73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Ronno6 on April 30, 2018, 03:36:19 pm
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I see this question asked somewhat frequently, but never actually answered:
How far should a driveshaft yoke engage the output shaft of the tranny??
Almost without deviation the answer is given in terms or how much yoke should be showing beyond the tail housing seal.
that's all well and good, but does not answer the question.
Haw many inches of engagement should the yoke have on the spline??
For instance, my Muncie M20 is 3" shorter than the TH350 I am replacing.
If I use a driveshaft that is 3" longer than the old one, spline engagement would be the same.
But, If I found a shaft that was only 2 3/4" longer, the yoke engagement would be 1/4" less.
My original setup had about 1 1/2" or travel into the trans when the rear U-joint was disconnected.
That may be a bit much to begin with.
So, I ask: how many inches of spline engagement should a driveshaft yoke have on the splined tailshaft of the transmission????
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About right in the middle at normal ride height.
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Actually, when I rechecked the one at the junk yard, it is exactly 3" longer than mine,
uses the same U-joints (I will replace) and has the correct tranny yoke.
and cost about 20% the cost of having mine re-tubed.
Now, if it is straight.............
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Before I retired, I worked at a GM plant that made driveshafts. That's before front wheel drive.
Anyway, a friend of mine made custom driveshafts there.he made me one for my drag car.
He said to use the proper front slip yoke, slide it all way in, pull out 1". Then measure from center of u-joint to center of rear end yoke u-joint with car sitting on ground. That dimension is how you determine shaft length. Tha 1" dim is for shaft movement caused by road conditions.
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When I removed the shaft, there was about 1 1/2" of travel into the rear of the tranny.
I am having the shaft balanced and the man who knows measured the shiny spot on the yoke
and said I was about 1/2" shy of recommended insertion depth, but he indicated that would not be a problem.
That sounded right based on my eyeball measurement of free travel.