Thread: How far will front driveshaft yoke slide into turbo 350 tailstock?

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One of those unwritten rules that I have kind of "always known" is that when building a driveshaft, have full weight on vehicle suspension, slide front yoke into tailstock untill 1'' between rear of tailstock and shoulder on yoke, and make that the basis for driveshaft measuring. I did that on my current roadster pickup project, (even made driveshaft 1/8" less than I measured). Tonight when I went to reassemble things, the yoke didn't want to slide in past that 1". It's a good thing that I actually went 1/8" less, or I wouldn't have got the driveshaft to go in.-----Now I'm curious---did somebody change the rules while I wasn't looking, or is it possible that since its an old transmission, the splines have worn to a "set" because it went a zillion miles with that same universal at that particular amount of insertion.---On a new turbo 350 will that front yoke slide in untill the shoulder hits the tailstock, or am I smokin something?

Post removed. Tech and Denny have a simpler solution.

This is an identical front yoke to the one installed---as you can see, the machined surface goes right up to the shoulder, and the internal spline runs another 1/2" past the shoulder on the inside. My trusty tape measure tells me that it is 3 13/16" from the shoulder to the end of the machined surface. Once I get some clear insight into what is actually going on, if my drive shaft is 1/2" too long, I have no reservations about cutting 1/2" off the end of the machined yoke with the air cut-off diamond wheel to give myself the needed clearance.

Denny---It seems logical to me that if the yoke is inserted 1/2" farther into the tailstock than normal, then cutting 1/2" off the inserted end would end up with the same net amount of spline contact.

Denny---tell me more about this short yoke/long yoke business---maybe these 2 yokes aren't as identical as I thought. The one in the picture is the one I used to insert into the tailstock to measure for my driveshaft, exactly as per your drawing.---the one on the driveshaft looked the same but I never actually compared the length of the machined surface between it and the one I measured with.---in fact I didn't know they came in different lengths.

Brian,

I pulled my post. Denny and Tech had better answers.

Cutting it off will work fine - as long as it was the end of the yoke bottoming out and not the trans output spline jamming in the yoke..

Here's what I think happened. Even though the splines go all the way to the shoulder of the yoke, the output shaft of the trans isn't that long, so you bottomed out the end of the yoke inside the trans.

How about carefully inserting a piece of welding rod inside the tailshaft next to the shaft until it bottoms out, then measuring the distance?

How about pulling the driveshaft and comparing both yokes?

If you're sure that the butt end of the yoke bottomed out, you can cut it off without any problems.

Damn Henry---I think I remember a time when life was simpler and everything fit the first time----don't I??????

Brian,

The last time I made a driveshaft, I cut it off twice, and it was still too short.

Denny---I find that you have a great knowledge of things mechanical, and I put a high value on your insights. Please keep in mind that I play at hotrods for fun, but it has never been my career. Really, I'm not sure exactly whats going on with the yokes. I like the idea of pushing a weld rod up the tailstock to probe for a restriction, and I think there is good credibility to your theory of a twisted spline. If I do pull the driveshaft, I will try the other yoke and see how far it will go in. I cleaned the outside of the yoke thats on the driveshaft, but I never looked at the inside of it before I assembled it. Maybe its a twisted spline, maybe its packed full of rust and grunge. I certainly wouldn't want you to pull your post!!!!!!

Originally posted by Henry Rifle
Brian,

The last time I made a driveshaft, I cut it off twice, and it was still too short.

What did you do the day after yesterday?

Denny,

I got over the "vacuum wars" a long time ago. I'm cool if you are. . . not that I won't argue with you from time to time . . .

Oh - and I just cut my reply because I was trying to get out what you and Richard were saying, but I lost my way somewhere in the middle.

Hats off to Denny---Denny, your theory of an internal twist in the spline that is inside the yoke seems to have been right on. I "borrowed" a replacement yoke from the transmission repair shop (don't wanna say begged here) and it slid into the transmission tailstock all the way, just as I thought it should. This morning I bought and installed a new front universal joint, using my already shortened driveshaft and the "borrowed" yoke, and the driveshaft went in with no problems or space issues. I tried to look up inside the bad yoke with my trouble light, and confirmed that the spline is cut full depth, so the only answer can be a slight "oink" in the internal spline that is not large enough to be visible but is large enough to prevent the yoke from sliding all the way into the tranny tailstock.

Originally posted by brianrupnow
One of those unwritten rules that I have kind of "always known" is that when building a driveshaft, have full weight on vehicle suspension, slide front yoke into tailstock untill 1'' between rear of tailstock and shoulder on yoke, and make that the basis for driveshaft measuring. I did that on my current roadster pickup project, (even made driveshaft 1/8" less than I measured). Tonight when I went to reassemble things, the yoke didn't want to slide in past that 1". It's a good thing that I actually went 1/8" less, or I wouldn't have got the driveshaft to go in.-----Now I'm curious---did somebody change the rules while I wasn't looking, or is it possible that since its an old transmission, the splines have worn to a "set" because it went a zillion miles with that same universal at that particular amount of insertion.---On a new turbo 350 will that front yoke slide in untill the shoulder hits the tailstock, or am I smokin something?

is the trans out put shaft protruding pass the oil seal, if it is thats as far as yoke will go. if the out put shaft is up inside the tail housing then it should go all the way untill the shoulder hits the tailstock. the splines should go to the bottom of the yoke.

ps- could be grease or air keeping it from going in all of the way.