I had a post awhile back about bad vibration in my rear of my 65 Lark and most suggested it is probably the driveshaft out of balance.Anyway I tried two solid driveshafts I have and the second one almost did away with it but not completley.So I had a third driveshaft that has the rubber vibration damper built into it and it is all smooth now at all speeds. My question now is my 65 service Manual says they used the rubber inserts in the driveshafts for the auto cars and the solid ones for the Manual cars.Mine is a 4 speed manual so my question is why the differance between manual and auto driveshafts and is there going to be a problem running a auto shaft in my manual car.I do not see a problem but the factory must have done this for a reason and if you happen to know why please enlighten me.............Thanks to all who helped diagnosis the problem in my original post...........
More than likely the rubber dampened shaft often refered to as a two-piece shaft (but its not) was not only the correct length fitment wise for your car but has good u-joints and still retains a good factory balance. As fas as what you call a 1pc. "solid" shaft (which is actually a hollow tube) may have not been the exact correct length, out of balance. slightly bent, or had loose universals. Any of these conditions could cause your cars vibration problems. When a shaft is installed in the vehicle in what is refered to as a "riding position" (rear end supported/not hanging) the trans slip yoke should have no more than 3/4in. to 1in. showing between the seal lip and the slip yoke casting. Also the rear u-joint must have the clips installed on the caps at the rear pinion yoke (3RL style) for centering and other purposes. The auto or manual shafts can be used in either application as even automatic GM cars had the rubber dampened shafts installed. I've seen more non-dampened shafts in 4 speeds and higher horse/torque cars. The only thing you have to be concerned with on the dampened shafts is the shaft yokes twisting "out-of-phase". This occurs when the 30+ year old rubber inserts start to loose their internal "grip" if you will and allow the rear part of the shaft to slightly turn. This normally causes the shaft to "shrink" or shorten effectively pulling the trans yoke out of the transmission. There are many different factors that can cause a driveline/driveshaft vibration but I'll reserve that long list for another post.... Tim
