Ok, I rarely post, but read all the time. I just put a new composite rear spring, new shocks, new lower shock mounts, and a new adj strut rods and bracket on my 1968. It was time to redo the major componets of the rear susp.

See if you can diagnosis the issue now. Before the new suspension the car did not have a single vibration problem. Now when it is under a load it vibrates like hell. If the car is just going down the road in gear there and no load it DOES NOT Vibrate. If you gun it in 1st, 2nd, 3rd...when the torque comes on it shudders like hell. I gunned it and let it shudder and then pressed in the clutch and it stops.

It drove perfect before it took off the old spring (which was worn out) and the old struts and shocks (which were toast). Now with all new stuff it drives like crap.

Do you think the pinion angle can some how be out of line even though I did not move the pumkin? Can a new spring move the rear diff enough to through out the driveshaft alignment? I have read several post about driveline vibration, but they always seem to have pulled out the tranny or rear diff. I did not touch either.

Help!!!!!

 

Check out the U-Joints. I assume since the mods you made it is sitting higher, usually does. So start there and eliminate the possibilities. Unless its been fornicated in the past the pinion angle shouldn't be the problem. I would eliminate the moving parts first.

 

depending on your shock selection ,compsite springs usualy needs special valving shocks.. possible cause of vibration...

 

It is sitting much higher. The old spring was almost flat. What exactly do you mean when you say check the U-joints? What am I checking?From a visual perspective nothing seems wrong.

Thanks for any advise.

 

Drop the half shafts and inspect the pin bearings inside the U-Joints. If the car is sitting way high you might just need to change the spring bolts, Longer bolts will lower the *** end. If its sitting high it may have the half shaft angles way off causing the vibration.

 

Replace the leaf spring bolts with longer ones!

If your car is sitting pretty higher than before, the U-joints of the halfshafts may are binding!

Do it before to make some damage!

 

I think I would agree that the only difference is the height. I would also assume the angle of the half shafts are the culprit of the vibration.

I have inspected the halfshafts and there are no signs of binding. It would be very easy to detect considering they are freshly painted.

 

The bolts the spring came with hang all the way to the lip of the rim. The instructions say the have extra threads.

Does anyone else have any other suggestions.

 

I am in the process of finishing up my rear end and I did remove the diff. I'm getting worried now in case I have a problem, if you find the culprit please post and I will do the same!

 

I just put some 10 inch bolts in the springs. It is raining here, so my test drive was only about 1/4 to a 1/2 mile. I don't drive it in the rain. Anyway, I believe the additional drop of the rear has solved the problem. I did not feel the vibration when I put a load on the drive train.

When it clears up tomorrow I will give it a full test and will post any further issues, but I think it solved the problem. Thanks to everyone.

 

Post some pics of the *** end too, that will help us figger it out

 

It is confirmed. The car no longer has drivetrain vibration. It must have been the half shafts binding just ever so slightly. When the diff was under a load it pushed it over the edge and must have touched by the knuckles.

Thanks again and I hope this helps anyone in the future.