Turbo 400 yoke troubles

Ok so this 1970 350GS with turbo 400 is in my shop for leaking rear seal.

Cars weight is on jack stands on rear axle.
I pulled driveshaft out and noticed yoke is grooved really bad, so I ordered new yoke 6.75 to match old yoke that on driveshaft. So I ordered a new one $149
Once I got yoke and new seal installed I noticed driveshaft was way to short, 53” c to c.
Since I know the car needs a 55” c to c shaft I changed it out, so now my problem is, the yoke bottoms out in tranny and there’s no play in it.

so my question is, was this 6.75 yoke not meant for a 70 Buick with a 55” shaft?
Because I think I need the 5.5 yoke now.

 

Mine had the 5.5” barrel. My guess is someone got the longer one previously to try and compensate for the shorter shaft.
With the suspension under load,and the yoke bottomed-our into the transmission,you need to be able to pull it out 1 1/4” to seat the rear u-joint into the rearend yoke.
The other problem with some of those longer-barrel yokes is that they are not splined to the end,which doesn’t give you a lot of spline engagement if the yoke is pulled out to far.

 

It’s just crazy how many variables there are

 

You sure got that right! at times it can be overwhelming. Ordering a part becomes a second guessing war wondering if yu are doing the wrong thing.

 

But all those wrong parts come in handy as paper weights to hold down all the notes on the wrong parts not to order again. Yep...

 

TH 400’s have many variables depending on tailshaft length and also car vs truck trans. Always make sure you can bury the yoke into the transmission regardless of the trans you are dealing with. You should see very little of the barrel if any at all. Then pull it outward 3/4 to 1”. This is a general rule of thumb per most DL shops. Again depending on your vehicles trans. At this point with the rear diff supported (not hanging) measure for the driveshaft universal joint center to center length by going from the trans yoke to the differential yoke. Really as simple as that. Last but not least, ALL OEM prop shafts are assembly balanced. When you change a component, any component on a shaft then you change the balance! An out of balance shaft wreaks havoc on tranny seals, bushings, universals etc. Just an FYI

 

Good thing is you should be able to shorten the new shaft for manimal expense and get what you need