4L85E Tcc Solenoid 1991, new and ready to install. Fits the 4L85E. Ships fast from the USA.
If your GM heavy-duty four-speed will not lock the torque converter at highway speed, cruises a few hundred RPM higher than it used to, or has set P0741 or P0742, the converter clutch solenoid is one of the first parts to test. This new TCC solenoid carries reference D34418 and is listed for 1991, the first year of the electronic big-case four-speed. That first unit was the 4L80E; the heavier 4L85E followed in 2002 on the same valve body architecture, which is why the part is listed under both names.
At cruise the computer applies the torque converter clutch so the engine and transmission input turn together instead of slipping through fluid. The TCC solenoid is the valve that makes that happen: when energized it redirects oil to the converter clutch apply circuit, and when released the converter goes back to fluid drive. A solenoid that sticks, leaks past its seat, or loses its O-ring seal cannot hold apply oil, so lockup never happens, happens late, or drops in and out. On trucks in this family, many of them towing or hauling at a heavy load, a converter that never locks keeps fluid temperatures high, and heat is what shortens clutch life throughout the unit.
Separate the electrical side from the hydraulic side. A circuit fault is chased with a meter at the case connector, checking feed voltage, resistance and the ground the computer switches. A performance code, as GEARS explains, means the electrical side looked fine but the result did not match the command, and that has three possible causes: the solenoid, a stuck valve in the valve body, or a worn friction element. On a converter clutch that last one includes the converter itself. Watch commanded TCC against engine and turbine speed on a scan tool; if the command is on and slip stays high, the solenoid or the converter circuit is not holding. Our 4L85E solenoid symptoms guide covers the circuit tests, and the 4L85E common problems guide lists the other faults that look similar.
This listing is marked 1991 and carries reference D34418. GM revised the converter clutch controls on this family more than once, and solenoids from different years can differ in connector, O-ring layout and function, so the year alone is not a guarantee. Compare the connector and seal arrangement of your old solenoid to the product photo, and check the number stamped on it. If you are not sure, send your year, engine and VIN and we will confirm before shipping. Every part we stock for this transmission is on the 4L85E collection page.
| Fits | 4L85E 1991 |
| Part type | Tcc Solenoid |
| Condition | New |
| Brand | OEM |
| Reference | D34418 |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The 4L85E was introduced in 2002, but it shares the valve body and solenoid layout of the 4L80E that started in 1991. This listing is marked 1991, so match the connector and stamped number on your old solenoid, or send your VIN, before ordering for a later truck.
The engine stays at higher RPM at highway speed because the converter never locks, fuel economy drops, and you may feel a shudder at 40-60 mph or a stall at stops if it sticks applied.
Yes. A P0741 performance code means lockup did not produce the expected result, and a worn converter clutch causes that as easily as a bad solenoid. Test the circuit and watch slip on a scan tool first.
GM specifies Dexron VI for the 4L80E and 4L85E family. Burnt or dark fluid on a TCC complaint is a sign the converter or clutches have been slipping and should be inspected.
No programming is needed. Clear the codes and drive at steady highway speed through several lockup cycles to confirm the RPM drops when the clutch applies.
