Updated solenoid block for Ford 5R55W and 5R55S transmissions, replaces 9L2Z-7G391-AA. Fixes harsh or erratic shifts and solenoid fault codes.
Searching for 9L2Z-7G391-AA usually means one thing: a Ford Explorer, Mountaineer, Mustang V6 or Lincoln LS with the 5R55W or 5R55S five-speed is flaring between gears, banging into third, or setting pressure control codes, and you have read that the solenoid block is the weak point. This is the updated-design block for those transmissions. It replaces Ford 9L2Z-7G391-AA as well as the 9L2Z-7G234-AA and 4L2Z-7G234-AA numbers and the common 58879WD and D46420B interchange numbers. It is the block only, with no filter, so plan to buy a filter and pan gasket with it.
The block carries every solenoid in the transmission: four on/off shift solenoids, a pulse width modulated TCC solenoid, and three variable force pressure control solenoids called PCA, PCB and PCC. PCA and PCB are commanded in opposite directions to raise and lower mainline pressure and to stroke the boost valves, and PCC handles reverse engagement and the direct clutch in fourth and fifth. Because shift feel depends on those three pressure solenoids, small changes in how a block responds show up right away as flare or harshness. According to an ATRA technical bulletin, Ford's later-design pack for 2004-on transmissions was originally 4L2Z-7G391-AA, and Ford now recommends only the updated 9L2Z-7G391-A design on those units. That is the part this listing replaces.
A new block cannot save a unit with burned fluid or worn clutches, so look in the pan before you buy. Check the case connector and harness for oil wicking and broken pins, and read live data for solenoid commands. Also rule out servo pin bore wear, which causes slipping and P0735 on these cases and is often misdiagnosed as a solenoid problem. The 5R55S limp mode guide and our 5R55 harsh or delayed shifts walkthrough lay out the checks in order.
The listing names the 5R55W and 5R55S in 2002-up Explorer, Sport Trac and Mountaineer with the 4.0L and 4.6L, the Aviator 4.6L, the 2005-2010 Mustang 4.0L and 4.6L, and the 2003-2006 Lincoln LS 3.0L and 3.9L. Be careful with the early years. The ATRA bulletin says 2002-2003 Ford units with the W or S, and the 2003 Lincoln, use the early pack, 1L2Z-7G391-AG, and that putting the wrong pack in is a known cause of a 2-3 flare after a rebuild. For a 2004 or newer truck, Mustang or LS, this updated block is the one Ford recommends. If you own a 2002-2003, check the number on your old block and send it with your VIN before ordering. It does not fit the 5R55E in the Ranger and early Explorer, which uses separate solenoids. Browse the full 5R55 parts page for the rest of this family.
| Fits | Ford 5R55W, 5R55S automatic transmissions |
| Replaces | 9L2Z-7G391-AA, 9L2Z-7G234-AA, 4L2Z-7G234-AA, 58879WD, D46420B |
| Design | Updated solenoid block |
| Weight | 2.84 lb |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
For 2004 and newer Ford 5R55W and 5R55S units, Ford recommends the updated 9L2Z design, which is what this block replaces. Read the number on your old block to be sure, or send us your VIN.
Be careful. Those years used the early pack, 1L2Z-7G391-AG, and the early and late packs deliver slightly different pressures. A mismatched pack can cause a 2-3 flare. Send us your old block number and VIN before ordering.
No, this is the solenoid block only. Buy a filter and pan gasket with it, or choose our 5R55W/5R55S block kit that includes them.
Ford's service procedure lists eight bolts at 71 lb-in (8 Nm), tightened in sequence. That is inch-pounds, not foot-pounds, so use an inch-pound wrench.
Only if pressure control is the cause. Burned clutches or servo pin bore wear cause slipping that no solenoid block can fix, so check the fluid and pan debris first.
Mercon V. Check the level hot at the T30 Torx fill and level plug.
