major body shift during acceleration or deceleration

bruce bennett · Post by **bruce bennett** » Tue May 01, 2007 10:27 am

Ok.
I have a "77 Spyder convert.
It's a junker, I'm not restoring it. it's way to far gone to do that. I'm turning it into a street legal racer or as close to that idea as I can come to on a limited buget.

the problem as outlined in the subject is simple, the solution has been elusive to say the least. I'm an older ASE certified mechanic and things that I thought would surely be the issue turned out not to be.
Whats been done so far is;
new floorpans, ( originals were rotted beyond any hope of repair) along with extensive additional braceing in and around the trailing arm gussets.
also, I added 2" box tubing from the front subframe rails to the back frame rails and then added lots of 2" box tubing to the trailing arm gussets completely boxing them in.

all new front suspension componants includeing steering linkages.
new motor and tranny mounts.
completely rebuilt driveline with all joints replaced.
all new brake system from booster out to each wheel includeing the wheels.

This year was planned the rear suspension work which is admittedly a tad worn. but nothing appears loose.. which first thought was the panhard bar bushings but they appear to be tight. then I thought maybe it's a weld somewhere.
but nothing shows up. even under black light testing.
I do have the upper rear shock bushings are moving just a bit when the car is bounced hard enough.
but surely thats not what would cause such a major body shift.. this thing feels like it's about the lose the entire rear axle and I'm not talking about" in the corners". I'm talking straight line driving while trying to maintain a steady speed.

If you hold a speed , say 50 MPH, then just change your gas foot from the slight accell. to the slight decell. modes.. then it feels like the whole car is about to swap ends on you. and this gets worse with any increase in speed. but it does it at any speed. even below 10 MPH. just less frighteningly. but the car still appears to be tight in all respects upon visual inspection. ??

any suggestions would be greatly appreciated.

So Cal Mark · Post by **So Cal Mark** » Tue May 01, 2007 10:49 am

one or both of the rear end links have bad bushings.

bruce bennett · Post by **bruce bennett** » Tue May 01, 2007 10:52 am

So Cal Mark wrote:one or both of the rear end links have bad bushings.

while they are scheduled for replacement this summer..
They "appear" to be tight.. they don't move when pulled or pushed and even whne the car is bounced they don't do anything other than their normal job as far as i can tell.

whats the tell-tale signs to look for?

HOLLYWOODSPIDER · Post by **HOLLYWOODSPIDER** » Thu May 03, 2007 2:51 am

Telltale sign is exactly what you describe. I'd do the lower and upper rear trailing arms as well as the panhard rod.

I just went through exactly the same symptoms you describe. Lower trailing arms couldn't be budged by hand, but sure enough, they proved worn once I'd removed them. Unless you can put about 700 lbs force on those bars, you can't tell if they're worn.

bruce bennett · Post by **bruce bennett** » Thu May 03, 2007 3:31 pm

Thank you , I appreciate the input.
I was starting to think that my differential needed rebuilding as well.

bruce bennett · Post by **bruce bennett** » Wed May 09, 2007 3:20 pm

Alright! My new trailing arms and panhard bar arrived today.. got my standard shocks.
Now I'm waiting on my Sway bars

now, I'm still hopeing for anyones opinion on the Aussie Company called Dobson Springs. They make a nice looking high rate "blue" spring that some say is great.. but I haven't found anyone here in the states that can back that up.

bruce bennett · Post by **bruce bennett** » Mon May 21, 2007 5:50 pm

Found the source of the original problem, one of the upper short "link-to-body" bolts was bent pretty badly. Had to order the correct thread bolts from England.
But everything feels MUCH better now. great straight line acceleration and braking.

Can't wait to add my new front and rear sway bars and shocks

mdrburchette · Post by **mdrburchette** » Mon May 21, 2007 8:46 pm

I'm glad you found the problem! Let us know how the new parts work out.

perthling · Post by **perthling** » Tue May 22, 2007 6:45 am

I've seen those Dobson (Dobinson?) springs on eBay but beffore that I had never heard of them. Major spring mnfrs down here in Oz are Kings and K-Mac (among others - but they are the main ones I have come across who fit out Fiats). I'm sure Curly can name a few more...

bruce bennett · Post by **bruce bennett** » Tue May 22, 2007 5:55 pm

perthling wrote:I've seen those Dobson (Dobinson?) springs on eBay but beffore that I had never heard of them. Major spring mnfrs down here in Oz are Kings and K-Mac (among others - but they are the main ones I have come across who fit out Fiats). I'm sure Curly can name a few more...

Yep, thats where I first saw them too...
But now I can't find them anymore?
wonder why?

whats your impression of the Kings and the K-Macs?

any links to these companies would be greatly appreciated.

perthling · Post by **perthling** » Tue May 22, 2007 7:29 pm

Try http://www.kingsprings.com.au and http://www.kmac.com.au .

major body shift during acceleration or deceleration

major body shift during acceleration or deceleration

Installed the new rear suspension!