Driveshaft length.... slip yoke movement inside trans.

[bugdewde]

If you've seen my project journal on the '72 Kammback, you know I need a custom length driveshaft. I'm familiar with the lengths posted in the FAQ, but it appears those lengths won't work with the 215 V8, custom trans crossmember, T50 and the 7.5" rear.

So, how much of the slip yoke goes into the trans?

One thought says 1/2 of it, allowing equal amounts of in/out travel with suspension travel.
But another thought is 1/2 travel out would be catastrophic..... maybe more spline engagement is used (IN) and the travel in/out is less than 1/2 the slip yoke length.
Then I'm thinking at full droop (on lift), at least 1" of spline should be minimum. To be safe. Would that allow ample inward movement?
Is there a standard rule?

Just figured I'd run it by you board members before heading to a driveshaft shop that may not be familiar with the suspension movements/travel of an old H-body.

[cjbiagi]

Basically you want it 3/4" from bottoming out in the trans with the car and suspension at normal ride height, no more than 1".

This is from Denny's Driveshaft site.
How much slip travel should I have?

In most applications the minimum is 3/4 inch and more than 1 inch is not necessary. This is measured with the rear suspension supported on safety stands or with the rear end on the ground.

Or
With the weight on the rear you should be able to slide the yoke in no more than 3/4" - 1". More than that and it will wobble & damage the output shaft

[bugdewde]

Thanks, Clyde.
Didn't know if h-bodies were the exception to the norm. Gotta get down to the car and do some measuring today.

[chevyart]

3/4" is the norm for factory suspensions. you only need to back off a 1/2" if it is a race car with ladder bars or 4 links. the rear dont move in or out that much on the race cars with the above mentioned type suspensions. art