Vibration 45-50

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jpl572103

jpl572103

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66 Dart, 833od. I have a 3rd/4th gear vibration while cruising, more vibration in 4th depending on how much I push the gas pedal. It's not a revolving type vibration, its just there if that makes any sense.

Has a new balanced 3inch steel driveshaft, has a shortened 8 3/4 with super quiet 3.55 sure grip gears,has diff additive, has dr diff axles. The Vibration happens when I hit 40-45 in 3rd or 4th, worse in 4th, but when I put in Neutral it seems to diminish or go away mostly but when giving throttle it comes back and when cruising it will stay there. Would the shortened 8 3/4 be causing this say if the pinion angle were wrong? I don't think the drive shaft is the issue since the car is smooth under 40 and vibration almost goes away when in N. Also have new Jegs wheels/tires/ balanced.
 
The shortening of the rear housing would not matter. If the pinion angle / transmission angles are off it could/would. If the U joints are not tight in the caps. Could be motor / trans mounts. Could be wheel bearing, who knows….

More info is necessary. Like where the vibration is in the car. What’s it feel like, front to back, side to side, up and down.
 
jpl572103 said:
66 Dart, 833od. I have a 3rd/4th gear vibration while cruising, more vibration in 4th depending on how much I push the gas pedal. It's not a revolving type vibration, its just there if that makes any sense.

Has a new balanced 3inch steel driveshaft, has a shortened 8 3/4 with super quiet 3.55 sure grip gears,has diff additive, has dr diff axles. The Vibration happens when I hit 40-45 in 3rd or 4th, worse in 4th, but when I put in Neutral it seems to diminish or go away mostly but when giving throttle it comes back and when cruising it will stay there. Would the shortened 8 3/4 be causing this say if the pinion angle were wrong? I don't think the drive shaft is the issue since the car is smooth under 40 and vibration almost goes away when in N. Also have new Jegs wheels/tires/ balanced.
Click to expand...

When I start looking for a vibration the first thing I do is put the rear on stands and duplicate the speed.
If it’s still there I pull the tires and test again.
Then put the front tires on the back and test again.
This mostly eliminates tires as the problem.

This assumes the vibration is not there in neutral at the same rpms.
If it is, then its not the drivetrain but somewhere between the front balancer and trans.

The part that sucks is you can’t trust anything anyone has done.
I had a driveshaft balanced to the tune of $125 before and still it was out of balance.
Also had tires balanced before that ended up being an ounce out of balance.

Unfortunately we can’t trust anything someone else does anymore.
 
All good advice. Especially if you don't do it yourself, you don't really know what you have. I get that. The vibration comes on in 4th at 40+ mph, it's in the seat, steering wheel, etc. It's like a switch is flipped and the whole car vibrates. I just don't know why it goes away when putting in Neutral. I'm thinking the transmission is the cause only because it whines in ODrive.
 
So just got back from a drive/ Car has not been started until now. When cold there is no vibration, after engine reaches op temp and after shifting up and down a number of times, the vibration starts to show itself. I think it's in the 833. As soon as I put in N, vibration gone. Not sure what is spinning or stops spinning in the transmission. I have been searching for a unit that is in working condition to swap with this one. Haven't found yet. Passon has units for sale. Brewers does not.
 
jpl572103 said:
So just got back from a drive/ Car has not been started until now. When cold there is no vibration, after engine reaches op temp and after shifting up and down a number of times, the vibration starts to show itself. I think it's in the 833. As soon as I put in N, vibration gone. Not sure what is spinning or stops spinning in the transmission. I have been searching for a unit that is in working condition to swap with this one. Haven't found yet. Passon has units for sale. Brewers does not.
Click to expand...

Is rebuilding out of the question? These are very simple. The rebuild kits are also reasonable..
 
jpl572103 said:
I plan on rebuilding. Wanting a 2nd unit that is working to install, then rebuild this one.
Click to expand...

It’s super rare that a trans causes vibration.
You can test that by simply pushing the clutch in.

If I was driving your car I could tell you exactly where the vibration is coming from, as I made a living diagnosing and fixing such problems for a large shop.

Diagnosing via description over text is almost impossible.

Driveshaft angle, there is a app to test that.

Trans in gear and clutch in while engine is at rpm.
Does the vibration go away?
If not it isn’t the trans.

But could be engine driveshaft or wheels and/or tires because they are all still spinning.

Vibration parked in neutral and clutch out with engine rev is engine or clutch assembly.

Parked in neutral with clutch pressed and rev is pretty much only engine balance or engine miss fire.

Vibration accelerating only and not decelerating, is usually driveshaft Ujoints or pinion related.
Same for decelerating only.

Vibration in the steering wheel, usually tires ot wheel related.

There is a diagnostic for most every possible symptom.
It’s a matter of knowing what it’s trying to tell you when, and under what conditions.
 
So after more testing here is what I found. The vibrating issue is not really noticable until after a few miles of driving. Then it just creeps up while drving 45-50mph. I thought the vibration was gone when putting in N, but this time I got the car to 55 with the vibrating happening. Put in neutral and turned engine off. Vibration didn’t change. I think I’m going to get the tires checked for balance to start with. The good news is that it's a great grocery getter/around town car in the 25-40mph range.

IMG_3978.jpeg


IMG_3977.jpeg
 
jpl572103 said:
So after more testing here is what I found. The vibrating issue is not really noticable until after a few miles of driving. Then it just creeps up while drving 45-50mph. I thought the vibration was gone when putting in N, but this time I got the car to 55 with the vibrating happening. Put in neutral and turned engine off. Vibration didn’t change. I think I’m going to get the tires checked for balance to start with. The good news is that it's a great grocery getter/around town car in the 25-40mph range.

View attachment 1716265185

View attachment 1716265186
Click to expand...

Yep, tires, driveshaft, ujoint or loose yoke on the differential.
Tires is easiest to start.
Dont forget you can put it on stands to check things.
Spin the tires in the air at speed.
If you don’t find it put the fronts on the back and test again.

That is how I go about things, but obviously you can take it and get it checked if you like that better.
Done that before.

But you are learning diagnostics in the process either way.
 
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