Piston Slap: Pontiac’s Grand portal enhancements?

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Flickr/Chad Horwedel

Tony writes:

I have a 1974 Pontiac Grand Ville convertible, with the 455. The power-window motors for both front windows need to be replaced. One is now stuck 4 inches from the top, the other one is really slow and the doors sag.

  1. Can the hinges be adjusted to reposition the door or do I have to get new hinges?
  2. How do I replace the window motors? The rear windows have a cover I can remove to replace the rear window motors, but the front ones don’t have this cover. There is a large hole in the door that I can reach in, but it’s really awkward. I can’t see what I am doing.

I’m not a gearhead, but I try to do as much work on the car myself. Basic things like fluid changes, tune ups, brakes, some part replacement I can do, but I have never had to work on the doors/windows until last summer.

Sajeev answers:

You can absolutely do this work yourself! Well, you probably need another set of hands for the door hinge repair, but that’s your call. And while a set of factory shop manuals is unnecessary for these tasks, this is a good time to mention their intrinsic value in classic car ownership.

With that in mind, let’s answer your questions:

  1. Neither of your intended repairs likely apply here—instead you’ll replace the door-hinge bushings. These are sacrificial parts in all(?) door hinges that wear out over time. Dorman products makes a replacement kit, and a good video detailing the process is found here. If you undertake this and are not happy with the end result, the hinge can be loosened/realigned/tightened to the body either by yourself or a local body shop. But odds are that new bushings are all you need.
  2. Power-window motors are somewhat easy to change, as three bolts attach the round “head” of the motor to the window regulator assembly. But GM often refuses to give easy access to the bolts, so you may want a smartphone-enabled endoscope to find the location of each bolt. This video (intended for G-body vehicles) suggests cutting holes in the door panel to access bolts you might not be able to reach. It has merit, as I ain’t too proud to admit I’ve done this before. (I used progressively larger drill bits and a rotary grinding tool to carve out a hole big enough for my socket wrench.)

One last point—I believe you are indeed a gearhead! You just need the motivation to leap from basic maintenance to full-on body and interior restoration. Finding local mechanics to undertake these labor-intensive (and less-profitable) tasks is often difficult, but they are something any skilled hobbyist can tackle themselves. All it takes is sourcing the right parts (and repair videos!) online, mapping out all the little steps that need to happen, and taking the plunge yourself.

Trust me, it’s worth your time to make this happen. Best of luck!

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com, give us as much detail as possible so we can help! If you need an expedited resolution, make a post on the Hagerty Community!

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