TH400 Planetary 1964-98, used and ready to install. Fits the TH400. Ships fast from the USA.
When a Turbo 400 howls in every gear, drops metal into the pan, or will not hold in Park because the pawl has been ratcheting on worn lugs, the rear planet carrier is a common casualty. This is a used, original GM rear planetary for the TH400, the lighter TH375 and the early 4L80E, listed for 1964 through 1998 Chevrolet, Buick, Oldsmobile, Pontiac and GMC applications. It is a budget way to replace a carrier with damaged pinions or a cracked body without buying a complete gear unit. The listing notes slight wear on the park engagement area, so read the fitment and install notes before you order.
GM's service manual calls this part the output carrier. It sits at the back of the compound gearset, splined to the output shaft and held to it with a snap ring, and its pinions mesh with the rear internal gear on the mainshaft and with the long sun gear it shares with the front reaction carrier. Because it is tied directly to the output shaft, it carries every bit of torque that reaches the driveshaft in all three gears and Reverse. Its outer edge also carries the lugs that the parking pawl drops into, so this is the part that physically locks the output shaft to the case when you select Park.
GM's noise chart for the Turbo 400 lists the planetary gearset and asks you to clean the thrust bearings and races and inspect them for pitting or roughness, so a gear-train noise always means a teardown, not a guess. Before that, check fluid level and pressures, and look at what is on the pan magnet. Once apart, GM's checks for the output carrier are simple: inspect the pinions for damage, rough bearings or excessive tilt, measure pinion end play (GM lists .009 to .024 inch), inspect the parking pawl lugs for cracks or damage, check the output locating splines, and look the front internal gear ring over for flaking or cracks. Our TH400 common problems and fixes guide and the filter and pan service guide show what normal and abnormal debris look like.
The listing covers 1964-1998 TH400 and TH375 transmissions plus early 4L80E units. GM built many TH400 variants across those years, so compare the spline count, pinion count and overall size with your old carrier, or send us your year, vehicle and transmission ID tag and we will check it before it ships. Because this used part has slight wear on the park engagement area, inspect the lugs on arrival and compare them with your own carrier, especially if your old one failed at the parking lugs. The rest of the TH400 range is in our TH400 parts collection, including the early 1964-1965 front reaction planetary and a complete 1973 planetary gear unit.
| Fits | TH400 1964-98 |
| Part type | Planetary |
| Condition | Used |
| Brand | GM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The rear one, which GM calls the output carrier. It splines to the output shaft and carries the parking pawl lugs. The front planetary is the reaction carrier, which the rear band and low roller clutch hold.
The listing says it fits TH400, TH375 and early 4L80E units. Compare it with your old carrier or send us the year and transmission ID tag before ordering, especially for a 4L80E.
The lugs that the parking pawl locks into show some wear. The carrier still does its job in the gear train, but inspect the lugs and your pawl on arrival, and use the parking brake on steep grades.
Thrust washers, bearings and races in the gear train, the output shaft O-ring, and the clutches and seals if the unit is being overhauled. Check the parking pawl at the same time.
A Dexron-family automatic transmission fluid. Check the level hot in Park after the road test.
