Two problems related to rear suspension shock absorber have been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
Vehicle vibrates severely at speeds above 55. Vehicle shakes when brakes are applied. Dealer has advised potential problems with front hubs, rear shocks, wheels and tires. Vehicle has been to dealer three (3) times since 08-25-99 for diagnosis and repair of problem, but as of 09-10-99, the problem of overall major vibration hasn't been resolved.
There is a rattle underneath the rear of the vehicle, the dealer has tried to remedy the problem by the following: changed the power steering and transfer case fluid, replaced the shock absorbers, the spare tire jack hoist, and hoses, however the problem still exists.