan gasket.
The 4L80E has no throttle cable or governor. The computer picks every gear by switching shift solenoids A and B on and off in different combinations, and each combination strokes the shift valves to a different gear. The EPC solenoid works differently: it receives a varying current and turns that into line pressure, which decides how firmly the clutches apply. The TCC solenoid applies the converter clutch at cruise. Every one of those parts gets power and ground through the internal harness, which runs around the valve body to a pass-through connector in the case. A cracked wire anywhere on that loop looks to the computer exactly like a dead solenoid.
A circuit code means the computer saw the wrong voltage or current, and the fault can be the solenoid, the harness or something outside the transmission. Measure each solenoid through the case connector, then again at the solenoid once the pan is down; our shift solenoid A and B guide walks through it. Do not skip the supply side. Transmission Digest documented a 2007 Express 3500 that kept setting P0758 after the transmission, harness and solenoids had all been replaced; voltage to the shift solenoids sagged as the truck warmed up, and the real fault was a failing ignition switch feeding that fuse circuit. Van owners should also read the Express van problems guide before ordering.
The listing names 1991-1999 C/K 2500 and 3500, 1999-2007 Silverado and Sierra 2500HD and 3500, 1991-2007 Suburban 2500, 1996-2007 Yukon XL 2500, 1996-2009 Express and Savana 2500 and 3500, 2002-2006 Avalanche 2500 8.1L and 1992-2006 Hummer H1, with the 5.0L, 5.7L, 6.0L, 7.4L, 8.1L and 6.5L diesel engines. Be aware that GM changed the 4L80E electrically during that span. Sonnax lists separate early and late valve bodies, offers an adapter for running an early ('92-'02) EPC solenoid in a late ('03-later) unit, and calls the late case connector the gray style. The harness in the photos has the gray round connector, and its cross references include harness 24200161. Before ordering for an early truck, compare your case connector, EPC plug and harness routing with the photos, or send us the year and VIN and we will confirm. Everything we stock for this unit is on the 4L80E collection page.
Drain the fluid and lower the pan, then twist the filter out and check that its seal did not stay in the case bore. Unplug the harness from each solenoid and from the pass-through, release its clips, and remove the solenoid bolts and retainers. Lay the old and new parts side by side to match plugs before anything goes back in. Wet each O-ring with ATF, seat the solenoids fully, and follow the original harness path so nothing rubs the valve body or filter. Inspect the plastic retention tabs on the case connector; Sonnax notes one of the three commonly breaks, letting the connector push into the pan. Install the filter and gasket, tighten the pan bolts evenly, fill with Dexron VI and check the level hot. Clear codes and drive through all four gears and lockup.
If the pan comes off a high-mileage unit with clutch material in it, the electrical refresh will not save it; plan on the 4L80E master rebuild kit instead. For tow rigs that also need firmer shifts, the 4L80E shift kit goes in during the same service.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Both fall inside the listed 1991-2009 range. The harness pictured uses the later gray case connector, so match your case connector and EPC plug to the photos, or send us the year and VIN and we will check before it ships.
The photos show four: the EPC pressure control solenoid, shift solenoids A and B, and the TCC lockup solenoid, along with the internal harness, filter and pan gasket.
Possibly not. If the code returns with new parts, check the supply voltage to the solenoids with the engine warm. A documented 2007 Express case traced a repeat P0758 to a failing ignition switch, not the transmission.
Dexron VI. It is GM's current specification and is approved as a back-service fluid for the Dexron III and IIE trucks of earlier years. Check the level hot with the engine idling.
Clear the codes, then drive the truck through every gear and a converter lockup at cruise. Shift feel can take a few drive cycles to settle as the computer adapts.
