good day

I have a 73 Datsun 1200 pickup with a heavy vibration. the vibration is only when I gear to 4th gear and when I'm at speed and i put the car to neutral its even worse. I've fitted a new prop shaft, done the t-housing bush,put a new clutch, replaced all the mountings, put new tires, new inner and outer tie rod ends, everything has been replaced but the vibration is still there. I've spend thousands on the car but the vibration is always there.
I've even tried to re angle the shaft but that also did not work.
is there any thing else that can cause this heavy vibration???
I don't know what else it could be.
I'm not to sure if my Datsun is a 520, 521,320 or so!!
Does some one know what else can be wrong??

When you were going through your drivetrain, were the driveshaft u-joints pretty bound up? If so, they could have helped make the holes for the shafts elliptical, especially if it is aluminum. I'm not familiar with this truck, but what I refer to would be like the output shaft from the transmission. That hole where the driveshaft plugs in could be worn and misshaped. So the transmission shaft bounces around inside. Do you have any leaking seals on your transmission?

Another place to look is wheel bearings, but those wouldn't be gear specific so much I think. Speeds would shine a light on bad wheel bearings. Have you checked your wheels for play?

Thinking back over the years; if you remove a drive shaft, and do not put it on exactly the same way it came off, you can have that problem. Just a little 'food for thought'. No particular reference to this vehicle. All vehicles I have ever worked on. Sometimes no difference. I doubt the wheel bearings. Has the vehicle been checked for alignment? I doubt that is the problem though. If it is out of alignment, you would probably notice it will go to the right or left when you let loose of the steering wheel. Sounds like a drive shaft situation to me. Unbalanced wheels can cause problems. You would have figured that out by now though. Just a thought.