Wouldn’t ya know it???? 3:73 gears and car runs like a scalded dog ( am I allowed to say that still?) and if I were a law abiding citizen, I would never know this problem with exists!!! Anyone see where I’m going with this yet????
Let’s just say hypothetically of course, that if I were to drive at say 85 mph, I get a harmonic vibration! Looks like I need to get get driveshaft rebalanced, came pre balanced when I bought it, but now it’s spinning quite a bit faster at any given speed, so maybe the balance was as good as I thought!! Oh well, it’s only money!

 

Never tried this. No need! I am happy with the 2.88 !
It is an extrapolation from a "cure" for an engine vibraton.
Not sure as to the application to a two piece drive shaft

1. Clock the sahft a quarter turn. Drive it. Vibrates? repeat as necessary.
may fx or may make it worse!!

2 On a lift. \\A. Examine for missing weight.
B. Add a hose clamp. sin the shaft at road speed. Alter for four different positions fix or worse.
C. Use a dial indicator or merely a pointer. rotate to check for run out.
D. Check the ujints. About 6 of \em

Carl ,

 

Wish I had the 3.73's or 3.90 with the 700R4. I have 3.54's. One piece shaft and I shift at 6250. No vibration. Scenery does come up quickly. As you say "Scalded Dog".

 

You might be getting close to the critical speed of the driveshaft, that will cause it to vibrate. Spicer have online calculators to determine the critical speed. What is the condition of your centre bearing? That is a bearing mounted in rubber, the rubber can deteriorate and allow the driveshaft to move around. That will affect the driveline angles, plus cause vibration itself.

I can't remember, do you have the original engine and transmission or is the car lumped? If it's lumped, have you ensured that all the driveline angles across the U joints are correct, including the calculating the compound angle in both the vertical and horizontal planes?. Have you calculated the difference between angles at each end of a shaft section (and the compound angle) and ensured the variance from one end to the other is no more than 0.5°? If the angles are not correct, then you will notice the vibration more at higher driveshaft speed due to the different axle ratio.

 

I have 3:73 and had 3:54 and always had a vibration until I went back to a 2 piece driveshaft. Far smoother with a 2 piece. Jag used a 2 piece for a reason when the car was developed in the late 60's . The diff ratios were in the 3's then so thats how the car was developed.

 

Are the UJs correctly aligned, same orientation and angles at each end?