vibration problems

[71dustrunner]

Hi I have restored a 1971 Road Runner 440+6 with a 4speed trans. I am not a super mechanic but it's fun to preserve those muscel cars and I do the best that I can. Now to my problem I have some heavy vibration in the car and some noice from rear end. The only thing that I have done with the rear end is that I have put some lowering block , could that be the problem? Have also but a new flywheel and clutch. I am hoping that someone could help me with some advice. The season is just around the bend so I want to take the bird out. Regards Anders From Sweden :help:

[pigman]

Hi I have restored a 1971 Road Runner 440+6 with a 4speed trans. I am not a super mechanic but it's fun to preserve those muscel cars and I do the best that I can. Now to my problem I have some heavy vibration in the car and some noice from rear end. The only thing that I have done with the rear end is that I have put some lowering block , could that be the problem? Have also but a new flywheel and clutch. I am hoping that someone could help me with some advice. The season is just around the bend so I want to take the bird out. Regards Anders From Sweden

Wow ... many problems could cause this. I had the same problem after my rebuild. In my case, I found that my bell housing had a crack in it and was actually moving back and forth under accelleration. I think another typical cause of vibration is a drive shaft that is not balanced. I fixed all that stuff and found that my original 500 wheels from 1972 were just not perfectly round any more. I changed em out for a set of Craiger SS and my ride is now smooth!

http://www.tpigman.com/plymouth/crusin/33.JPG

[landon1]

Maybe a motor mount? I have one that's needing replaced and that's made mine a little bit rough.

[pigman]

Maybe a motor mount? I have one that's needing replaced and that's made mine a little bit rough.

YUP ... I forgot that ... I had 2 broken motor mounts and that problem kept coming up .. till I got one of these:

http://shop.store.yahoo.com/chucker54/bentost.html

WORKS GREAT ... looks better than a chain.

[road chicken]

Anders,

Ok lets see ifwe can get you sorted out.

First thing- Is the vibration engine specific?

Or is it show up at a certain rpm/gear/ KPH - or a combonation.

It is possible that the lowering blocks did cause this. But not typical. On these blocks- get rid of them. By putting space between the axle and the spring, the axle gets more leverage against the spring seat. That is not where you want to add stress.

You can accomplish a 2 in ( 50mm) drop inthe rear suspension just by reversing the front spring mount. It will take a little bit of filing as the hole pattern is designed not to let assembly line workers do this. It is a much better way to accomplish that.

Now , Of the guys I know that have dropped the rear like this- none of them have issues with vibration. So that shouldn't be it.

Since you have just restored it, I'll list a few of the basics.

If the engine was an original 440-6 - does it have the specific balancer onthe crank.

Did the same shims that were between the transmission and its rear mount get replaced? These get left out alot on rebuilds but are critical. The angle between the centerline of the transmission and the angle of the driveshaft should be 0-5 degrees, 2.5 optimal. The drive shaft should angle down to the rear.

The Driveshaft to pinion angle. The pinion should point nose down about 2 degrees at rest. If it is not, you will need to buy wedges to get the proper angle.

Get the pinion angle set first, then you can shim the tranny to where you need it.

Is the driveshaft balanced?

Wheels and tires?

Mounts and bolts all tight?

Post back and let me know under what circumstances it vibrates.

We'll see if we can get this smoothed out.