The vibration could be many things. The first thing to do is to isolate
what is causing the shake.
Put in Neutral and rev engine, if no vib, jack up under dif and run through
gears and note if vibe still starts at 35 mph and still gets worse, then see
if it starts at a certain rpm in different gears. If it is always 35 mph no
matter which gear, the vibe is after tranny. Then put one wheel on the
ground and make it vibrate. Which gear and what rpm and what speed. Then
do the other wheel on the ground. That will tell you if one wheel is out of
balance or if it is the drive shaft or a bent wheel etc. If it is one wheel
more than the other, swap both rear with front wheels and try again. Any
difference?
So far, you have spent nothing, drank a six pac and learned a lot. Some
times there is a slight bulge on a tire that you can hardly notice but will
make a good shake. If you can't make it vibrate with the above, then you
know it is in the front of the car and with the tires rotated, drive it and
see if it still shakes and if the shake is different. You might also try to
put the spare on one front and then the other front and see if that changes
the vibration.
By then, you are out of beer and at least know where the vibration isn't
coming from.
Cheers,
Bob in San Diego
Robert D. Gardner
Gardner Productions LLC
Film and Video Production since 1978
619-460-1000
www.gardnerproductions.com
On Tue, Dec 8, 2009 at 11:49 AM, Edward Perez <eap2140@yahoo.com> wrote:
> My car is experiencing a vibration at 35mph or so. It worsens if you
> try to go any faster. The mechanic's thoughts on this are that the
> drive shaft is at a severe angle causing the u-joints to bind. I have
> a
> 78 Midget with a 1275 and Datsun transmission. We recently installed
> the rebuilt motor (it was pulled and installed with the tranny). Has
> anyone experienced anything like this? Could there be an alignment
> issue with the way it was re-installed? The suggestions are to look
> for a lower transmission rear mount and install wedges at the axle. I
> found the 2 degree wedges at Summit and I'm wondering if I need 2 or 4
> degrees. Do I need to pull the engine and trans to install a lowered
> rear mount? The other thing he noted was that the yoke is bottomed out
> on the rear of the transmission leaving me no play for the suspension.
> Potentially causing bearing wear. My first course of action will be to
> take the drive-shaft to the shop for evaluation and shortening.
> Thoughts on how much I should shorten it? The U-joints are an unknown.
> They flop around loosely when the drive shaft is out of the car. Not
> sure if they are supposed to be firm. There is no lateral slop in them.
> This is never-ending. All I want to do is drive my freakin' car.
> _______________________________________________
> ************************************
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