Driveshaft Confusion

[PurpleBeeper]

My car is a 70 Roadrunner 383 4-speed 8-3/4 car with the large U-joint drive shaft originally. The original drive shaft is long gone. It now has a 440 and a '67 4-speed in it.

I've been running a small u-joint driveshaft (small/large conversion rear u-joint) I pulled years ago from I think was a 400 auto '73/'74 Satelite. This driveshaft measures about 50-1/2" center-to-center. (BOTTOM PIC) I also added old 3800 lbs/4-speed super stock springs.

Based on the wear pattern on the front yoke and how far the yoke sticks out of the trans it "looks" about 2" too short.

So, I got a '69 Roadrunner large u-joint drive shaft that measures about 52" center-to-center (TOP PIC). BUT when I tried to install it the front yoke won't slide into the trans far enough for me to get it into the rear end yoke. The '73/'74 front yoke slides in the trans to "the hilt" but the '69 front yoke bottoms out in trans about 1/2 way in (not far enough to get the slack I need to bolt it to the rear end).

What gives and what do I do? :tard:

 

[Supershafts]

How much of the slip yoke is in the trans, detroit made hundreds of different slips and there are different output shafts for the 727.

What is in the trans and what is the overall length of the slip yokes bearing surface.

Or switch the slips from one shaft to the other and have it balanced.

I would also lose all that old detroit shaft, reuse the slip but lose the rest of that shaft

 

[HitIt]

Just wondering if you get any vibrations from that input not being in far enough. I think it mostly would be noticeable at low speeds and from a dead stop. Thanks.

 

[67 coronet]

i would have a new shaft made by a drive line shop.they will tell you exactly how to measure the lengths required.just reuse the slip yolk that fits best.

 

[Meep-Meep]

In my experience the yokes slide all the way up until they bottom out and none of the tube is visible. Then when attaching to the rear yoke you would pull the shaft out of the tranny an inch or so and that's that. What you show in the bottom pic is definitely not right and you know that. Nothing inside the tube preventing engagement? There is usually a freeze plug thing that caps off the end of the tube by the U joint and I wonder if something is going on there. What about the tail shaft bushing? Spline count and size is correct? Just throwing stuff out....

 

[Resto]

I had the same problem on my '68 Barracuda. The 833 output shaft was profiled such that my slip yoke had to be machined internally to remove the spline a couple of inches in.

 

[PurpleBeeper]

In my experience the yokes slide all the way up until they bottom out and none of the tube is visible. Then when attaching to the rear yoke you would pull the shaft out of the tranny an inch or so and that's that. What you show in the bottom pic is definitely not right and you know that. Nothing inside the tube preventing engagement? There is usually a freeze plug thing that caps off the end of the tube by the U joint and I wonder if something is going on there. What about the tail shaft bushing? Spline count and size is correct? Just throwing stuff out....

OK, brain fart! Thanks Meep-Meep for pointing out the obvious (that I missed)

The top pic driveshaft/yoke ('69 Roadrunner) DOES go all the way in & the extra length fixed my problem. It seems I had some "gunk"/rust, etc. and too much wheel bearing grease inside the yoke that was causing it to hang up sliding onto/into the tail shaft. Problem solved! :grin:

Thanks Everyone!

 

[PurpleBeeper]

Just wondering if you get any vibrations from that input not being in far enough. I think it mostly would be noticeable at low speeds and from a dead stop. Thanks.

You're right HitIt! When I would push the clutch in the driveshaft would wobble so hard it would smack the driveshaft safety loop. It sounded like my clutch was having a very bad day. I'm definitely glad I didn't have to pull the trans to fix it!
Thanks!

 

[bigmanjbmopar]

I was going to say you can just buy a 69 road runnet lol ooh i just did haha