how to measure a driveshaft for shortening?

if you measure from the center of the u-joints /front to back}with the input shaft all the way in - th350- and you get a measure ment of 60 inches how long should you make the driveshaft?

ive heard that you would need to make it 8 1/2 inches to alow 1 1/2 inches of play at the input shaft because of travel issues?

im sure every ones had to stop and think about this at least once. i finaly found a drivshaft long enuff to cut down i dont want to fuck it up


tia

tim

 

Make sure the rear suspension is loaded (like it would be sitting on the ground).

Slide the trans yoke all the way in until it stops, then pull it out ½ - ¾ inch.

Then measure from the u-joint center on the yoke to the u-joint center on the rear end.

 

It's purely subjective, but 1.5" sounds a bit too much, and 0.5" might be too little. In my view, it is desirable to have it in as far as possible without fear of bottoming out. You need to try and calculate how much the joint will slide in use. It would be worth travelling the rear suspension from fully loaded (on the bumpstops) to full rebound (axle hanging) and measuring the distance from the pinion shaft end to the trans output shaft end. Get the min distance, the max distance and the distance at the normal ride height.
Lets say as an example:
Distance at normal ride height:65in
min distance: 64.5 in.
max distance: 65.5 in.
From the above example it would be about right to have the shaft positioned 1" out from the trans at normal ride height. at the other two positions it will have .5" and 1.5" clearance, both reasonable. Most importantly, it will not bottom out.
When you have the ideal dimension you can then deduce the correct length for your prop.
That said, if you dont want to do all the measuring, I'm sure 1-1.25" will be ok!
Mart.

 

I slid the yolk in, backed it out 1" and measured center to center of the U-Joints.

I have done this twice and both worked fine.
TZ

 

I always just call the shop that I am having do the cutting. Everyone I have ever used has done it a different way.....

 

I pulled mine out 1"& it worked fine there should be a "rub" mark on the yoke.put it in to the mark & measure from there
JimV

 

i go to denny's driveshaft website and print out their instuctions on how to measure. there are several different ones,i use B.....then take the filled out sheet and the shaft to the guy who will do the cutting and balancing..usually cost around $135 with new u-joints


if you have access to a big enuff lathe with a steady rest,it's not hard to do yourself,then take it in for balancing

 

When I had my shaft made up the guy at the shop told me to measure the distance between the two bearings with the shaft pushed right in to the gearbox and then take off 3/4"