Okay, I have changed a bunch of **** and now I have a fast vibration that starts at 55MPH and stays rather steady on up or so. I can feel it in the seat of the pants real well. Smooth as silk under 55MPH.

I recently replaced the R&P. Doubt its that.
I recently replaced all brake rotors. Doubt its those.
I had the driveshaft balanced. Dead nuts on so I doubt its that.

I recently had all new tires installed. Maybe its the tires. I will take it to the shop to be checked ASAP.

I recently tweaked my pinion angle, its now at 2 degress (pinion down). I tried different pinion angles and nothing reduced the vibes.

Thoughts?

 

weight came off the DS?? Or tires out of balance? Hit any big pot holes lately???

 

ujoints.....
and what r&p

 

Driveshaft was balanced by a local semi machine shop. The rear u-joint was suspect and replaced. It was then rebalanced and checked out absolutely perfect. Weights are intact. I must assume its not the driveshaft.

 

Hmmmm possibly something in the clutch or flywheel? Was it fine B4 you messed with the pinion angle?

 

From what I recall, yes. I have jacked with the angle for hours. I can make the problem worse with pinion angle and then make it better but not cure the problem. Dont see it being clutch.

Again the tires are brand new and I just recently had it over 50 after getting them installed.

What do unbalanced tires feel like. High frequency vibes?

 

When i was gettin vibrations it was my tires so definitely have those checked. Did you get directionals? maybe they put them on in the opposite direction. That was what happened to me. good luck though, vibrations suck

 

Yes, they will be higher pitched/frequency vibrations if it is the tires. Its sometimes like a howl.

 

I had the tires checked, they are balanced.

Its definitely drivline angle. I had it right a while back but monkey'ed with it to troubleshoot gear whine. Now its just being a MF getting it back right.

 

buy a pinion angle measure....remeasure and repost the results

 

problem with that is every car is different and he has a MW Fab 9!
I took off my adjustable TA, and went back to a NON Adjustable. No More vibrations here!!!!!!! I could get the Adjustable good some days and it sucked on others! LOL!

 

I have stock length NON adjustable tubular LCA's already. I also have the magnetic angle finder. I did it once, so I should be able to do it again once I have the whole car off the ground to get access to everything. Of course I will have the jackstands under the rear axle tubes to load the suspension.

 

I would put the car on ramps then jack up the other side and use ramps there too. That way its level and loaded. You have no idea how many times I changed mine while the car was on the ground( I used to keep an angle finder and wrenches in the car LOL). I hated it so much I bought 4 ramps. Makes life so much easier

 

I hear ya' about the four ramps.

My plan is jackstands under the tubes, wheels off the ground and running the drivetrain in place to test for vibes so I dont have to keep dropping and driving it.

 

Think you be able too tell?

 

Hope so. Right now the think feels like its going to explode at 60MPH. Definitely way off as of now.

 

Just checked the two u-joint angles and they were bad mismatched. No surprise there.

I have now adjusted the TA so that the (pinion to DS) and the (tranny shaft to DS) angles are the exact same or parallel. This gives me a 4 degree angle on each end of the DS. Did this with a magnetic angle finder and a bubble level.

Drive shaft is 0 degrees on the guage. Pinion is +4 (down from DS) degrees and tranny shaft is -4 (up from DS) degrees.

Have not driven it yet. Hope this helps.

 

Its very hard to say whats right since you have the Fab 9. Drive that sucker and let us know. https://ls1tech.com/forums/gears-axl...le-9-inch.html
I went back to a UMI NON Adjustable and no longer have these problems.

 

Update.
After continued frustration following the instructions provided on the net, I decided to simply revert back to what has always worked for me when I had I had a 4" jacked Jeep wrangler with a 24" long drive shaft and 13 degree u-joint angles. Anyone who has ever been down that road knows the PITA that is to correct.

What I always did on my Jeep was ensure that the tranny output shaft and the pinion were absolutely parallel and to hell what the driveline angles are.

It has alway been my understanding that if both u-joint angles are equal then there can be no vibes due to cancellation. Also if the two angles are equal then the tranny output shaft and the pinion must be parallel. When one u-joint angle is 2 degrees and the other is 4 degrees then its vibration city due to the tranny output shaft and pinion NOT being parallel.

So what I did was toss the angle finder and get out the adjustable bubble level. I placed it on the front of the harmonic balancer and adjusted the the bubble to centered on the dial. Of course we all know that the crank and tranny output shaft must be parallel so this was the easiest place to get the reading from. I then took the bubble level and placed it on the face of the rear end housing where the gear case bolts up. I then simply adjusted the TA till the bubble was centered. The tranny output shaft and the pinion are now absolutely parallel.

I got the angle finder out to see what the driveline angles were now measuring out at, and they were both sitting on +3 & -3 degrees and the drive shaft was sitting on 0. This is exactly how I set the driveline angles on my Jeep and it never failed then.

I drove the car and 90% of all the vibes were gone, especially the vibe that prevented me from going over 60MPH cause it felt like the car was going to explode. I know that if it ain't dead nuts on right now, then it must be very close. At the very least, it is now drivable.

I then adjusted the pinion both up and down a single degree to try to totally dial it in but it made no difference either way so I locked it down and called it quits.

The drive shaft is balanced and the bad u-joint was replaced so I must assume that the DS is not causing the very minor vibe that I still hear and feel. I am also going to assume that the driveline angle is acceptable as well.

What are the other possibilities that might cause a very minor vibe to remain like this?