Hood Shake Fix!

There is a fix available from GMC, which is basically just a couple of rubber bumpers that fit underneath the back of the hood. You might want the dealer to print out the TSB and instructions for you if you\rquote re going to do it yourself, because the parts don't come with instructions on exactly where to place them, and my instructions aren't always the clearest. You'll also need some weatherstrip adhesive (available at any parts store). The part number for the bumper is 458306. You need two. I had the same problem after I installed my hood deflector, and this solved it. The bumpers (used as hood stops) are supposed to hit the little raised sections of the inner sheet metal of the hood that are above the cowl. Measure 8.5 inches along the lower cowl panel from the inboard side of the front fenders, and center the bumper on this measurement. Do this for each side. The instructions say to scuff the paint with some 400 grit sandpaper before applying the glue - I drew an outline of the bumpers on the cowl once I got them placed correctly, then masked it off and scuffed the paint just enough to take the shine off of it. Then I cleaned it with some wax remover. You'll want to make sure the bumpers clear the rear lip of the hood, where the outer and inner sheet metal join. If that lip rests on the bumpers, the hood will stick up too far.

Bumpers go on top of cowl, under hood

One other thing - at the same time I put in these bumpers, I replaced the left and right hood hinge weatherstrip, and the weatherstrip that goes along the length of the cowl under the hood. With the bumpers, the back of my hood is now very solid. I have the Lund hood deflector, and I HAD that problem when I first installed it, but then I installed the necessary bumpers (from TSB #91-10-20) at the rear of the hood which completely eliminated the hood bouncing. For more info, look in the archives for an email from Jeff Stabell sent to the list on 6/20/96, with subject line The Hood Bouncing part number!