malibu@hound.UUCP (K.KRUSINSK) (01/16/86)
Here's one for all the Z fans out there. There must be about a billion of you. Here's the deal: My recently purchased 1978 280Z has developed a nasty vibration in first or second gear while the car is under acceleration (From a stop or near standstill.). It also occasionally makes a single loud "thunk" starting from a stop. All this noise originates from the rear end (apparently) so I figured the problem is in the axle half-shaft U-joints. I can't isolate the problem, though, because I can't identify any bad U-joints by inspection. All four are tight, show no free play, and otherwise look fine. If any of you Z people have had a similar problem, I'd like to hear what the source of the trouble was. I'd rather not pull out those axle shafts in this gorgeous 20 degree N.J. weather only to find the problem isn't there. Thanks for the help. Kurt Krusinski (201)949-4429
bruce@dciem.UUCP (Bruce Ferguson) (01/17/86)
stuff more I have occasionally found that U-joints look fine upon inspection , but can never the less be kaput. (brilliant statement). What is required, is to torque the suspect joint quite firmly, and look for any movement of the cross-piece in the bearing cup. If only one end of the cross has a failing bearing, it is possible that to a non-strong-arm inspection, all will appear well. Obviously under accelleration (or strong engine braking), the torque on these units is considerable, and so should it be when you are snooping for a bad U-joint. Perhaps a helper with a wrench on the front crankshaft pulley bolt, 1st gear, and the handbrake set will reveal something. It is also possible that the higher torque multiplication in the lower gears, causes the drive line to twist in its mounts enough for some thing to touch where it could make a noise (ie.the exhaust system). This might point to weakening engine or driveline mounts, or an improperly positioned exhaust system. Maybe this would also be revealed by winding-up the driveline with a wrench, as described.
marauder@fluke.UUCP (Bill Landsborough) (01/20/86)
In article <1604@hound.UUCP> malibu@hound.UUCP (K.KRUSINSK) writes: > >Here's the deal: My recently purchased 1978 280Z has developed a >nasty vibration in first or second gear while the car >is under acceleration (From a stop or near standstill.). >It also occasionally makes a single loud "thunk" starting >from a stop. All this noise originates from the rear >end (apparently) so I figured the problem is in the >axle half-shaft U-joints. I can't isolate the problem, though, >because I can't identify any bad U-joints by inspection. >All four are tight, show no free play, and otherwise look fine. Two things. Put the car against an immovable object and while you or a friend tries to drive through the immovable object the other is looking and listening for the area of noise. Another possible "suspect" is loose motormounts which allow your engine to rotate more than normal under hard acceleration and the exhaust pipe or manifold is first thumping and then vibrating against the frame. Bill Landsborough ---- "Love is patient and kind; love is not jealous or boastful; it is not arrogant or rude... Love bears all things, believes all things, hopes all things, endures all things." 1 Corinthians 13:4-7