Did a swap from a turbo 350 to a turbo 400 along with yokes of course (was a bolt in turbo 400)... Went to 1350 yokes on both ends (12 bolt rear end also)... Had the drive shaft built after what I thought was good close measuring... This is a 69 C10 with the ladder type rear suspension and is lowered approx 2 1/2 inches from stock height so not alot of travel is left...

How much travel in the yoke do I need...? As of right now I have about 1/2" before it bottoms out... I do not carry anything but race the truck (has a BBC powering it approx 450hp)...

Recommendations...?

I would recommend at least 1/4 inch from bottomed out at its deepest point for engine mount flex.

Since you have that suspension lowered that much here's what I would do if it were mine...
I would unbolt the rear joint, push the yoke into the trans all the way and measure how far the yoke arm is from the tailshaft with the arm horizontal.
Rebolt the rear joint and then load the truck to full suspension travel.
Measure the points again and see how much is left..... I would like to see that 1/4 inch for rubber engine mount flex.

Put chassis (frame) on stands (4) places and let rear end drop to its lowest point and see if you still got clearance.
I have run some 4 link applictions with no more than 1/2 in.

Thanks on the replies... Will be checking several ways this afternoon after the dinner wears off... (if I can get under it again...?)

Here's a link to a driveline shop's recomendations:
http://www.iedls.com/measure.html

HTH,
Don

He is worried about the yoke bottoming out in the transmission. Not falling out into the floor.

That only works IF they are supplying the entire shaft AND the front yoke... which they are....... yokes might vary as to depth on the trans shaft, that is, the distance from the tail shaft end to the u-joint centerline.

With an existing yoke, you push it in all the way and measure center of the front u-joint to the center of the rear U-joint, then subtract for the desired clearance.

my driveshaft guy say's to bottom the yoke out then pull it out 1", measure center of yokes as a final measurment.

That is what I said in my last post, except I said ----- bottom it, measure, then subtract the desired clearance from your measurement.

1" clearance where/when ?? (it constantly changes during suspension travel).... at ride height or when the suspension is loaded for the driveshaft to be pushed into the transmission as far as it might??
The only reason the clearance is there is to prevent the yoke from bottoming out in the transmission, which is Bump's concern.

I have seen people measure at ride height and add that inch on a short yoke and when the suspension unloaded the yoke was so far out it twisted on the trans splines, cracked the yoke which angled off a few degrees and the front of the driveshaft flew out just like it had broken a front joint... Oh Oh..... some identical looking yokes have shorter splines inside. You want as much spline contact as possible for strength.

BUMPSTICK has a close clearance at ride height and needs to know if suspension travel will bottom it out into the transmission. Hence he has to load the truck down.

He might end up having to shorten the driveshaft 1/2 inch.....

FOOD>>> FOOD>>>