5R55S Sun Shell, new other (see details) and ready to install. Fits the 5R55S. Ships fast from the USA.
Owners of a 2004-and-later Explorer or Mountaineer, a 2005-2010 Mustang V6, or a 2003-and-later Lincoln LS or Thunderbird usually land on this page after a rebuilder calls with bad news: the sun shell in the 5R55S is cracked, its splines are chewed up, or the bearing surface inside it is scored. This listing is a new original Ford sun shell for the 5R55S. It is the shell only, listed with a 55-tooth engagement and a bearing-style design, meaning it uses a bearing inside rather than a bushing. It is also listed for the 5R55W and 5R55N.
The 5R55S is a five-speed that uses clutches and three bands rather than the intermediate clutch and sprag of the earlier 5R55N. The sun shell is the stamped steel link between the direct clutch drum and the sun gear of the main gear set. When the direct clutch is on, its torque reaches the gear train through this shell; Transmission Digest describes the direct clutch as the element that applies when you select Reverse, so a weak link here shows up quickly in reverse. When the intermediate band clamps the direct drum, the shell is what keeps the sun gear from turning. Because the shell passes torque in both directions, a hairline crack near the hub or rounded teeth can turn into a sudden loss of a gear.
Most 5R55S complaints are hydraulic, not hard-part failure. Sonnax points to worn valve body bores, especially the main regulator, TCC modulator and VFS modulator bores, as the reason this unit slips or sets ratio codes, and servo pin bore wear is another known cause. Scan for codes, check the fluid, and work through our 5R55 diagnostic walkthrough and the 5R55S no-reverse guide. A shell is the answer when the unit is apart and you can see the damage.
This shell is listed for the 5R55S, 5R55W and 5R55N. Sonnax notes the S replaced the N in Lincoln LS and Thunderbird for 2003 and replaced the W in Explorer and Mountaineer for 2004-2005. Be careful with the N: Sonnax also warns that only a few N parts carry over to the W and S. The S and W differ in their overdrive sun gear, 38 teeth on the S versus 24 on the W, but that gear is in the overdrive planetary, not this shell. Match the tooth count and bearing style to your old shell, or send us your year and VIN. The full lineup is on the 5R55 transmission page.
Pair the shell with a 5R55S rebuild kit, and check the 5R55S reaction shell for cracks while the unit is open.
| Fits | 5R55S |
| Part type | Sun Shell |
| Condition | New Other (See Details) |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is listed for the 5R55S with a 55-tooth, bearing-style design. Match the tooth count and bearing style to the shell you removed, or send us the year and VIN and we will confirm before it ships.
No. This listing is the shell only. Reuse your sun gear if its splines and bushing surfaces are good, or replace it if they are worn.
This shell is listed for both. The best-known W and S difference is the overdrive sun gear, 24 teeth on the W and 38 on the S, which is a different part in a different gear set.
Yes, because the direct clutch applies in reverse and drives through this shell. A stuck low/reverse servo valve or worn valve body can also cause delayed reverse, so diagnose before you tear down.
Mercon V. Check the level at the fluid level plug with the engine running and fluid at 81-120 degrees F, then run an adaptive relearn.
