Rear end vibration

[500stroker]

I have a 66 Satellite that I am trying to chase down a rear of the car vibration The car has a 8 3/4 posi and has been mini tubed and connected with Cal-Trac bars. 500 cid with a 727 auto
The vibration comes on at about 2000 rpm under acceleration, no vibration of the pedal or coasting in neutral.
I have run down the the following to date;
Balanced and checked for straightness rear tires and rims
Replace the entire drive shaft, trans yoke and u-joints
Replaced both rear springs with all new poly bushings
No change
Before I tear in the rearend does anyone have any suggestions.
Thanks in advance

 

[OldRunner]

Interesting, I have the same issues on my 67 Coronet, the only thing I see similar are CalTracs ???? If you get it figured out, let me know, I will do the same.

 

[daredevil]

A broke or loose trans mount can cause this

 

[5.7 hemi]

X2, good call DD.

 

[BIGSHCLUNK]

Been there myself DD. Check your mount!

 

[1moreproject]

Have you checked the pinion angle?

 

[500stroker]

Pinon angle is correct at -3 degrees
What I am not sure of is the drive end of the 727 currently at -1 degree
I will check trans mount.
Thanks

 

[RustyRatRod]

Who said -3* is correct? Just wondering.

 

[moparstuart]

could be the pinion bearing where the yoke it , my dana did that

 

[Bad Sport]

-3* in relation too................?

 

[500stroker]

I built a 1965 Pro street Vette in which I installed an 4 link rear suspension from S&W
The manual it came with stated to set the pinion angle at -2 to -4 degrees in relationship to the center line of the pinion shaft. In other words, the pinion yoke should tip very slightly towards the ground. I confirmed this with a local chassis builder.
I put over 20,000 hard miles on that Vette and never had problem with the driveline.
Than I got Mopar fever I'll never go back.

 

[Supershafts]

That's not right, the angle is relative to the shaft, what you want to happen is when underload you want 0.0 between the shaft and pin.

Race cars are supposed to have no angles and when you have a 4 link you can usually set it at 2 down from 0.0 as the link may have 2 degrees upward rotation, 4 degrees would be to much.

A leaf spring suspension may need 5 degrees diff of the shaft or 4 degrees that is all dependent on your suspension and how much it allows the pin to rotate.

You need more detail in your situation as there will be no way for anyone to help you with it starts at 2k under accel ... really it does this only at 2k under load in 1st, 2nd and 3rd.... YOU NEED LOTS OF DETAIL......
I specialize in driveline and you will not get any correct info with that description, and i can't drive your car from here.


You need to explain like this, starting off from a dead stop it immediately starts a vibe at 2000 rpm (and i have ___ gear ratio with a ___ trans and it has a ___ TC) it continues with the vibe thru 1st, 2nd and 3rd gear until i let off the gas, or it continues till the load is no longer on the driveline and is smooth at ___ and there are no further issues at any other speed...


Anything less than that you'll get wild insane answers from people here and you will get guesses from them and you'll spend your money on those guesses.

.

 

[RustyRatRod]

I built a 1965 Pro street Vette......

Well nuff said then. Set it up like a vette.

 

[Dobaroy]

Good Luck 500 Stroker, don't have any suggestions for you but hope you find the vibration.

 

[500stroker]

That's not right, the angle is relative to the shaft, what you want to happen is when underload you want 0.0 between the shaft and pin.

Race cars are supposed to have no angles and when you have a 4 link you can usually set it at 2 down from 0.0 as the link may have 2 degrees upward rotation, 4 degrees would be to much.

A leaf spring suspension may need 5 degrees diff of the shaft or 4 degrees that is all dependent on your suspension and how much it allows the pin to rotate.

You need more detail in your situation as there will be no way for anyone to help you with it starts at 2k under accel ... really it does this only at 2k under load in 1st, 2nd and 3rd.... YOU NEED LOTS OF DETAIL......
I specialize in driveline and you will not get any correct info with that description, and i can't drive your car from here.


You need to explain like this, starting off from a dead stop it immediately starts a vibe at 2000 rpm (and i have ___ gear ratio with a ___ trans and it has a ___ TC) it continues with the vibe thru 1st, 2nd and 3rd gear until i let off the gas, or it continues till the load is no longer on the driveline and is smooth at ___ and there are no further issues at any other speed...


Anything less than that you'll get wild insane answers from people here and you will get guesses from them and you'll spend your money on those guesses.

.

Hay, looks like I found someone that can help.
Please dont jump my *** I am new at this, cant type worth a dam and by no means am I a Chassis Engineer. I believe you to be correct that every drive line type and certain manufactures may differ on how/what diff angle to run, street or strip etc.
Start over, I have a 727 w/2500 rpm stall. 83/4 with a 3.23 gear ratio
The vibration is only noticeable in 3rd gear, highway speeds
Vibration starts @ about 2200 rpm and gets worst as you go up in rpm
It only vibrates under load, if you back of the gas pedal, feather the pedal or put the trans in neutral the vibration total disappears.
No vibration in 1st or 2nd gears
It's very difficult to describe W/O driving it
The car is currently at a remote shop having exhaust work completed so I have not been able to check the trans mount.
Thanks again

 

[Supershafts]

If the vibe goes away in neutral and you feather the pedal then you might want to look at the exhaust.
Don't rule it out as i have fixed many a supposed driveline vibe by finding a badly put together exhaust or simply finding a hanger worked better in a slightly different location.

Though i need to know exactly how far the vibe carries on for, at 2200 in 3rd gear is exactly when it starts ? the very slightest vibe is only present at 2200 ? how violent does the vibe get ? and exactly how much further can you go in speed before it changes or gets better ?

So saying at 4500 is the vibe so bad it's shaking everything or is it less than at 2200 or 2600 or is it gone totally.

When you go to neutral a few things are changing, the motors load on the driveline, the front half of the trans is slower then the output and driveshaft, the exhaust pulses, and load on pin so when you drop it into neutral and the vibe disappears and the only thing that has changed at that moment are those listed, and yes the issues with the pulsing can be different when you're in 1st and 2nd as so is the load on the motor.
It could also be a TC issue
And you are right, it is very very hard to pin point the vibe sitting here

 

[500stroker]

I will have to drive the car to collect more data.
I am meeting up with my exhaust guy this week and we will look over the hangers.
I will let you know what I find.

 

[500stroker]

If the vibe goes away in neutral and you feather the pedal then you might want to look at the exhaust.
Don't rule it out as i have fixed many a supposed driveline vibe by finding a badly put together exhaust or simply finding a hanger worked better in a slightly different location.

Though i need to know exactly how far the vibe carries on for, at 2200 in 3rd gear is exactly when it starts ? the very slightest vibe is only present at 2200 ? how violent does the vibe get ? and exactly how much further can you go in speed before it changes or gets better ?

So saying at 4500 is the vibe so bad it's shaking everything or is it less than at 2200 or 2600 or is it gone totally.

When you go to neutral a few things are changing, the motors load on the driveline, the front half of the trans is slower then the output and driveshaft, the exhaust pulses, and load on pin so when you drop it into neutral and the vibe disappears and the only thing that has changed at that moment are those listed, and yes the issues with the pulsing can be different when you're in 1st and 2nd as so is the load on the motor.
It could also be a TC issue
And you are right, it is very very hard to pin point the vibe sitting here

I got the car back after exhaust work was completed and the vibration still is there. Just to prove out the exhaust we change all the hangers to a different with more flex and it made no difference, so it not the exhaust causing the vibration.
Again,
The vibe starts at 2200 rpm and settles out at 2600 rpm but never really goes away above 2600.
It never shakes the car violently but is more like an hard rumble that comes in very quickly at 2200 never gets worse and will almost go away after 2600 rpm.
Vibe is the same in all gears and does not vibe in neutral coasting or parked
Vibe is the worst under any acceleration and will almost disappear off the gas pedal.
You feel the vibration in the seat of your pants and in the floor, not in the wheel or pedals.
Trans mount is stock rubber and appears to be OK
Motor mounts are solid aftermarket
I ordered a new trans mount, see if it makes any change
Any thoughts? I am lost:confused5:

 

[Big Sugar]

Do you feel it out back ? or is it all over the car ? Could be a flex plate or bad torque converter.
You said you had your driveshaft checked, was it out of balance ? when you reinstalled it did the vibration change at all ?

Bent axle maybe ?

Ron

 

[500stroker]

Do you feel it out back ? or is it all over the car ? Could be a flex plate or bad torque converter.
You said you had your driveshaft checked, was it out of balance ? when you reinstalled it did the vibration change at all ?

Bent axle maybe ?

Ron

The first thing I did to try to resolve this was to put in complete new driveshaft, new tube, new u-joints, new yokes and balanced.
Vibrates from the front fenders back.
I spoke with a custom trans and T/C guy today and he stated that if there were something wrong with the T/C or the flex plate that it would vibrate in or out of gear, anytime the engine were at 2200-2600 rpm.
With the car up in the air the wheels and tires run pretty true.
Can brake drums be out of balance?