73 2wd 390 c6

Took my truck out today for the first real drive after a djm install and new wheels and tires. I've got an up and down bounce going on. I can feel it up to 40 mph. It gets noticeable at 35 to 40, but when driving slow I could see that it was still happening.

I've got all new shocks, tie rods appear good and tight, new u-bolts on the rear, new king pins, and everything appears tight and in the right place.

What else should I be checking?

 

Sounds like worn or cut springs. Kids cut springs all the time when they lower they're lawnmower cars. They will bounce like hell after that because the spring rate has been altered.

If you used actual lowering springs then that may bypass that issue. Only think I can think of at that point would be that the lowering springs are also softer than they should be.

If the front coil springs aren't it, then maybe you have some odd tire sidewall flex going on?

 

Could have an out of round tire! have seen it happen

 

Did you fully stroke the shocks up right to get the air out before installing them? Could have air trapped in them.
I would also call DJM to see what they have to say about it.
Dave ----

 

It occurred to me that when I drove the truck to get it aligned I didn't remember a bounce and I had it up to speed, so whatever happened must have been since then... and the tire shop/alignment shop had a hell of a time trying to figure out how to align the truck (4 hours of them actually working on it, never again Tire Kingdom). I thought maybe one of the wheels hadn't had it's lug nuts torqued down and when I jacked up the front to check for play... it sure was there, not from the lug nuts, but crown nut that holds the center link and inner tie rod. It is completely loose with only the cotter pin holding in on.

That has to be it. Unbelievable. I hadn't checked that since reassembling everything because I never touched it and it was secure when I did my final check over of everything. They must have forgotten to tighten everything back up when they did the alignment!

It's too late here tonight, but I'll get it all tightened back down tomorrow and check around at that they didn't leave anything else half done.

In regards to the responses above, thanks. The springs are all still stock front and back and I did let the shocks compress and decompress several times before installing. The truck seems fine on all four corners when I tried bouncing it up and down by hand. We'll see.