47-55.1 Driveshaft measurement

[Matt_50]

Just double checking some info.

For my 1950 Chevy 3100. 350/th350 with 10 bolt rear end. Leaf spring suspension.

I took the slip yoke off my driveshaft and took it with me to the driveshaft shop. I explained what I had and he said to bottom out the yoke, pull out 1 inch, and measure center to center of U joints. This sound good?

I don't need the truck on the ground do I? If both front and rear are on jack stands?

[Matt_50]

I think my biggest worry is seeing that measurements must be within 1/16 of an inch. Id hate to get something off.

[mongocanfly]

The full truck weight needs to be on the springs...as long as your jackstands are under the axles it would be the same as it sitting on the ground...

[joedoh]

dont worry about 1/16, or even a full inch. I do almost an inch and a half of stickout in case someone lowers the truck down the road. the slip yoke should have a good 5 inches of spline, naturally you want as much as you can have in the trans but a half inch wont kill anything.

Originally Posted by mongocanfly

The full truck weight needs to be on the springs...as long as your jackstands are under the axles it would be the same as it sitting on the ground...

this is correct. truck on ground, full weight, most leafs arc forward for power transfer and if you measure with the springs slack the driveshaft will be too long.

[Matt_50]

What's the max amount a slip yoke can be pulled out when measuring for a driveshaft?

[joedoh]

i usually do 1-2", usually 1.5

[Matt_50]

I don't plan on any future height adjustments but you never know. If I did 1.5 inches instead of the 1 inch the shop said...

That'll be OK?

Here's my yoke.

[joedoh]

yep should be fine, the more spline engagement the better but the reason for the stickout is for cycling the suspension: you may not plan to lower it but bumps and turns will "lower" the suspension. not enough stickout means the yoke will break the tailshaft.

[MiraclePieCo]

Originally Posted by Matt_50

I don't plan on any future height adjustments but you never know. If I did 1.5 inches instead of the 1 inch the shop said...

That'll be OK?

That 1-inch measurement that some shops recommend has gotten me in trouble - a couple of times I was about 1/16" from being able to get my shaft installed! Nowadays I go 1-1/4" Your 1-1/2" should be fine.

[Matt_50]

I cut the difference, 1 1/4 inch.


I taped a ruler to the transmission. Marked both it and the yoke. Pulled it out to my mark. Through the middle of the U joint I was able to slide a cotter pin to mark center. Then I went to the axle. Marked center of U joint. At that mark I put the edge of a magnet. I then found an extra tape measure. Made sure the tab wasn't loose and made sure the tab didn't mess up the measurement. I cut the measuring tape at about 55 inches. Easier to handle with the reel off. I then butted the tab of the measuring tape against the magnet and used the pin in the yoke to get measurement. Checked both sides. 51 3/8.

[mongocanfly]

are both your yokes lined up when you measure?

[Matt_50]

Yep, as best I could.

[mongocanfly]

should be good then...