C1 1959 Driveshaft Vibration

[Dave H.]

I just replaced my T-10 case and rebuilt the innards. The same output shaft was used.

Now I have a brand new problem: a driveline vibration that starts at about 30 mph and gets worse the faster I go. It continues if I push in the clutch and idle the motor. It feels like it's in the driveshaft.

A friend suggested I rotate the driveshaft 180 degrees. Would this be likely to help? Or perhaps an adjustment in the height of the transmission mount?

Can this problem be diagnosed or is the fix trial and error?

Thanks,

Dave.

[Clem Z.]

try turning the shaft 180 degrees first and

make sure the universal joint bearings are seated all the way in the diff yoke

[John H.]

Re: try turning the shaft 180 degrees first and

If you still have a vibration after that, shim the trans crossmember down about 1/4"-3/8" from the frame and try it again; this was a common issue on C1's, and most were built with shims between the top of the trans crossmember and the underside of the frame for that reason. Most of the shims disappeared over the years during trans removal/clutch changes, as people didn't know why the washers were there and didn't replace them when they put it back together.

[Walter B.]

Re: C1 1959 Driveshaft Vibration

Both responses are good, however if that doesn't fix your problem I suggest replacing ujoints and rebalancing the shaft. There is no trial and error, the suggestion on trans mount shims is based on standard engineering design practice with Hooke joints. They are not constant velocity joints, like modern front wheel drive setups. The shims are used to set the trans and pinion angles in the right range so both ends of the driveshaft are in phase.

I would also check to make sure the rear u-joint is seated properly at the pinion.

If your angles are within spec, I suggest new joints and a balance job. Use Spicer u-joints without zerk fittings. I recently did this on my '61 on the advice of a local shop here in town. They suggested the non-greaseable Spicers because they told me they had closer tolerances than the greaseable type. I couldn't be more pleased with their work. Have owned the car since '68 and the driveline has never been smoother. BTW I am running 4.56 gears, so I am spinning my driveshaft a lot faster than most.

Bert Brown