My son-in-law purchased a 92 4 door 4x4 non-dually auto with 162k on the clock. He changed out the u-joints but still has a vibration at about 40mph and again at around 65-70mph. His mechanic told him that maybe the driveline should be balanced or it may be in the transmission (some metal filings when they change the transmission oil). Any ideas? He also wants to do a mild update to the engine but really has no concept of where to start or what makes the most sense in bang for the buck. With a first generation, I don't either. The truck is clean for a 92 and seems to start and run well and doesn't use oil. Any advice from you veterans would be appreciated.