Driveline vibration

[garagedoordennis]

In a quest to make our vans the best they can be I'm always improving on things . My next task is to try and smooth out my driveline. It's nice till 60mph ...then it has a slight ossilating vibration. Stays there till 75 then seems gone again. Things I've noticed
deceleration...still there
Acceleration...still there
Don't feel it in the steering wheel
Tire balance seems spot on
My drive line is a 350/200r4 with the engine lowered 2" with
a block. Motor mounts are urathane

[panelmanrd]

I would take a look at the pinion angle, needs to match angle of engine output shaft.

[xjamesx]

I second that. I have been chasing a slight driveline vibration since I swapped the full drivetrain last year. Adjusting the pinion angle helped a decent amount, but I think my last little bit of vibration comes from my driveshaft. I’ll get that out and balanced this winter.

[garagedoordennis]

is this corrected with shims then ?

[panelmanrd]

when i lowered things, i used the trans mount to adjust the angle to match the rear axle

[xjamesx]

is this corrected with shims then ?

yeah, I bought some shims from speedway motors or Jeggs, I think.

[BILLJ386]

I Don't want to sound like captain obvious but....

In a quest to make our vans the best they can be I'm always improving on things . My next task is to try and smooth out my driveline. It's nice till 60mph ...then it has a slight ossilating vibration. Stays there till 75 then seems gone again. Things I've noticed
deceleration...still there
Acceleration...still there
Don't feel it in the steering wheel
Tire balance seems spot on
My drive line is a 350/200r4 with the engine lowered 2" with
a block. Motor mounts are urathane

A couple things that have worked for me are..
1) Does it have a grease fitting? if so fill it up. If not get one that does.
it will make a difference.
2) take the drive shaft loose and turn it 1/2 of a turn and put it back on.
better, worse or no difference?
3) If your wheel/tires are close to the same size swap front to back.
Don't do more than one time and see if the frequency (vibration) changed.
One last thing that I've seen done out of desperation that actually worked was to
Find someone you trust with your life.
Locate the biggest parking lot available.
set the vehicle up on 4 jack stands to ride height. Maybe 2' off ground.
Set the jack stands under the rear axle next to the springs and under the lower control arms up front.
Start her up Put in drive and bring up to the vibrating frequency.
Now raise the back up with a jack and/or lower with weights until the vibration either goes away. Gets worse. or it vibrates off the jack stands and launches....
Good luck!

[Vanner68]

If you dropped the motor 2" and didn't drop the trans 2", the tailshaft angle and pinion angle no longer match. Either drop the trans mount 2" or adjust the rear pinion angle with shims.

[garagedoordennis]

thanks for the ideas... I have brought the trans down, just made a new crossmember for it at the speed shop last week. The one that Taz and I installed really did that anyway I was just trying to make a better one. Tires are not the same front to back so that wont work but thinking that through when I had the other set of wheels and tires on it was still there. The driveshaft has come to mind as I did have it remade ( by a very good shop ) so there is a possibility. Im going to look a bit closer at my angles using a inclinometer to really see where Im at. I also bought a new trans mount so as RD said gives me another area of adjustment

[Leroy Jackson]

Another solution would be to run a double cardan u-joint or a Cv style joint off the transmission end and set the pinion angle for zero on the axle end. Not the cheapest, but if your setup has funky angles, this will work quite well. If you ditch the slip yoke setup as well, it will be smoother overall through out it's entire range of motion.

I run this type of setup on all my off road rigs.

[garagedoordennis]

I watch a video on you tube that showed the reason for the angle being the same. I bought a angle finder and my trans is (3degrees) and my pinion is (6degrees). I guess I alway thought from 4x4 days that you were trying to tip the axle toward the driveshaft but not in this case. I ordered some shims for the trans and a shim kit for the rear axle. Will try this out tomorrow and let you know how I come out

[garagedoordennis]

So i added three shims under the trans mount...this was a simple thing to do..I also did pull the drive shaft and rotate it 180. Test drove and was better...so i believe the goal is to achieve the smallest degree? So maybe i should put in the axle shims and pull out the trans mount ones?

[Vanner68]

So i added three shims under the trans mount...this was a simple thing to do..I also did pull the drive shaft and rotate it 180. Test drove and was better...so i believe the goal is to achieve the smallest degree? So maybe i should put in the axle shims and pull out the trans mount ones?

As long as the trans and pinion angles match, you'll be good

[CREWCHIEF]

Be sure that the pinion is nosed down and the crankshaft is sloped down from rear to front, or you will get a jump rope effect! Measure from the ground to the trans. tail shaft, and from the ground to the front of the crankshaft, the trans. should be higher.

[garagedoordennis]

Be sure that the pinion is nosed down and the crankshaft is sloped down from rear to front, or you will get a jump rope effect! Measure from the ground to the trans. tail shaft, and from the ground to the front of the crankshaft, the trans. should be higher.

My pinion is down 6 degrees.....and if im understanding you my center of my tail shaft is 14 1/4" from the floor and center of my crank from the floor is 17". The tail shaft though is 3 degees out the trans