Rear suspension problem

[Gud T.B. Blown]

i have a '73 mach 1 and when i go over rough pavement of slight pot holes the rear suspension bounces for lack of a better description. to give you an idea i was went around a flat curve on a residential thruway at @40 mph and drove over a depression (not even a pothole) in the pavement and the rear end bounced and jumped a good foot to the left. surpised the heck out of me.
when i got the car i changed the rear springs with factory like replacements, the car also has air shocks, and BFG drag radials. i had a set up similiar to this on my '71 except the drag radials and never had this problem. i have less than 600 miles since i replaced the springs etc... is it a settling issue? any ideas.

 

[iskwezm]

get rid of the air shocks,that your problem.I used to have them on mine and just recently put them back on for a band aid fix for sagging springs,even though I hate them.

Get a good gas charged shock and youll notice the jumping will go away.

 

[Sicarius428]

Get some softer springs and some better gas shocks. I suggest Koni shocks... KYB tend to be a tad too stiff.
Kevin

 

[Gud T.B. Blown]

Get some softer springs and some better gas shocks. I suggest Koni shocks... KYB tend to be a tad too stiff.
Kevin

softer than stock? the only question i have regarding the air shocks is that my last mustang had the same set up, albeit older springs, and i didn't have this problem.
is it because the springs are new and haven't been fully broken in yet?

 

[Hack]

My convertible is really rusty and I had this problem. Then I added subframe connectors and the problem went away. I'm thinking that the issue on your car is probably the shocks like stated above, though. It sounds like your car is in much better condition than mine.

I thought I should post this anyway, because some readers might have the problem/cause that I did.

 

[68 Coop]

How many lbs are you running in the shocks???

 

[Gud T.B. Blown]

How many lbs are you running in the shocks???

i don't recall offhand. i'm going to have to check when i get home tonight. i do know that i only put in enough air to clear the rear tires.

 

[mdjay]

The pounds are not going to matter much. There is no dampening.

Air shocks are not good for much except raising the car a little bit. It helps to split the air valves a little. You can raise the rear of the car other ways to get more clearance if needed.

Rear sway bars can also create this condition if you have the clamp style and have them too tight.

IMO the Classic Koni's are more stiff than the KYB's thought! However I have my Koni's adjusted toward the higher side of dampening!

QA1 just came out with some new bolt in rear shocks that are two way adjustable as well.

 

[mustangdave]

I found that ceap Autozone shocks work well with new and/or stiffer springs. They are SUPER inexpensive gas shocks that give a nice ride on the street. Also make sure all of the bolts are tight holding the springs (frt., axle, and back). If something is loose, your whole rear end could be shifting...well, the cars, not yours.

 

[Sicarius428]

Sorry I just assumed that you had aftermarket springs. My KYBs just seemed to buck more... Koni's always felt like they were better at dampening... maybe its just me.
Kevin

 

[Gud T.B. Blown]

I found that ceap Autozone shocks work well with new and/or stiffer springs. They are SUPER inexpensive gas shocks that give a nice ride on the street. Also make sure all of the bolts are tight holding the springs (frt., axle, and back). If something is loose, your whole rear end could be shifting...well, the cars, not yours.

thanks for the tip. i'll check the bolts and retighten as needed and autozone is just down the street from my house.

 

[mustangdave]

Also check Advance Auto. Iirc I paid $60 for four shocks.

 

[reenmachine]

I assume you installed all new leaf spring eye bushings/shackles when you replaced the springs?

 

[Gud T.B. Blown]

I assume you installed all new leaf spring eye bushings/shackles when you replaced the springs?

that is correct.

 

[mdjay]

Sorry I just assumed that you had aftermarket springs. My KYBs just seemed to buck more... Koni's always felt like they were better at dampening... maybe its just me.
Kevin

Yep. More dampening will actually feel stiffer. Less dampening will just let the spring bounce.