DIY Network

Diesel Transmission, Clutch Removal and Replacement A diesel-repair student tackles a full-scale transmission job. From "Trade School" episode DTRS-401

Diesel-repair student Chris Barnes, with the help of instructor Darrell Wayne DeBoer, tackles a full-scale transmission job and clutch replacement on a semi truck. First he has to pull the transmission in order to inspect and replace the clutch and flywheel. He’s done work like this before on cars, but everything on a semi is bigger — and heavier.

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Figure A

Steps:

1. To get at the clutch, Chris will first have to remove the 700-pound transmission. He removes an air tank, which feeds the truck's brakes, to give him more room to work underneath the truck. Then he disconnects all the transmission lines and wiring feeding into the transmission.

2. To support and remove the heavy transmission itself, Chris uses a specially modified hydraulic jack (figure A). After attaching the jack to the transmission, he uses an impact wrench to remove the bolts that secure it to the housing. He pulls the transmission back out of the housing, exposing the clutch, then lowers the jack and rolls the transmission out of the way.

3. Next, using an impact wrench, Chris removes the bolts that secure the clutch. Although not nearly as heavy as the transmission, he again uses the hydraulic jack to lift the clutch out of the housing, exposing the flywheel.

Figure B
Figure C

4. With the clutch removed, Chris inspects it to see if it can be reconditioned, or if it needs to be replaced. This clutch shows signs of excessive wear and rust (figure B) and needs replacing.

5. Before installing a new clutch, Chris has to inspect the flywheel. The flywheel is a heavy metal gear attached to the crankshaft, which transfers power to the drive train, keeping the truck running smoothly while shifting gears. While his shop partner Theo bars over the engine, Chris uses a dial gauge (figure C) to check several sections of the flywheel surface for any defects. The flywheel's surface is slightly warped and needs professional resurfacing

6. When the resurfaced flywheel returns, Chris seats a new pilot bearing into the center of the flywheel with a ball peen hammer and then maneuvers the flywheel back into the housing. Using all of his weight for leverage, he tightens the bolts to a precise setting with a torque wrench.

7. With the flywheel in place, Chris lifts the new clutch into the housing with the jack. He bolts it into place with the impact wrench and torques all the bolts.

Figure D

8. Now Chris has to replace the transmission, fitting the input shaft precisely through the splines of the clutch and into the pilot bearing on the flywheel. This is especially difficult because once the transmission is up against the housing, Chris can no longer see the input shaft, and he has to guide it the last few inches by touch.

9. After a lot of maneuvering, and some help from his instructor, the transmission finally slides into place (figure D). Chris replaces the bolts, and reconnects the wiring, transmission lines and shifter.

RESOURCES :

Wyotech
Website: www.wyotech.com