67 - Rear coil spring question

[oldman3]

I redid a friends 67 pickup a couple years ago. We installed a drop kit from CPP. We did a 5" coil spring drop in the rear, with relocators for shocks, c-notch, etc. The pickup is a 67 longbed stepside. It was orginally a 1/2 ton heavy duty long bed. We kept the long bed and added a gas tank at rear of frame. What is happening now is when you ran down the freeway at about 70 mph, the rear axle bounces like a rubber ball. It's not real bad, but you can see it if you watch from another vehicle. I'v talked with CPP and they think I should go to the 4" heavy duty drop coil spring. I think this may take care of the problem, but wanted to check with people on here who may have had this problem, or can help out, before we order the new springs. I have attached several pics, showing old springs & new, and the current underside of pickup. Let me know what you think.

Pic 1 old and new springs
Pic 2-5 shots of undercarriage

[fastwillie 696969]

do you know the spring rating ?

[oldman3]

Pic 1 more undercarriage.

Pic 2 How tire looks in the opening, tire is a 255/60/17 on Coy rims

Pic 3 & 4 Before and after shot.

[oldman3]

Originally Posted by fastwillie 696969

do you know the spring rating ?

No I'm sorry I don't, they are what CPP sold, part # was 603-5.

[Richard H.]

My first thought would be gas adjust shocks or coil overs. Thats some slick detail right there...very nice.

[oldman3]

Originally Posted by Richard H.

My first thought would be gas adjust shocks or coil overs. Thats some slick detail right there...very nice.

I had thought about coil overs also, but cost is the problem. Thanks for the kind words, appreicate it.

[Jessechop]

Just a stupid thought, but are the shocks just plain old worn out?

[DesertCat]

Sounds to me like there isn't enough dampening with the shocks, maybe they are too weak or worn out. Has this always happened?

Out of balance or out of round tires could be a cause... I chased a problem like this once and after checking everything (and I mean everything) 2-3 times, replaced the 6 month old tires... solved. So just because they look nice and new doesn't necessarily mean they aren't a problem.

Your mileage may vary...

[oldman3]

Originally Posted by Jessechop

Just a stupid thought, but are the shocks just plain old worn out?

Shocks are brand new Doetsch, with less that 1500 miles.

[oldman3]

Originally Posted by DesertCat

Sounds to me like there isn't enough dampening with the shocks, maybe they are too weak or worn out. Has this always happened?

Out of balance or out of round tires could be a cause... I chased a problem like this once and after checking everything (and I mean everything) 2-3 times, replaced the 6 month old tires... solved. So just because they look nice and new doesn't necessarily mean they aren't a problem.

Your mileage may vary...

My thoughts with the dampening also, just not sure, they are new and a brand name (doetsch). I though if the springs were not stiff enough, that the shocks couldn't control the bounce, don't know. Never thought about the tires, will have to talk this over with the owner. Thanks, Jim