Backstory on this is it was a running and driving 71 Cutlass with a 350/350. The car is pulled apart in the middle of a frame off resto and has had everything rebuilt including the suspension, diff, trans, and engine. I am in the process of reassembling the car now and I have the body tub, engine, trans, and complete suspension reinstalled. I went to install the original rebuilt driveshaft and it will not slide far enough into the trans tailshaft to allow me to slide the rear u-joint in. It bottoms out in the tailshaft with about 3/4"-7/8" of the yoke still exposed and at that distance the ujoint would fit perfectly into the pinion yoke, but it would need to slide in that extra 3/4" forward to be able to go into the pinion. Also worth noting that when I disassembled the drivetrain I didn't pull the driveshaft until the engine and trans were pulled out so I didn't notice if there was an issue then. But I do have pictures of the car together that shows that the driveshaft yoke still had around an 1" exposed from the tailshaft which would be bottomed out currently, but drove fine which makes me think it was not bottomed out.
Questions are; is the yoke supposed to be able to slide completely into the tailshaft? And if so am I installing the driveshaft wrong into the tailshaft (such as missing a keyed slot) or do I have an issue with my trans? If anyone had easy access to a th350 to 8.5 10 bolt drive shaft laying around and could grab measurements I'd greatly appreciate it, looking for the U-joint to U joint measurement and yoke length.

 

There may be a burr or some dirt preventing it from going in further.

 

2piece shaft I assume. Maybe it's separated some and made itself longer?

 

It feels like a solid thunk when its fully seated making me think its making a solid contact when it stops not like a burr would feel.

And yes stock 2 piece, and I thought of that scenario also but I wanted to see if the yoke is supposed to go onto the tailshaft completely and get a measurement before settling on that.

 

I had the same problem with my 71 442, one piece shaft though, and body not on. The driveshaft seemed too long, but it was the lack of weight on the rear springs. Once we pushed down on the back, the angle changed enough to allow the rear joint to go into the rear flange. Yours may be a different issue but be aware of the angles. Your yoke should be able to bottom out into the transmission.

 

Hi
a couple things come to mind
can you supply a center to center measurement on the u joints ,,, ?
did you change rear differentials ?
was the front yoke replaced ?

 

The car is pretty bare bones right now but I can understand the weight, just hard to imagine a few hundred more pounds will get me the 1" I need. And when you say the yoke should be able to bottom out, does it bottom out inside the tailshaft or bottom out from the end of the yoke onto the outside seal?


Measured the center to center and came up with 55.125". This was with a tape measure and me doing it by myself so there it is not the most precise but I read on another post the measurement should be 55.25" so I am not far off and definitely not the 1" I'm missing. Same diff and looked at my receipt from the driveshaft shop and I was only billed for U joints so I am assuming they reused the yoke.

 

If it was made for a T400 then the drive shaft would be too long.

 

The 55.125" measurement matches what I've seen in another post for a th350 driveshaft and the th400 uses a larger diameter yoke so that wouldn't be possible either. I think I have the right driveshaft but I am not sure if its possible if a incorrect longer yoke was swapped in at some point.

 

The yoke should insert all of the way in to the tailshaft. Check inside the yoke for debris. Maybe soak it with some solvent. You shouldn't need to worry about having weight on the back end of the frame.

 

Guess I’ll pull it back out this week and take a look inside the yoke and tail shaft. Hopefully it’s something obvious that I messed when putting it in.

 

A T350 yoke can be put on a T400 drive shaft. Are you sure it came from your car?

 

I know it it’s the same one that came out of the car 5 years ago when I started this process but as fast as being original to the car I have no idea. Wouldn’t the t400 shaft be shorter due to being a longer trans?

 

Brain fart, you are correct.

 

Put a blob of thick grease on the end of the output shaft, reinstall the yoke. If the grease has flatted, you know the yoke is seating fully onto the output shaft. If it doesn’t go in all the way, use a small wire brush to clean the splines. Polish the outer surface of the yoke. Lastly, don’t be afraid to LIGHTLY tap on the yoke to get it to go in. It doesn’t take much surface rust to make things bind up. If it seats with a light tap with a rubber or plastic hammer, it will loosen up with normal driving.

I have a yoke with a broken U-Joint flange that I use to check the fit after bushing replacement. It’s not uncommon to have to give the yoke several firm smacks while turning the yoke 90 degrees. Sometimes if the bushing doesn’t go in straight, or there is a imperfection of the bushing or bore it seats in the yoke won’t want to go in or turn freely. A light “loving” tap solves the problem 99 times out of 100.

 

Well I pulled the driveshaft tonight and looked down into the yoke to check the splines. It looks like the farthest in splines are twisted and don't line up with the splines towards the front of the yoke. No idea how that would happen but it would explain why it wont fully seat on the output shaft, you can see in the second picture that the yoke will only slide in 2.75" inches which is roughly around the same length in as the twisted splines. I am going to try taking it back to the driveshaft shop that rebuilt it and see if they can put a new yoke on for me.

 

Or if they accidentally put the wrong yoke back on your D/S.................