Vibrations...

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Moparbaker

Moparbaker

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I've made sure the pinion angle is right, got new u-joint & felt with my hands the rear axel shaft ends on both side + incoming/pinion after a drive & all 3 are cold & bought new tires but there's still vibrations! I took engine & gearbox out from our old van & there was absolutely no vibrations when it was still in the van.
(Engine is a 318 & gearbox is A500/904 with overdrive.)
So doeas anyone have any idea of what it can be..?
 
Moparbaker said:
I've made sure the pinion angle is right, got new u-joint & felt with my hands the rear axel shaft ends on both side + incoming/pinion after a drive & all 3 are cold & bought new tires but there's still vibrations! I took engine & gearbox out from our old van & there was absolutely no vibrations when it was still in the van.
(Engine is a 318 & gearbox is A500/904 with overdrive.)
So doeas anyone have any idea of what it can be..?
Click to expand...
Perhaps the pinion angle is wrong at the tail shaft. Wheels balanced?
 
A couple of suggestions come to mind:
I'm assuming you had a new driveshaft made for the A500 conversion, might be worth having the balance re-checked.
Ideal pinion angle is generally in the 3-5* down range as measured from the tailshaft, not from the horizontal (unless tailshaft is horizontal...). So, if your trans. tailshaft is installed at 3* down, you need to set your pinion angle 3* down from there, for a total of 6* down. All measurements are taken at rest, car's weight on the suspension.
You might also want to double-check your pinion nut- they have been known to loosen up and can wreak all kinds of havoc- you may not notice it with a casual inspection. It's a bear, but make sure it's torqued to factory spec. Use a new nut if you find it to be loose.
 
I'd start with checking the driveshaft runout. Easy to do if the car is up in the air. Fire it up, put the car in gear, and let the driveshaft turn while the engine just idles. If you see any wobbble at all, you need to redo the driveshaft. You can also check if the vibration changes by raising and lowering the rear axle while running the car in drive at the point (RPM/MPH) where you have been getting the most vibration. If it's a pinion angle problem, you should be able to find an angle where the vibration stops. Just make sure the car is secure on the lift or jack stands, someone sitting in the driver's seat in case of emergency, and nothing under the vehicle......including you!
 
What rearend? Some pinions you can tighthen with no issues because it is shimmed, but if it has a crush collar you can reak havoc.
 
Shaft is ballanced, tires are ballanced, shimed the pinion angle by the leafsprings & so on... The vibrations are more or less in all speeds. Rear end is a 8.1/4.
Gonna try to run it ilding lifted up & look then... Thanx!
I'll be back telling how it went, tomorrow.
 
So if you shift into neutral at road speed, does the vibration go away or stay the same? From your description, it sounds like the vibration would continue the same, but I want to be sure to understand.
 
Moparbaker said:
I've made sure the pinion angle is right, got new u-joint & felt with my hands the rear axel shaft ends on both side + incoming/pinion after a drive & all 3 are cold & bought new tires but there's still vibrations! I took engine & gearbox out from our old van & there was absolutely no vibrations when it was still in the van.
(Engine is a 318 & gearbox is A500/904 with overdrive.)
So doeas anyone have any idea of what it can be..?
Click to expand...
So...A500 conversion with the upper crossmember fab reduction and the lower crossmember retrofit or US Cartool member? Has the floor been modified for clearance if needed? Assuming it’s an “A” body.
Are clearances sufficient to ensure no transmission contact?
New rubber transmission mount?
As the motor and tranny rotates under load it could make contact causing vibration.
Any contact with the tranny to chassis at all will result in vibration along with the usual suspects.
Pics might be a big help too.
 
It's a rolling thing; starts at about 30 m/h when cold & then it's on even if I've stopped & shut it off for a while. When standing still there's nothing even when reving & if I put in neutral while driving & just roll it continues. I wonder if it could be the gearbox..? It also changes gear quite late. Could it be that the converter has to be bolted on in a certain way if it's been ballanced from factory?
 
Ok, so same engine tranny that you pulled because in my dumber years I bolted an auto to a previous 4-speed car and had the same symptoms until the correct dowl pins were put in place on the back of engine. Swore it was the rearend. Put a complete overhaul kit in it with same results .
 
if you feel it in the seat while driving i would look at the pinion angle,u joints,drive shaft.i had a drive shaft balanced 2 times and was told it was good.bought a new ds from strange engineering and the vibes went away
 
Moparbaker said:
It's a rolling thing; starts at about 30 m/h when cold & then it's on even if I've stopped & shut it off for a while. When standing still there's nothing even when reving & if I put in neutral while driving & just roll it continues. I wonder if it could be the gearbox..? It also changes gear quite late. Could it be that the converter has to be bolted on in a certain way if it's been ballanced from factory?
Click to expand...
OK, from the above, it is clearly somewhere from the tailshaft and output shaft of the trannie and on back to the rear end. No vibration when sitting still and revving rules out the engine and TC as suspects.

One more thing to check (I am not sure you have done this yet.): Jack up the rear axle with the wheels off but some bolts to secure the drums to the axles; run car in gear to get the axles rotating and use a reference to see if the drums/axles are wobbling around and around. That would indicate a bent axle.

As for the u-joint angles, know that you need to try to get the u-joint angles at the pinion AND up front within a degree of each other. It is not clear that this has been done.

And a crazy thing to try if nothing else works: Attach a 2 kg weight to the tailshaft of the transmission.
 
Yep, the engine & gearbox are "siblings" from the factory.

Wouldn't I notice bearing problems if a shaft would be bent? As I already wrote I've felt the shaft out by the ends after I've been driving & they're cold. Gonna do that trick anyway.

I've alreday shimed the pinion angle before buying new tires, so that's also done.

The thing is also that I've been driving the car like this for about 7 years now exept for the engine that I installed 3 years ago, but it's still the engine & gearbox that came together from the factory. & it was last summer I noticed the vibrations & since then I've not driven this car much cuz life's full of other stuff too so it's been sitting a lot I've rebuilt exhaust system & tinkerd with small stuff, only driven to get groceries & such.
 
Try unbolting the driveshaft & turning it 180* at the rear axle. Check to see if the vibration is still there, If it's better, or worse &/or still there it's time to have the shaft balanced.
 
Run it on idle while on stands & sure enough... something has happend, the shaft was kinda jumpy. Turned the shaft & the same!
Now it all goes down to be bench checked.
 
Moparbaker said:
I've alreday shimed the pinion angle before buying new tires, so that's also done.
Click to expand...
Yes, we know you have shimmed the pinion angle. But that is not what has been asked twice now: Have you made sure that the 2 u-joint angles are within 1 degree of each other? That is more than just setting the 1 angle at the pinion.
 
I know of people who hit road debris to have it flip up and hit the driveline... a small dent can cause issues .
 
Yep, one more thought that have enterd my mind, gravel roads aint always smoooth. (& I aint living in a city anymore cuz I've had enough of stressy trafic.)
 
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