locating drivetrain vibration.

[YellowThumper]

Check the driveline angle , some of th Tremec installs created nasty driveline angles

How many degrees do you recommend and what do you compare it too ?  Also, something thats always confused me. Back in the day when we used air shocks, why didn't that create vibration due to angle changing ?

Raising car will change front to rear angles proportionally. They cancel each other out if all was originally factory setup.
Lowering can affect it because even though angle change is equal, you are removing the required angles.
When angle on one end only is changed, that creates mismatch.

My offering is also your U joints. They could be worn as discussed.
I have also seen them get rusty inside to where it would no longer swivel smoothly. Every time it hits the tight spot will throw it off.

[Racer57]

Check the driveline angle , some of th Tremec installs created nasty driveline angles

How many degrees do you recommend and what do you compare it too ?  Also, something thats always confused me. Back in the day when we used air shocks, why didn't that create vibration due to angle changing ?

Raising car will change front to rear angles proportionally. They cancel each other out if all was originally factory setup.
Lowering can affect it because even though angle change is equal, you are removing the required angles.
When angle on one end only is changed, that creates mismatch.

My offering is also your U joints. They could be worn as discussed.
I have also seen them get rusty inside to where it would no longer swivel smoothly. Every time it hits the tight spot will throw it off.

My thought is that when using air shocks, your raising the tranny which is attached to the frame, but the differential stays the same. So, creating more angle doesn't effect it, but less does ?

[Bullitt-]

Your looking for parallel transmission & differential
strive for between 1* and 3* degrees between the transmission yoke (or flange) and driveshaft, and 1* to 3* degrees between the driveshaft and pinion

https://www.therangerstation.com/tech_library/pinionangles.shtml

[Chryco Psycho]

https://www.youtube.com/watch?v=Idk3BVDVHq4

[Katfish]

That's a GREAT video!
Thx for posting, simple and to the point.

[dodj]

  I had a bad vibration mid-speeds and turned out to be the crankshaft pulley.  It was a pulley for 3 belts (maybe AC?) whereas I had 2 belts.

I haven't been able to get high speed vibe out of my car for a while either. Like above 65. Maybe it's my pulleys.Seems more in the front than the back.

Well I examined my fan pulley on the water pump and it has a definite wobble in it. It'll surprise me if that's been the vibe all along..but I'll find a replacement and give it a whirl.

[usraptor]

When I restored my 70 Cuda I refurbished or replaced ever nut, bolt, washer, part etc. on that car except the U-joints.  When I took it in to have it dyno'd, the technician shut it down because of a vibration at 4800 RPM that I embarrassingly had never noticed.  New U-joint solved the vibration issue. 

[Racer57]

Your looking for parallel transmission & differential
strive for between 1* and 3* degrees between the transmission yoke (or flange) and driveshaft, and 1* to 3* degrees between the driveshaft and pinion

https://www.therangerstation.com/tech_library/pinionangles.shtml

That diagram doesn't address what I've been wondering about. When air shocks are used, the transmission will raise up, but the differential stays flat.  It has been decades since I used them, but I don't remember any vibration.