Transmission problem
1987 GMC C1500 V8 Two Wheel Drive Automatic
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step by step guide on how to remove transmission from truck

Turbo-Hydramatic Transmissions
Super Turbine 400/THM400/3L80/3L80HD
Rear 2-Wheel Drive

1.Disconnect the battery ground cable.
2.Disconnect the detent cable at the carburetor.
3.Raise and support the truck on jackstands.
4.Remove the driveshaft, after matchmarking its flanges.
5.Disconnect the speedometer cable, downshift cable, vacuum modulator line, shift linkage, throttle linkage and fluid cooler lines at the transmission. 6.Remove the filler tube.
7.Support the transmission and unbolt the rear mount from the crossmember. Remove the crossmember.
8.Remove the torque converter underpan, matchmark the flywheel and converter, and remove the converter bolts.
9.Support the engine and lower the transmission slightly for access to the upper transmission to engine bolts.
10.Remove the transmission to engine bolts and pull the transmission back. Rig up a strap or keep the front of the transmission up so the converter doesn't fall out.
11.Reverse the procedure for installation. Bolt the transmission to the engine first (34 ft. lbs.), then the converter to the flywheel (50 ft. lbs.). Make sure that the converter attaching lugs are flush and that the converter can turn freely before installing the bolts. Tighten the bolts finger tight, then torque to specification, to insure proper converter alignment.