Steering wobble

[79vette]

I have an 86 K5 on an 82 10 bolt front axle. 33" Wrangler MTRs.
Ball joints, tie rod/rod ends, wheel bearings, steering box brace all new about 10k miles ago, and the truck has driven fine for about a year and a half since I did all that work

There's a huge bump in the road on my way to work that I hit at 35mph and usually produces a minor oscillation in the steering that damps itself out after a second or two (5-6 minor oscillations)

Yesterday I checked the tires and noticed they were all badly under inflated (26 psi) so I aired them up to 35. When I hit that bump this morning I nearly wrecked the truck. It was instantly the worst death wobble I've ever experienced, and despite immediately applying gentle braking and maintaining as much steering control as I could the truck almost went off the road into a parked semi trailer. I went around the block and hit the bump again mich slower at 25 mph and got the same thing, but it was easier to regain control due to the lower speed.

When I get home tonight I'm going to jack up the front end and check for slop in the wheel bearings, ball joints and tie rods, check the toe in, check for loose/worn suspension bushings, loose steering box bolts/frame cracks, loose U bolts, visible tire damage/broken belts, and anything else I can think of. I think whatever the problem is has been there for awhile and was masked by the low tire pressure, but I don't know how to identify it.

I'd appreciate any suggestions on what to look for.