I just removed a seized L94 and 6L80 trans together as a unit, and wanted to describe the process I used in case it helps others. 2011 Yukon XL Denali AWD. My engine was seized, and I knew it wasn't a bearing issue because the motor wouldn't turn much at all, and it was a hard lockup. Since I couldn't access the Torque Converter bolts to separate the engine from the trans, I pulled the whole assembly as one unit.
I started by removing the battery, bumper cover, radiator support, radiator, oil coolers, and evacuating the ac system. This provides better access to the motor and is necessary to remove the motor and trans together when you get to that point. I then removed the air filter, disconnected the electrical harness, and removed the coil packs on top of the valve covers. Then I removed the alternator and PS pump, and the mount for these accessories. Also removed the ac compressor and mount. I left the trans and engine oil cooler lines intact but made sure they were routed above the lower panel where the radiator and other coolers sit. I removed the metal bracket that's mounted on top of the two bellhousing bolts at the top to the bellhousing, and the grounding strap on the left head near the brake master cylinder. I removed the bolts holding the motor mounts to the frame crossmember.
Then I worked on the underside. I drained the motor and transfer case fluid. Then I disconnected the driveshafts at the axle end and removed them. I had to remove the front sway bar to get the front driveshaft out, but didn't have to disconnect the links to the lower control arms. I separated both exhaust downpipes at the exhaust manifolds, and disconnected the shift cable at the trans. Then I removed the crossmember and trans mount, followed by removing the 6 bolts holding the transfer case to the back of the trans. Had to lower the back half of the assembly a bit to get to the top bolts but was able to pull the Transfer case back and out of the truck. Then I removed the metal temp shield from the side of the trans and disconnected the electrical harness to the trans. Disconnected several sensors on the bottom of the engine. and then went back to the top to rig the engine hoist for the pull.
I attached a chain to the unused threads above the exhaust manifold at the center of the block (between the middle two cylinders on each side of the engine. This is not quite at the center of gravity of the while assembly, but you can lift the unit by pushing down on the front of the engine from the front. With a helper, we lifted the motor to clear the front axles and steering rack, pulling down of the engine to keep the trans clear of the crossmembers etc. and hauled the hoist and motor assembly forward until it cleared the truck.
Splitting the trans from the motor was relatively easy, and amazingly the torque converter didn't make a mess. I removed the TC from the flex plate using a box spanner, and then mounted the motor on an engine stand for teardown. Found the #1 piston missing completely (i.e. in the oil pan) and the #1 rod fractured and the source of the locked crank. The big end was still on the crank journal though, so this appears to be a piston/wrist pin/rod failure. 225K on the motor - no sign it was ever opened or removed previously.
Removal required about 12-15 hours of effort - could probably do it in less than 10 if I had to do it again.
I started by removing the battery, bumper cover, radiator support, radiator, oil coolers, and evacuating the ac system. This provides better access to the motor and is necessary to remove the motor and trans together when you get to that point. I then removed the air filter, disconnected the electrical harness, and removed the coil packs on top of the valve covers. Then I removed the alternator and PS pump, and the mount for these accessories. Also removed the ac compressor and mount. I left the trans and engine oil cooler lines intact but made sure they were routed above the lower panel where the radiator and other coolers sit. I removed the metal bracket that's mounted on top of the two bellhousing bolts at the top to the bellhousing, and the grounding strap on the left head near the brake master cylinder. I removed the bolts holding the motor mounts to the frame crossmember.
Then I worked on the underside. I drained the motor and transfer case fluid. Then I disconnected the driveshafts at the axle end and removed them. I had to remove the front sway bar to get the front driveshaft out, but didn't have to disconnect the links to the lower control arms. I separated both exhaust downpipes at the exhaust manifolds, and disconnected the shift cable at the trans. Then I removed the crossmember and trans mount, followed by removing the 6 bolts holding the transfer case to the back of the trans. Had to lower the back half of the assembly a bit to get to the top bolts but was able to pull the Transfer case back and out of the truck. Then I removed the metal temp shield from the side of the trans and disconnected the electrical harness to the trans. Disconnected several sensors on the bottom of the engine. and then went back to the top to rig the engine hoist for the pull.
I attached a chain to the unused threads above the exhaust manifold at the center of the block (between the middle two cylinders on each side of the engine. This is not quite at the center of gravity of the while assembly, but you can lift the unit by pushing down on the front of the engine from the front. With a helper, we lifted the motor to clear the front axles and steering rack, pulling down of the engine to keep the trans clear of the crossmembers etc. and hauled the hoist and motor assembly forward until it cleared the truck.
Splitting the trans from the motor was relatively easy, and amazingly the torque converter didn't make a mess. I removed the TC from the flex plate using a box spanner, and then mounted the motor on an engine stand for teardown. Found the #1 piston missing completely (i.e. in the oil pan) and the #1 rod fractured and the source of the locked crank. The big end was still on the crank journal though, so this appears to be a piston/wrist pin/rod failure. 225K on the motor - no sign it was ever opened or removed previously.
Removal required about 12-15 hours of effort - could probably do it in less than 10 if I had to do it again.
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