Shaking at speed.

Reply #15 – February 09, 2009, 07:17:49 PM

Well, I don't know...it could be. My only real experience with a shimmy like what you're describing was with the convertible. Actually a year before I even owned it, I took it for a test drive and the shimmy was very noticeable. I just chalked it up to the conversion...but after buying the car the shimmy was definitely more than the roof being cut off. It was absolutely repeatable, between 25-40 mph, never before or after those speeds. Sometimes it was horrible, sometimes it was bearable, but it was always there.

So three years later I dropped the new 5.0 in, and that was what will now be known forever as The Summer of Five Transmissions™. One of the AOD's (#3...and #5 also, the one still in there) ended up being from a Mark VII, with the longer Lincoln tailshaft which I didn't know about until, naturally, it got installed.

Bear with me...the point is almost here.

So I took the stock driveshaft up to a shop to have it shortened, after getting the required measurements. A few days later when picking it up, I was asked by the shop owner if the car had a pr0nounced shimmy. I said, "Hell yeah it did, how did you know?" I just figured he found a dent or something, but he mentioned that there were three large weights on the shaft. According to him, if a driveshaft is perfectly balanced, there is no need for any weights at all. Now I can see that with a custom driveshaft like mine, but for all those production cars that would be impossible. So the tacking on of weights was not only necessary but justified on a mass-production scale. Still, this is THREE weights...that's a lot, even for stock. One or two were the norm.

I'm sure they're factory on your driveshaft. And I'm sure that, at one point, they might have been necessary. But all these years later, with everything wearing in (and out) I'm not so sure. If you could get it balanced that would tell you absolutely everything you'd need to know, one way or the other.

Alternately, you might be able to rotate the driveshaft 180 degrees and see if that helps. Obviously that's the free solution.

Shaking at speed.

Reply #16 – February 09, 2009, 07:35:52 PM

Mine was balanced a few months ago.No weights.

Shaking at speed.

Reply #17 – February 09, 2009, 07:36:13 PM

Interesting... So flip it and see what happens. I may try that when I replace the seal. I've been leaking a little fluid from that area. Thought it was originally coming from the pan but seems to be the seal.