How much should the slip yoke be into the transmission? I have 1=5/8" remaining after it is in, is this far enough? I can't find out what the length of the shaft should be as I have a 72 Cuda 340/904 with 8-3/4 rear and all literature does not address this combo.

shove the yoke all the way in till it bottoms out

measure the center of yoke to center of yoke on rear axle

subtract 1 inch..thats the length drive shaft you need and the slip yoke will be in the correct operating zone

IMO..no its not to short

vibs can be a few things...

has it been cut?

does it have weld on weights missing? (look for spots that a tac weld has been there)

does it have any dings/dents/bent in the shaft?

are the yokes in good shape?

(caps need to be tight in the yoke and not spinning)

you can have it balenced fairly cheap and is good $ spent in the long run

how is the tailshaft bushing in the tranz itself?

I've posted the vibration thing a couple of times, driveshaft has been recently balanced. It was suggested by some to check the drivshaft length, which I am doing with this post. Others said to replace the tailshaft bushing and bearing which is my next project. I just want to make sure the 1/2" doesn't make a difference before I proceed with the bushing etc. including replacing the slip yoke.

I have used a seal with dust boot and cut the drive shaft

shoved all the way in and subtraced 1.5 inches with no problem

1/2" should be fine IMO

I have had them up to 2" from bottoming the yoke,dont remeber haveing any trouble with it either

but the 1" is rule of thumb and 1.5 is not that much more

I measured mine with the dust boot on, should I remove it and measure it?

Jon, I just had a new shaft made yesterday. If you go to Dennysdriveshafts, they have a form you can print off that tells you clearly how to properly measure for driveshaft length. I used it just to double check myself, and I filled it out and took it to my local D/S maker and they appreciated having a sheet that clearly spelled out what they needed to do! Just my .02. Lee.

Why not just put up the link?

Dennys Driveshafts - How to Measure Correctly