Vibration when pulling away

[NIGE1961]

 Hi there new to this site i have a 1961 cadillac coupe deville i have a problem when i pull away i get a brief vibration coming from the rear its very odd as it is not present when i'm driving just when i pull away  can anyone help thanks Nigel

[Dave Shepherd]

Loose trans mounts, grounded exhaust, more commonly u joints or the centering ball in the double Cardan joint in the drive shaft.

[The Tassie Devil(le)]

G'day Nigel,

Have a good look at the ball joint at the top of the differential, and the rear end bushings.

My old '60 CDV did what you describe, and I chased it everywhere, and the vibration/shudder would never happen in reverse. 

I never did replace the Bushings, but the Ball Joint was totally work out, and it was this that allowed the diff pinion angle to go out of alignment.

Bruce.

PS.   You have an email.

[62droptop]

sounds driveline related

there is no double cardan in the 61, it is a 2 piece driveshaft with a hanger bearing

my 62 had a shudder when i stood on the gas taking off,only when i had the rear end raised up a wee bit on the air shocks
the upper ball joint was a bit loose so i changed it
the ball joint holds your rear axle in place side to side and holds the pinion angle correct
if it break while driving, the rear axle can go all screwy and the tires may contact the body and skirts, danmage drive shaft etc
they are not hard to install, just take some patience
and if it has no grease fitting on it and is rivited in to the a arm, i would just replace it anyway for safety sake
could just be a u joint on its way out too

also a collapsed trans mount or misaligned driveshaft, a lot ot times due to center bearing taken out and shims not put back in
butthat will give vibration more at speed

[dplotkin]

I have a 63 Impala with the same driveshaft, X frame & center bearing. If you change the ride height, up or down with air shocks, new springs, or weight in the trunk or elsewhere, you will change the pinion angle. The two angles, from the trans to the bearing & the bearing to the pinion have to be nearly the same or you will have a vibration as you pull away. the bigger the difference in the angle, the worse the vibration will be and the longer its duration. (it never goes away, it just becomes so fast you don't feel it as much).

Having said that, especially if you have not changed the ride height it can also be a failed center bearing. The bearing is incased in rubber. The rubber eventually fails (helped by oil leaks that soak the rubber, abusive use (not likely in your case but I blew a lot of these in the high school parking lot as a kid), and, if you put the car in the air to change springs and let the rear hang too low you will pull the rubber out of the housing. The center bearing is cheap & not hard to change.

Dan

[NIGE1961]

Hi there thanks for all your comments looks like i'm going to be busy in the garage over the next few days or weeks,
i now have a list of things to check, i have fitted air shocks as the old shocks were worn out so i thought that would do the trick but made no difference so ruled that one out.
i did think about the top ball joint on the axle but does look newish as the rubber boot looks very clean but i will re check this again.
Only had the car since Jan this year so been doing little jobs but this one is one that has been very annoying as some people who have been in the car always say "what was that" so got to get it sorted
i will keep you updated
Nigel
trying attach photo if i can