AW55-50SN Tcc Solenoid, new and ready to install. Fits the AW55-50SN. Ships fast from the USA.
When a Volvo, Saab, Saturn Vue or Chevrolet Malibu with the Aisin Warner five-speed starts flickering the tachometer at a steady 35 mph, bumps on the 1-2 shift, or lets the engine run free on a downhill coast, the part most often behind it is the linear lock-up solenoid, called the SLU. This listing is that single solenoid, sold new: an aftermarket A21425A unit with the black connector, cross-referenced to industry number 59925D, for the AW55-50SN and AW55-51SN from 2000 on. It replaces only the SLU, so you are not paying for an SLT and SLS you may not need. It ships from the USA.
On this transmission the converter clutch is not switched on and off by a simple valve. The TCM pulses the SLU with a varying duty cycle, and the solenoid's output moves the lock-up control valves so the converter clutch can slip a controlled amount at light throttle, then lock fully at cruise. The SLU is normally closed. Sonnax notes that besides converter apply it also controls the B-4 servo apply and B-2 neutral control, and that it is pulsed during the 1-2, 2-1, 2-3 and 3-2 shifts and on engagement into Drive or Reverse. That is why a weak SLU rarely produces a lock-up complaint alone; a firm 1-2 shift usually comes with it.
Read the transmission module with a scan tool that can reach it, and set the fluid level by the factory hot-check method first, because wrong level upsets every linear solenoid. Measure the SLU at its connector; the AW55 linear solenoids should read 5.0 to 5.6 ohms. The most telling check is cooler flow. Sonnax describes a correct SLU as producing a sharp, brief drop in cooler flow of roughly half when the transmission is put into Drive, then a return to normal. If shifts are harsh and that toggle never appears, the SLU is not responding. Clean the Hall-effect input and output speed sensors and keep their wiring away from the solenoid harness too; interference there can produce converter cycling and phantom codes with a good solenoid. Our converter clutch shudder diagnosis guide covers telling a solenoid problem from a worn converter, and the AW55-50SN service guide covers the valve body wear that mimics it.
The AW55 linear solenoids changed during production: the early SLT and SLS use a narrow bracket and short manifold, the late ones a wider bracket and long manifold. Sonnax confirms the SLU stayed the same through both, and this listing is described as fitting all early and late valve bodies, 2000 and up. It may fit AW55-50SN and AW55-51SN applications from Volvo, Saab, Saturn, Chevrolet, Pontiac, Opel, Nissan and Ford. Before ordering, compare your old solenoid with the photos, confirm the black connector, and check the number on your part against A21425A or 59925D. If you are unsure, send us the year, model and VIN. Everything else for this family is on our Aisin parts page.
If more than one linear solenoid tests out of range, the matched SLT, SLS and SLU set is the better buy. A scored lock-up or modulator bore calls for a replacement AW55-50SN valve body.
| Fits | AW55-50SN |
| Part type | Tcc Solenoid |
| Condition | New |
| Brand | OEM |
| Reference | A21425A |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
One solenoid: the SLU linear lock-up solenoid with the black connector, part A21425A. The SLT and SLS linear solenoids and the on/off shift solenoids are sold separately.
The bracket and manifold length changed on the SLT and SLS during production, but the SLU stayed the same, and this listing is described as fitting all early and late AW55-50SN and AW55-51SN valve bodies from 2000 on. Match the black connector and your old part number before installing.
That RPM fluctuation during modulated converter clutch apply is one of the classic SLU symptoms on this transmission. Check fluid level, resistance (5.0 to 5.6 ohms) and the cooler flow drop on engagement before replacing it.
Often it works as delivered. If the road test still shows cycling at 30 to 40 mph or a harsh lock-up, the SLU adjuster can be turned in small steps. Turning it in firms the shifts and delays lock-up; turning it out softens shifts and brings lock-up earlier. One to two turns is normally all that is needed.
Use the JWS 3309 type Aisin fluid your vehicle maker calls for and set the level with the engine running at operating temperature. Then clear codes and drive several cycles so the TCM relearns.
