As our 1988 GMC Sierra trucks continue to age, small problems such as broken ignition lock cylinders will crop up from time to time. Replacing the ignition lock cylinder in your truck is a project that can be done in an afternoon by the average home auto mechanic. A few special tools will be needed, but they are readily available from most auto parts stores, and the cost of these tools won't break the bank. These same tools are used in most steering column repairs done on General Motors vehicles made during the 1970s, 80s and 90s.
Remove the horn pad by unscrewing the small Phillips head screws that attach it to the steering wheel. The four screws are located on the back of the steering wheel. Rotate the small white plastic horn button connector located behind the horn pad to remove the horn wire from the steering wheel.
Remove the 13/16-inch nut that attaches the steering wheel to the steering column. Bolt the steering wheel puller to the steering wheel using the bolts supplied with the puller. Some pullers supply an assortment of bolts; the GMC uses two long 3/8 bolts to clear the steering wheel. The bolts only need to be finger-tight, but they do need to be screwed the same number of turns so they are even on the steering wheel puller. Position the center shaft of the puller in the dimple in the end of the steering shaft. Turn the center shaft of the puller until it pulls the steering wheel off the steering shaft.
Screw the lock plate tool to the steering column shaft protruding from the center of the steering wheel. Position the U-shaped press piece on the lock plate and tighten the tool to compress the spring-loaded lock plate. Remove the circlip that is exposed when the lock plate is compressed using a pair of picks from the small pick set. Slide the circlip up the steering shaft and remove the lock plate tool and lock plate by unscrewing the tool from the steering shaft.
Remove the turn signal cam located behind the lock plate by unscrewing the three lock plate screws and the turn signal lever screw with a medium screwdriver. When the turn signal lever screw is removed, pull the loose lever slide from the turn signal lever so it is doesn't drop inside the steering column. Pull the plastic turn signal cam up over the steering shaft.
Remove the retaining screw that holds the ignition lock cylinder in place in the steering column housing and slide the lock cylinder from the housing. Install the new cylinder in reverse order.
