Greetings 2RED,
'Death Wobble' implies steering, but since we're all remote the more you spell out exactly
what you are experiencing the better we can visualize the systems interacting with each other.
Please elaborate on the wobble. More specifically:
1) Did you feel the wobble as side-to-side shimmying of the steering wheel? Or was the
vibration fed back to you via the brake pedal? Or both wheel & pedal vibrating?
2) Was the truck vibrating prior to the brake work, and the brake job was performed in order to cure that?
Or was the truck vibration-free before the repair effort, and the vibration only showed up after the new parts were
installed?
3) What's the year, make, & model of the GMT400 that you are working on? Bonus points if your glove box still
has the original RPO listing affixed to the inside, and you can tell us the brake RPO code? (JBn or JDn) We have
talent in the forum that are seriously familiar with the ins & outs of each brake combo.
4) What brand brake parts did you purchase/install? The brake gurus in this forum have 'proven good' parts
recipes that we can compare your parts list against, on the chance that your truck is dealing with new parts
that would have run afoul of the QA processes back in the day.
5) When working on prior 'vibrating brake' issues, I've been humbled by working on a brake issue that *must* be
happening in the front, and only after I spend lots of time unable to fix something that isn't broken, I'll go out back
and find the problem there. :-( And on the next vehicle, the exact opposite happens. Phooey!
So let's figure out if the root cause of the problem is in the front or rear of your truck. Assuming that your mechanical,
cable-operated emergency brakes are working, accelerate up to/slightly beyond the 'death wobble' speed, and now slow
the truck using ONLY the emergency brake pedal. IF the problem still shows while you are doing this, then you have to
double check everything in the back until you find/fix the issue.
On the other hand, IF by slowing down the truck using only the rear shoes via the emergency brake cables and there's
no wobble at all, then the problem has to be in the front. Either bad new brake parts (brake parts as perpetrator) -or-
the brake parts are good, and they are a victim of excess play somewhere in the front suspension and/or steering
system.
Please perform the test in #4 and let us know what you find. And give us as much detail as possible on the rest of
the questions. Fortunately the GMT400 brakes can be made to function quite well, but it takes a lot of attention to
detail in order to achieve this.
Best of luck. Happy Hunting --
