Here is the 12 minutes of GoPro footage. Don't know what the slow grinding noise is and my eyes see a in and out movement at high speeds. Not sure what's normal

Pretty long idle out to the road before I'm able to get on it and that horrible grind stops....... Ideas? Never knew that was there until the GoPro was mounted right up against the back of the tranny mount

 

I don't have time to watch 12 minutes of a shaft spinning. Do you have a time frame in the video where the problem is happening?

 

7:50 and 9:35 gives a quick sound of it. I gotta wait until I can get it stretched out on the highway to hold it there a longer spell.
The first 40 seconds demonstrates the screeching sound that goes away as soon as I speed up.

Sorry for the length, didn't think about people having to suffer through that long. It was exciting for me because I actually had footage.
I was also recording engine data with my laptop with the eehack program so that was another reason for the duration.

 

Ok, I tried to make this one short and sweet. Is this too much play in the tail shaft?
Thanks for any comments offered
Smoove

 

I'd think that is fine as the driveshaft is meant to slide along the tail shaft of the transmission as the suspension moves.

I'd be more worried about the pinion gear lash in the rear end. You may tug on the yoke that the drive shaft attaches to and see how much it moves. That should be the "solid" point of attachment.

 

Ok thanks. I went ahead and pulled the extension housing off and going to replace the bushing and seal. Less than $20 , couldn't hurt plus I'm learning something new.
The yoke in the rear has counter and clockwise movement but no up down, left right or in and out play.
I will make a short video to get your opinion anyway because I don't know what should or shouldn't be there.

 

A glimpse at seal and bushing



Tranny with the extension housing off

 

Here's the rear yoke play. IMO looks, feels good

 

^ That looks good.

 

Thank you sir. I noticed while pulling extension housing off the stock Trans mount had been replaced with an energy suspension one. Could this have changed my pinion angle?
Regardless, I already ordered an AC Delco rubber mount to get it back to stock.

Seal and bushing out of housing, now wait till Monday to find a Trans shop to install a new one.
Trudging forward......

 

^^ i think thats your issue. just last week i was browsing through this forum and another fella has the exact issue you are. actually, his was motor mounts. he replaced his and it threw off the angle of everything.

let me dig around and try and find that post and i'll share it with ya

 

maybe this will help:
https://ls1tech.com/forums/gears-axl...vibration.html

 

Hey Smoove. I saw you pushing the trans. tail shaft around & I bet that is your issue. Or most of it. Hope you get it taken care of.

 

Thanks for the link: I have read that before and I have a buddy who is going to help me with mine. The numbers and degrees thing is confusing to me.

So here is an update on where I'm at. I will post 2 short videos of what I saw. First the extension housing bushing replacement went well. The yoke slid in tight and was snug with very minimal play, almost none.
I put it in gear, idling and slid under to see if I did good on my seal replacement. To my horror the yoke was wobbling like crazy! I snatched it back off and took it to my clutch and power train shop for testing.
Meanwhile I put the car in gear, idling and looked at the rear tail shaft expecting to see it wobbling, but it looked like butter.
So my shop calls and tells me the DS checked out fine. I sent him my shaft video and he thinks it may be the inside of the yoke. So they are putting a new yoke on and I pick up tomorrow.
Here's the vids......

And thanks for the input guys. I'm gonna get this vibration gone before the new engine goes in!

 

 

 

Finally! The new yoke / stock tranny mount and tail shaft extension housing bushing replacement appears to have worked its magic.
125mph and absolutely zero vibrations!
Thanks for guys who gave input and advice. Hopefully somebody can benefit from my trials and tribulations in their quest for vibration issues.

Next up: motor rebuild

 

lol So we now know exactly which part was creating the problem.

I expect the yoke was the main culprit. Did that come with your new drive shaft or was it stock?

 

It was stock. I only got the DS balanced with new u joints. Glad it's over

 

Congrats on tracking your vibration down, thank you for sharing all the findings and info.
I am in the same boat with my Z28 that has been 4L80 swapped.
I can't even drive the F1 Procharged Beast because of the vibration is painful it's so bad .
I'm definitely going to verify the drive shaft yoke is more like your after video . 👍🏽👍🏽