Determining drive shaft length ?

[Racer57]

I have a Tremec TKO500 and by working with airshocks to change tranny angle and wedges to change differential angle I've gotten the majority of the 70mph vibration out. But there's still a slight rumble when I let off the throttle that I can feel but anyone that's not told about it would ever notice.

Pretending that you do not have a driveshaft, how do you check for the proper driveshaft length ? Once you have that figure, how close does it need to be ? Within 1/4", 1/2",  1" ?

[Racer57]

Anyone ? 

[73_Cuda_4_Me]

Racer57, many on here would not recommend setting tranny angle with air shocks - it makes shock mount the load-bearing point for the whole rearend. They would probably recommend shims on tranny mount to get within specs.

That being said, do you know what yokes you are using? There are different size u-joints used, and that affects final driveshaft length. Larger u-joints = larger yokes/shorter shaft by a bit. I have a 727, so mine won't be similar, but I have about 3/4" yoke showing at tranny seal, sitting on level ground with no load in vehicle.

 

[dodj]

http://www.dennysdriveshaft.com/how_to_measure.html

This is how Denny's says to measure.

[Katfish]

I'd push it all the way in, then pull out 3/4".
+/- 1/2" won't matter