Sorry but need advice with highway vibration

[Gdub]

So I took as many pictures as I could to show everyone. I uploaded pics of the angle measurements, first pic is ds, then rear yoke flange, then rear of the trans housing. Let me know what you guys think, the angle finder screen was facing drivers side every time.

Also here are some runout readings I got
Drivers side Axles - .003 , axle pushing and pulling in and out was .008,
Passenger side axle .003 , axle pushing and pulling in and out was .006
The trans yoke was .002
Rear yoke setting gauge on the front of the ears, where the bolts screw in, from one side to the other was .013
Rear yoke from the bottom of where the u joint seats in the cup was .018

No sure how to tell if trans is exactly in line with the rear end

Also those readings came off the dial indicator that I uploaded pic of, just to make sure im reading right each / is .001 correct?

Yoke is about 3/4-1" from where it bottoms in trans, pic is hard to read, also the yoke was closer about 1/2 " and still had same issue i just recently moved the rear end back.

[Gdub]

Hey everyone I thought I have done this before and maybe this is my prob but rear end is sitting 1" off center towards the passenger side. I guess this may be my prob?

[Gdub]

Here's another pic everything looks dead straight but like I said whole rear end is 1" to the right.

[andrewb70]

Just because the pinion is offset to one side doesn't mean its wrong. What important is that the rear end is square, so that if looking from the top (or bottom) the pinion and the output shaft of the transmission are parallel.

To me it looks like the driveshaft is way too short. If the front u-joint it too far back it can cause the driveshaft to whip around. This would be felt most when you take the load off it, which is exactly what you described happening. You said that when you put the clutch pedal in you feel the vibration get worse until the car slows down.

Andrew

[SSLance]

I tend to agree with Andrew, that was my first thought when I looked at that pic. How long or how much of the trans yoke is inside the trans?

Is there any up and down movement at the front u-joint? Where the trans joke is not a tight fit into the tailshaft of the trans.

[Gdub]

I can adjust the rear to come closer to the trans and make more of the yoke go into the trans, which is something I already did and did not change a thing. I think next step is to take it to shop for alignment and make sure everything is square.

[andrewb70]

I can adjust the rear to come closer to the trans and make more of the yoke go into the trans, which is something I already did and did not change a thing. I think next step is to take it to shop for alignment and make sure everything is square.

I don't understand how you can move the rear end that much.

Andrew

[mmosley]

I don't understand how you can move the rear end that much.

Andrew

4-link. Shorten all four bars.

[andrewb70]

4-link. Shorten all four bars.

OK, but this is a leaf spring car, right?

Andrew

[mmosley]

I wasn't 100% sure until I read post #38. Yes 4-link. I think it is an RMS set-up. https://www.reillymotorsports.com/st...me.php?cat=263

[Gdub]

Well I cut off the exhaust from mufflers back and vibration is a little better. Comes in around 65 and really gets worse again at 70, all the same issues like before except it did fix my 2000rpm vibration so I'm getting somewhere.

[SSLance]

Curious if you've made any more progress chasing your vibration down.

I stumbled across this video today and it made me think of this thread. Check this out, it's amazing...

[Gdub]

Ok so I cured 90% of the vibration!!! So here's what I found out, check with you driveline shops and make sure they are high speed balancing the shaft!! I had the drive shaft balanced again(the 5th time) and it fixed it. The shop that was balancing the shaft the majority of the time had a 500 rpm conputerized balancer, second place I took it to had one that spun at 4000 rpm, and this was the difference. I ruled out the second company a while back because they did balance the shaft for me once before but I think I had bad pinion angle, then when I changed pinion angle the shaft became too long or short and had to be rebuilt, which I took it to the closer shop which had the low rom balancer.

Still have some drone from exhaust to work out and loose bracket on exhaust but everything else seem to do fine at 80. I will say I have a high rom vib but hopefully that changes with my motor swap this winter. Thanks for everyone's help!



Few tips for anyone searching about driveline or driveshaft or speed vibrations
1.Don't change multiple things at once
2. Write down every combination you try(pinion angles, where shaft was built or balanced, etc)
3. Ask your driveshaft shop what rpm they balance at
4. And good luck!