Was this before or after all the other drivetrain work? Just trying to establish a time line of what you did and the effects of what you did.

Using wheel chocks or If handbrake works well enough to hold car well, engage it tightly and with transmission in low gear, give it some gas and let out the clutch. Have an assistant view rear springs while doing so. Any shudder or other observations of note in behavior of springs or driveline?

Would certainly be better to be on a drive on lift,,,,,looking for unusual engine and transmission lift or rock.

Reposting this as it may have slipped by,



This can easily be done by adjusting the length of the clutch rod.

Yep this setup Wayne suggested. It just happens to be the same setup I used in my stock 383 4 speed Super Bee a few years ago. Same use, just street. Not one issue with that.

Adding the super stock springs is the last thing I did. I then stuck the traction bars on.

When I was going over the linkage looking for irregularities, I did adjust around on the rod just to see what would happen at various engagement points. It shook at all of them.

I need to do this test again. I've done it once and I'm pretty sure I saw no shake with that. That's what pointed me to the back end and changing the springs.

Could clutch disc when released, not move freely on transmission main spline. I had always checked for this many years ago when was still replacing clutches, did so before bolting pressure plate in place. More than once had found a problem,,,,and a couple of times with a disc not runing true when spun on a smooth bench top surface.

I will post this thought on the other thread of the day suggesting another clutch problem.

Just did another check of my LH motor mount. This car has power steering so it's not the easiest to see but I set the mercy brake on the car and popped the clutch a few times. Had someone watch the motor mount and even took a video. The rubber does separate and is cracked almost all the way across about 1/16th from the top of the mount. It's not all the way thru though cause the motor still does not raise up enough from left to right under torque for the air cleaner to tag the hood. It does indicate a questionable mount. Car does not shake or anything slip while the brake is set and popping the clutch to raise the motor.

Did you check/reset the pinion angle when you put those springs in?

The fact that you said it went away , for the most part , with snubber bars up against the rear springs tells me it's a driveline issue. Pinion angle is the first thing to look at.

Where's Quicktree ?

Yes I did experiment with the angle shims after putting the new springs in. I've looked at this pinion angle allot and tried different negative angles with no success in getting rid of the shake.

Another odd thing to me is that when I set the mercy brake and bump engage the clutch, I get no shake. That test led me to the rear thinking the motor, tranny clutch area was fine.

How about an actual pinion angle reading ? Was negative actually the correct way to go ?

Yes. Negative is where you want to be in relation to the tranny tail. My readings have been anywhere from -2.5 to -8, depending on what shims I had in place.

I see in the latest edition of Hemming's Muscle Machines there is a fella with a 69 Dart 383 4 speed car & 3.23 SG with the same problem that wrote in. His car is original also with the drive train rebuilt. Common theme it appears. He has also replaced the clutch twice. New flywheel and various parts as well.

I have a 69 383 4 speed dart with the original sagging rear springs , I don't remember any issue with either a borg&beck 3 finger or the McLoed Borg&Beck/Long. The stock borg&beck did have a vibration issue in the engine itself but that was caused by the flywheel that was cut at an angle and was hot fully neutral because of it.

Where is Rhinodart in this discussion? No disrespect to anyone who has posted but if anyone knows about this kind of generic problem he should.

I think Rhinodart lives in Illinois as well, not too far from me. Heck I would take the car to him if he didn't mind looking at it for me. I've tried so many things to this point that I'm wondering if it's something I've missed along the way. I've had lots of other eyes on this thing too but I wouldn't call the eyes real experienced on 4 speeds and their setup. I believe that's what this will take.

We are all curious on this one, hopefully if cause is found that finding is posted.

All too often this important close out report does not happpen. Important for those who have posted their ideas,,,and for the next member to experience the same problem.

Absolutely. Responding back with a post will be the first thing I do after figuring this issue out. 40 years of working on these things, mine and my friends cars, and I've never have had a problem I've worked on for so long.

I do plan to replace that motor mount but since it's not cracked all the way thru I don't believe it is the source of the shake.