Piston Slap: You (Axle) Tramp!

Timothy writes:

This isn’t a question about any car that I current own, or even a car that was ever mine.

While watching one of my all time favorite shows, “The Rockford Files,” our hero Jim was stuffed into the back of a mid-’70s Cadillac Fleetwood. As the driver dropped it into drive and the Cadillac moved out, I noticed a very peculiar rear-end wiggle. This isn’t the first time that I’ve noticed this in a General Motors vehicle.

Growing up, my parents had a ’81 Chevrolet Caprice coupe and a ’77 Pontiac Catalina coupe, and an ex-girlfriend of mine had an ’81 Pontiac Catalina sedan that did the same thing. (While I love my parents dearly, I’ve never understood why they bought Ford trucks repeatedly, but never ventured into a Ford car.) They all had that exact same low-speed rear-end shimmy.

What the heck is that?

Keep the esoteric Ford fanaticism alive, please!

Sajeev replies:

Timothy,

Any chance you can tell me which episode had the GM wiggle, or show me it elsewhere? I am not entirely sure what you might be referencing, and I have these episodes on my DVR.

Timothy answers:

I knew you were going to ask to see some evidence! “The Trouble with Houston” – season 2, episode 20, at 45:40.

Sajeev concludes:

I thought I had that episode on my DVR, but it was erased along with scores of other unwatched, retro-TV shows while recovering from the worst of Stevens Johnson Syndrome (mentioned previously here). Not that I like to make excuses, but now I’m gonna assume you saw wheel hop, probably of the axle tramp variety.

I think the GM wiggle you’re referring to is the same as the Ford and Chrysler wiggle. Let’s not single out GM; aside from the leaf-sprung Chryslers, they all made soft, oversprung sedans with 4-link, stick axles struggling to put down the diesel-like torque of a low-compression big block V8 on whitewall tires.

Four links can control unnecessary axle wiggle with a Panhard rod, torque arm or a Watt’s link configuration. Even the last Panthers performed somewhat OK with the Watt’s link. I doubt any of this was in the bad guy’s obligatory, black Cadillac Fleetwood 75 (“The Rockford Files”) or Lincoln Continental Town Car (“Starsky and Hutch”). Add the sloppiness of non-gas charged shocks and every 1970s bad guy makes a wikkid-bad escape from the crime scene with ease.

It was acceptable to have a dancing rear suspension back then: Mercedes still couldn’t penetrate our country’s demand for Panther Love, for lack of a better phrase, and nobody woulda bought a Toyota with some funny “L” emblem back then.

It was a simpler and stupider time when Cadillacs were the only way to rule the highways!

[Image Source: Shutterstock user Fortgens Photography]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.