Derek wrote:

Perhaps the problem isn't the rear end, But the front end. Have you also replaced the front springs and bushings. Or checked to see if the sway bar links are shot?

 
all front ent parts are new did complete front end rebiuld

Mustangs are known to have alot of unsprung weight in the rear end, and that makes them bounce a bit.  To add to the problem, lots of people put stiffer springs and shocks and that makes it even worse.  Then add low-profile tires to the mix and it can really get bad.  My solution:  Avoid bumpy roads!  Also, I am installing some fiberglass rear leaf springs to reduce unsprung weight.  That weight is the main culprit.

Ah...I Shirley ain't no expert butt (TS&T) it seems to me that  the  weight of the springs (bolted to the  frame, as it  were)  is  "sprung weight".  The rearend, wheels, and tires and even a percnetage of the driveshaft weight, bouncing along to every lump in the road is  "UN-sprung weight"  which we do want to keep to a minimum.  Which is partly why indy-pendant suspension  is usually better.

Just thinkin' out loud.

Also:  MS call me regarding that list we put together for Arizona.  I spoke with the guy...almost wish I hadn't.

BB

Last edited by Bullet Bob (5/28/2013 5:43 PM)

Yeah... I have the same problem when I push too hard on the loud pedal...Some have told me to ease up on the pedal pressure... Can't seem to get that hang of that.

mark1965 wrote:

i have a 65 coupe 302 t5 when i drive the car on rough roads over dips bumps or potholes the rear and feels like it wants to fish tail a little i installed a new set of leaf springs new hardware and new rubber bushing. any ideas on what would causing it .

 
Yep, thats the way they drive. As someone indelicately put it on this Forum, "...those old Mustangs aren't sports cars...".  Much of what we do with our modifications is trying to push them into sportscar like territory.  That is why there is so much discussion of different suspensions on the Forum.  For something like $6000-10,000 you can have modern geometry four wheel independant suspension on your 47 year old car.

To get unsprung weight the typical way, you put your car on jack stands supporting on the frame/body. Remove spring and shock, unhook swaybars. With tire and wheel back on, support the tire on a scale at normal ride height. the scale reading plus 1/2 the shock and spring weight is you unsprung weight. this tells me that half the sping weight is assumed as unsprung. Also, if you run your shocks upside down, your unsprung is less by a little.