What does driveshaft vibration feel like?

[thegreatjustino]

A few weeks ago I installed an NP435 transmission. Still using the Dana 20. I have a 3-1/2" BC lift that I have put over 1000 miles on in the last couple of years with the stock 3 speed and Dana 20. After installing the 435 which I know is slightly longer than the three speed, I have a very bad vibration in my drivetrain that comes and goes periodically. Once it starts, it usually won't stop until I come to a complete stop. Pushing in the clutch does not stop it, coasting with the transmission in neutral doesn't stop it. It did happen on the freeway a couple of nights ago, and it did eventually stop on it's own before I could pull off. If I give the engine gas while the vibration is there, the Bronco will accelerate, so it doesn't seem to have any effect on performance. I'm trying to determine if it is something in the transmission I installed, or just my driveshaft (or perhaps something else altogether). Thoughts, pointers, and ideas appreciated.

 

[73Russell]

Does the vibration slow as you slow?
I am guessing that you probably have a balance issue and not a driveline issue, I know mine came on fast and only got worse never went away.

 

[thegreatjustino]

Does the vibration slow as you slow?

Been a couple of days since I drove my Bronco, but as I recall it doesn't. I want to say that it seems to be a consistent speed whether I speed up or slow down. Now I am scratching my head even more after realizing that.

 

[carter2772]

Did you use the same drive line? If the new tranny is longer i would think it would affect drive line.. I am no expert but i think i remember reading something about lifting trucks, witch changes the distance between t case and axle housing, and how it can affect the slipping part of the drive line and almost bind the two parts of the drive line and cause vibration. Make sense? Just a thought....

 

[TN1776]

Which NP435 adapter did you use?
I used the adapter from Tom's and the combined length of the 435+D20 is nearly identical to that of the original 3-speed and D20 (I'd say within 1/4"). I'd say measure your driveline angle in relation to the pinion angle and see if its within acceptable tolerances, and if not it might be time to shim your axle to correct it.

 

[Broncobowsher]

Driveline vibration is a high speed vibration, like a paint shaker (speed wise, hopefully not intensity wise). Directly related to speed but intensity may vary with load (accel/coast/decel). About 4 times faster vibrations then a bad tire. Usually felt through the floor and/or shifter.

 

[Madgyver]

Ask Bax................... He Knows it well............

http://classicbroncos.com/forums/showthread.php?t=123270&highlight=driveshaft