Stock-depth 2-1/4 in finned oil pan for the GM Turbo 400 with a drain plug, gasket and bolts, so fluid services stop meaning a pan drop.
If every fluid change on your Turbo 400 ends with ATF running down your arm, or the pan has been bent by a jack, a curb or road debris and now weeps at the rail no matter how many gaskets you try, this is the part. It is a finned black replacement oil pan for the GM Turbo Hydra-Matic 400 (TH400, later called the 3L80) with a drain plug already installed, plus a pan gasket and a set of bolts and washers. It crosses to reference number SP8593BK and keeps the factory depth, so it fits the stock filter and pickup and hangs no lower than the pan you are taking off.
The TH400 is a sump design: the pan holds the fluid supply, and the filter and intake pipe sit down in it, feeding the front pump through an O-ring seal in the case. The factory pan has no drain. To service the unit you loosen the bolts and let fluid pour over the rail, which is messy, makes it hard to look at what came out, and tempts people to skip services. With a plug you drain it hot into a clean container, read the fluid and debris, then drop a nearly empty pan to change the strainer. Because the pan rail is also the sealing surface for the whole bottom of the case, a distorted rail is one of the most common TH400 leak points.
GM's own TH400 service manual lists three causes of a pan leak: bolts not torqued correctly, a damaged or badly installed gasket, and a gasket face that is not flat. If the first two are already ruled out, the pan is the problem.
Clean the case and pan with brake cleaner, drive until the fluid is hot, and look again. Fluid that shows first at the pan rail is a pan or gasket leak; fluid that starts higher, at the modulator, cooler line fittings or the shift shaft, will only run down to the pan and fool you. Our TH400 filter and pan service guide walks through the drop, cleanup and what to read in the debris. If the fluid shows heavy clutch material or metal, step through the TH400 common problems guide before spending money on a pan.
This pan fits the GM TH400 / Turbo 400 / 3L80 three-speed automatic used in GM trucks, motorhomes, muscle cars and full-size cars from the mid-1960s through about 1990, plus the many swap and street-rod builds that use one. The TH400 pan pattern did not change over that run, but it is easy to confuse with a TH350 or 4L80E pan, so check your unit with our TH350 vs TH400 identification guide. The listing gives the depth as a stock 2-1/4 in; other references for this pattern quote about 2-3/8 in, so treat it as stock depth and check clearance at the crossmember and exhaust on lowered cars. If you want more fluid capacity instead, look at the TCI 228000 deep pan. Not sure what you have? Send the year, the vehicle and the VIN. More parts for this unit are on our TH400 parts page.
If the pan is coming off because the unit is slipping or shifting soft, plan on the parts that fix the cause, such as the TH400 shift improver kit or a full overhaul kit.
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| Drain plug | |
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| Hardware | |
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| Finish |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is the TH400 / 3L80 pan pattern. TH350 and 4L80E pans have different shapes and bolt patterns. Count the pan bolts and compare the outline, or send us your year, vehicle and VIN to check.
No. It keeps the factory depth, so the stock TH400 strainer and intake pipe sit at the correct height. A deep-pan filter is only needed with a deeper pan.
Use Dexron-type ATF; current Dexron VI is back-serviceable for older Dexron specs. Add a few quarts, start the engine, run through each range, then top up to the hot mark in Park on level ground. Do not fill to a fixed number because the amount drained varies.
GM lists the TH400 pan-to-case bolts at 12 lb-ft and the filter retainer bolt at 10 lb-ft. Use a torque wrench and a cross pattern; the aluminum case threads strip easily.
Yes. The pan is already off, the strainer is a wear item, and the intake pipe O-ring hardens with age and can pull air into the pump. Change both at the same time.
Use the gasket dry. RTV squeeze-out inside the pan can break off and end up in the strainer or valve body, and it is not needed on a flat rail.
