Need a little help from you guys....trying to get my 85 running after a two year(yep, two year) rebuild from the ground up, but I've got this terrible hammering sound from the rear suspension. I had a half-shaft u-joint break, and I just finished putting on new wheel bearings, u-joints, and putting the rear suspension back together. But when I try and drive it, I get this horrible metallic hammering sound, like something is coming apart. I have previously done the drive shaft u-joints, as well as a newer gearing in the rear end. The rear end has 3:31 gears, and has about 50 miles on it.
Every thing else is brand new...I put the car up on jack stands, and checked the play in the wheels...at 12 and six it's tight as a drum...no play, and at 3 and nine, the same....tight and no play. Tried to turn the half-shafts in Park, and no go...both sides tight. Put it in drive, and turned the wheels by had, and no noise at all. So I start it up, put in Drive, and rev the engine, hoping to find the culprit, but it's quiet as a mouse!!??. Take it off the jack stands, back it out, and all's good, drop it in drive, and start to ease down the street, and BANG!BANG!BANG! WTF!! Help me out here guys, what could this be?? only happens when the car is on the ground, and only when it's moving forward.....don't want to drive it, for fear of tearing something up, but I don't have a clue

Cheers,
Michael

 

sounds like a driveline part is hitting the exhaust somewhere check the halfshafts in the normal plane of rotation without jacking it. take off the spare tire and cover, and crawl under it in the middle, lay on a creeper, and have your better half slowly go forward with u under it. dangerous if you fight with your wife.

 

I would need to hear it. Can you try and record it somehow? Does it go exactly with each wheel revolution?

Sounds like something is hitting only when the suspension is compressed.

Are all the ujoint strap bolts tight? Are the T-50 wheel bearing flange bolts tight?

Whatever is hitting, you should be able to find some shiny spots now. Start taking it back apart.

 

A broken gear in the transmission can also make that sound, I know because I've done it.

Sounds literally like someone hitting the side of your head with a nail gun.