Nine-piece solenoid set for 1997-2003 GM 4L80E and 4L85E MT1 and MN8 units: shift A and B, TCC/PWM, EPC, internal harness, filter, gasket and speed sensors.
A 1997-2003 Chevy or GMC 2500 or 3500 with a 4L80E that drops into second gear, slams every shift, loses the speedometer, or sets P0720, P0722, P0753 or P0758 has an electrical problem until proven otherwise. This nine-piece set replaces the whole electrical package on the MT1 4L80E and MN8 4L85E in one pan drop: all four solenoids, the internal harness, both speed sensors, the filter and the pan gasket. The speed sensors are the difference between this kit and a plain solenoid set, and they are the reason to pick it when your truck has codes from both camps.
The 4L80E makes four forward gears (2.482, 1.482, 1.000 and 0.750) with only two on/off shift solenoids. The A solenoid (24230288) is on in 1st and 4th, the B solenoid (24230289) is on in 3rd and 4th, and with both off the hydraulics default to 2nd. The EPC solenoid (24220158 in this set) is a variable-current force motor that sets line pressure, and the TCC/PWM solenoid (24210864) applies the converter clutch. None of that works without good speed data: the controller divides input speed by output speed to know what gear it is actually in, and uses output speed as road speed for the shift schedule, lockup and the speedometer. That is why the 24203876 input and output sensors belong in the same job as the solenoids.
Pull codes first and watch input and output speed on a scan tool while driving. An output signal that drops to zero while the truck is rolling, or an input reading that does not match engine speed with the converter locked, points at a sensor or its two-wire circuit. For the solenoids, measure through the case connector: the published range for these on/off shift solenoids is about 19 to 31 ohms. Our 4L80E speed sensor symptoms guide walks through the sensor checks, and the shift solenoid diagnosis guide covers the A and B gear-pair logic. If line pressure is the complaint, rule out worn valve body bores too, because a new EPC solenoid cannot fix a leaking regulator circuit.
This set is built for the 1997-2003 GM 4L80E and 4L85E, RPO MT1 and MN8, using the 24222798 internal harness. That covers the heavy-duty Chevrolet and GMC 2500 and 3500 pickups, Suburban 2500, Express and Savana vans and other GM applications from those years. The 2004-up units changed the harness and the EPC part number, so a 2004 or newer truck needs a later kit. Match the part numbers on your old solenoids and harness to the ones listed here, or send us your year and VIN and we will confirm it. You can see every part we stock for this unit on the 4L80E parts page.
It is a pan-off job with the transmission in the truck. Drain and drop the pan, pull the filter and the seal from the case bore, and unplug the harness from each solenoid and from the case pass-through connector. The A and B solenoids each come off with one bolt and bracket; the EPC and TCC/PWM solenoids slide out of their bores. Fit new O-rings (lubricate them with ATF), route the new harness exactly where the old one ran, and check that the pass-through connector is seated with all of its retention tabs intact. The speed sensors mount on the outside of the case, so replace them with fresh seals and clean the mounting faces. Set the new filter square in its bore, install the pan on the new gasket, torque the bolts evenly, refill with Dexron VI and set the level hot. Clear codes and drive it through all four gears plus a lockup cycle. If the clutches are already slipping, a 1997-2009 clutch module or a full 4L80E master rebuild kit is the right companion rather than electrical parts alone.
| Fitment | GM 4L80E and 4L85E, RPO MT1 / MN8, 1997-2003 |
| Pieces | 9 (4 solenoids, internal harness, filter, pan gasket, input and output speed sensors) |
| Solenoid part numbers | TCC/PWM 24210864, EPC 24220158, A shift 24230288, B shift 24230289 |
| Harness | 24222798 |
| Filter and gasket | Filter with seal 24210956, pan gasket 8677743 |
| Speed sensors | Input and output, 24203876 |
| Condition | New, not remanufactured |
| Shipping weight | 1 lb |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. This set is for 1997-2003 MT1/MN8 units with the 24222798 internal harness. 2004 and later units use a different harness and EPC solenoid, so pick one of our 2004-up kits instead, or send your VIN and we will match it.
Because a 4L80E that loses output speed goes to second gear with maximum line pressure, which feels exactly like a solenoid failure. If you have speed sensor codes, a dead speedometer, or sensors that are the same age as the solenoids, doing both at once means one pan drop and one road test instead of two.
No. The solenoids, harness and filter are all reached by dropping the pan, and the input and output speed sensors bolt to the outside of the case. Plan on a few hours plus a fluid refill.
Dexron VI. It is back-serviceable for the older Dexron III applications these trucks originally called for. Check the level hot, in Park, after a drive.
Check the circuit outside the transmission: the case connector, the wiring to the controller, and the controller grounds. Shift solenoid circuit codes mean the module did not see the voltage change it expected, and a chafed wire or corroded pin will set them just as fast as a bad coil.
Clear the codes and drive the truck through every gear and a lockup cycle. Controllers that keep adaptive pressure tables should have them reset with a scan tool so shift feel settles quickly on the new parts.
