Back in post #106 of this build thread, I show my new driveshaft that I had made for my setup.
Well this driveshaft had issues with vibration. So I sent it back to Denny's driveshaft to get rebalanced. Got it back and it still vibrated.
I ended up installing a Torque arm suspension and aligned my rear differential within half of a degree between the transmission and rear diff pinion. Still vibrated. For months I tried different angle measurements with shims under tranny mount and different angles of my diff pinion. Still vibrated.
So I took the driveshaft off and had it checked locally to see if the shaft vibrated. And yes. It did.
So I sent it back to Denny's Driveshaft and got a full refund.
I then had another driveshaft made using the same design from another driveshaft place that was local. I painted it the same color as my car and even purchased a new Sonnax flange. I was sure that this new second driveshaft was going to be perfect... or so I thought.
Unfortunately it vibrated again. This time the vibration took out my transmissions rear extension housing bushing.
To replace this bushing, its required to replace the entire housing. So I bought a new one along with a new transmission flange for the 6L80e transmission.
Here is what it looks like with extension housing removed from the 6L80e.
Here is the new one installed. I chose NOT to repaint it Red. Working with this part under the car was a royal pain in the behind and I wanted to get this fixed ASAP.
I then moved the slip joint part of the driveshaft to the rear differential side because I did not want to risk my new extension housing failing again.
But of course, the vibration continued but instead of it vibrating on the tranny side, it started to vibrate on the differential side. The vibration followed the slip joint. That lead me to believe it was not my adjustments of angles that was causing the issues with vibration. Its the driveshaft, specifically the slip joint portion of the shaft.
I did lots of research and I came across an article online that lead me to feel confident that it was not my adjustments of angles that was causing the issues with vibration. It had to be the driveshaft itself. Two driveshafts from two different companies had the same problems.
After reading the article, I concluded that its the driveshaft slip that is causing the vibrations. I contacted the Driveshaft Shop and asked about a custom CV driveshaft for my car.
Long story short, I purchased the new CV Driveshaft in 3.5 inch OD 6061 T6 Aluminum with front mounted German made GKN CV Joint from the Driveshaft shop and sent back the red slip joint driveshaft I just bought (and painted) and once again got a full refund.
A month later, the new Aluminum driveshaft came in from the Driveshaft shop and I could not wait to try this out.
This setup was definitely different. It has a new flange adapter setup that connects to the 3 bolt flange of the 6L80e and adapts to the new CV driveshaft. I had to take an allen wrench and modify it so that I could install it to my Nova. For the differential side of the shaft, it uses a 1350 U-Joint.
When installing it, I had to ensure that the driveshaft and the differential pinion was practically in line with each other. Very easy because I already had it set up practically straight with only half of degree. This ensured that the needle bearings of the U joint had some movement for lubrication but yet not move so much. For the transmission side, the CV joint would take care of any angles present, which was only a half of a degree. (Constant Velocity)
Basically I just removed my old driveshaft, and installed this new one without changing a single thing. My settings remained unchanged.
NO MORE VIBRATIONS! This proved to me that it was indeed the old driveshaft's design.
So my advice to all is to just get a CV driveshaft. Worth it!