Chasing A nasty vibration in my drivetrain.

[Average Joe]

Hey Guys, I am chasing a nasty vibration in my drivetrain.Seeing if anyone else has gone through this.
Been trying to get down to the track but have been working out all the bugs in the car.
So when I am under heavy throttle in third gear about 4500 rpm to 6000 its start to get pretty nasty.
I just had the 489 redone with a eaton trutrac so I think I am good there. I am taking the driveshaft down today and having it checked for balance.
The only thing else I can think of is pinion angle.I set it at 0 when I welded the four link brackets on but not zero to the transmission angle.It looks like I should be setting with the transmission angle.Not sure what angle to have it at.
Thanks for any advise.Joe

 

[super-bee_ski]

Or:
-A U-joint?
-Wheel balance?

 

[Budnicks]

the pinion & trans should be close to a parallel/same angles
& the drive shaft slightly different for proper universal wear

 

[rscurtis]

You won't feel a pinion angle problem at speed, you'll notice it as a launch shudder. Look for something out of true or out of balance.

 

[HYRDGOON]

Hey Joe,

Devin (747Mopar) has been dealing with some vibration issues and some good info in this thread http://www.forbbodiesonly.com/moparforum/showthread.php?90741-Pinion-angles

Although I read yesterday he things it may be down to mismatched arch in the springs and is having one spring de-arched but you're coil-over aren't you?

 

[747mopar]

Going threw the same thing only mine is totally different (vibrates when the shaft is in a coast mode). I'll tell you what I've learned, like Bud said shoot for a parallel pinion and tranny angle with some angle left in the shaft angle. Here's a link to a cool app from Tremec for smartphones that turns your phone into a cool tool, it will measure all three angles and show incorrect angles as red and correct as green (seems pretty accurate when checked against an angle finder) http://www.tremec.com/not_am_detalle.php?m=355. Check universals as stated, make sure to check your slip yoke slop, loose mounts or bolts and make sure your tranny isn't touching the body anywhere. Also depending on your universal joints some caps have different thickness C clips using the incorrect clip will allow the joint to move back and forth in the cups. I think I've tracked mine down to my leaf springs but won't know until the weekend which doesn't apply to you. It's a process of elimination that can drive you mad so just correct everything as you go.

 

[Average Joe]

Thank you guys I really appreciate the advise.
I took the driveshaft down to driveline specialties in the springs.Turns out when Keisler built the driveshaft they put in the wrong universal joint.So the u-joint they put in was to small.I didn't notice it when I put it in the first time.But tonight when I put the correct one in I had to file the pinion yoke a little where the u-bolts go through. The u-bolts warped the metal around the smaller caps.
I followed the diagrams from your post Budnicks and set the angle up at 1 degree difference. The trans is 4 degree down and I put the axle pinion three degrees up for 1 degree of twist with the four link.With correct angle and correct U-Joint I am ready for some more testing.I hope the weather clears up this week so I can get some road time in.

 

[747mopar]

4 deegrees seams like allot of angle, I tried to match the factory setup on mine and have the tranny at 2.5 degrees down and pinion up 1 degree which is untouched. I guess the important thing is the difference between the 2. Good luck, hope it works out for you.

 

[jfreakofkorn]

I would replace the u joint(s) first ..

than I would look into balancing the drive shaft ...

 

[swampdonkey]

My pinion snubber was to long, had an awful vibration under hard acceleration and so only thing it could be was the newly fabricated snubber I welded up was 1/2" to long so I cut off 1/2" ans the aweful vibration was gone.

 

[Average Joe]

My pinion snubber was to long, had an awful vibration under hard acceleration and so only thing it could be was the newly fabricated snubber I welded up was 1/2" to long so I cut off 1/2" ans the aweful vibration was gone.

Awesome! Glad it was any easy fix.
After I changed the u-joint the violent shake was gone.I still get a little vibration on the highway but it changes at different speeds so I think that is in the tires.
I ve had the car down the strip since then and it went well so I think I have that bug worked out.
Thanks,Joe

 

[satman72]

Don't be too quick to fix it. Your wife or girlfriend might like it!