[runningman]

After several years of procrastination I'm finally doing the auto to 4 speed muncie swap on my 67 GTO. I've seen the driveshaft scenario covered several times here with the answer usually being the TH400 driveshaft is simply "too short" to use. So doing some simple math the TH400 u-joint center-to-center dimension is 59.34" long. The factory assembly manual states the M20 driveshaft is 60.00" with a 4.95" yoke so a total length of 64.95". Using a Neapco N3R-3-6081X yoke that's 5.50" long makes the TH400 driveshaft 64.84" - less than an 1/8" shorter than the "60 inch" M20 driveshaft.

So question is does this slightly shorter 1/8" length matter? Does it matter the u-joint sits back roughly 5/8" more from the tranny?

The fact I couldn't find this outlined on the forum anywhere makes me think I might be missing something.

thanks in advance for the comments....