How Do I Replace a TH400 Torque Converter?
The Turbo 400 (TH400) is probably the most popular automatic in the world with hot-rodders and off-roaders. A well-built TH400 can handle more foot-pounds of torque than most engines will ever produce, and can deliver quicker and more consistent 1/4-mile times than any production manual transmission. Higher-stall torque converters allow the engine to get into its power-band quicker and are among the first modifications that the average hot-rodder pursues when using a TH400.
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Things You'll Need
- Full socket set with extensions and universal joints
- Floor jack and jack stands
- Screwdrivers and Allen head wrenches
- Open- and box-end wrenches
- Lint-free rags
- Duct tape
- Transmission fluid
Instructions
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1
Raise the rear end of your car with a jack and set it onto a set of jack-stands. Unbolt the driveshaft from the rear differential and pull it out of the transmission. Stuff a lint-free rag into the transmission output so that it surrounds the output shaft. Cover the rag and the transmission output completely with a layer of duct tape. This will help to keep the fluid inside the transmission instead of spilling all over the floor.
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2
Remove the dust cover from the bottom of the transmission's bell housing to expose the torque converter and engine flexplate. Remove the first converter-to-flexplate bolt that you see. Turn the engine's crankshaft with a large socket connected to the harmonic balancer pulley bolt on the front of the crankshaft. Rotate the crankshaft to expose the next two converter bolts and remove them.
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3
Remove the E-clip that secures the shift linkage to the transmission and remove the top transmission cooler line. Cover the line end with duct tape or plug it with a bolt. Cover the transmission cooler connection on the transmission with duct tape. Repeat this procedure with the bottom transmission cooler line. Unscrew the speedometer cable.
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4
Slide a floor jack under the transmission pan, positioning it so that the jack pad rests near the front of the pan. Raise the jack pad until it places very light pressure on the transmission.
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5
Remove the transmission cross-member mount bolt then the bolts that secure the cross-member to the chassis. Slide the cross-member out of the way and remove it. Carefully remove the transmission bell housing bolts, starting from the top center and removing two at a time as you move down the sides. Tap the transmission with a rubber mallet to break it free of the engine.
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6
Roll the transmission backward on the jack and lower it until you have at least 6 inches of clearance between the torque converter and anything in front of it. Slide the old torque converter off.
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7
Fill the new torque converter with at least three-quarters of transmission fluid and lubricate the converter shaft. Carefully lift the heavy converter into place and slide the converter hub shaft onto the transmission input shaft. Press it firmly into place.
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8
Turn the converter clockwise while pushing inward; it may turn a full rotation before you hear a solid thud, accompanied by the converter dropping into the transmission housing by about 1/8-inch. This part is vitally important: continue to turn the transmission clockwise, while pressing in, until it drops and thumps again. Many novice mechanics have made the mistake of neglecting this second turn and drop, only to have the new torque converter eat the transmission oil pump and destroy itself in the process.
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9
Reinstall the TH400 in the reverse order of removal, being careful to keep the transmission tilted slightly back at all times to ensure that the converter doesn't slip out during installation. It can't hurt to turn the torque converter once more before tightening the bell housing bolts. The converter mounting tabs should just brush the flexplate after tightening the bell housing bolts. If the converter wedges against the flexplate, it has slipped out of the transmission during installation. Torque the bell housing bolts to 50 ft.-lbs. and the converter bolts to 35 ft.-lbs. You might consider using blue thread locker on the torque converter bolts to keep them in place. Check your transmission fluid level before and after starting the car.
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Tips & Warnings
Do not forget the second torque converter drop during installation.
