If your tight clearance issue is pointing to the smaller diam shaft and stoke u-joint at the pinion end, then I might lean towards machining the slip yoke to fit the smaller diameter shaft. Is there any way to modify, or bush the other pinion end to accept the u-joint that matches the pinion yoke? Do you have a driveshaft that can be shortened?

I don't get it.  the slip yoke is connected to the drive line by a u-joint.  so use the correct sized drive line and u-joints for a 63 galaxie and then a conversion u-joint to connect your slip yoke to the drive line. or am I missing somthing?? My Galaxie has a heaver 9" than was stock and so I had to use a 1310 to 1330 u-joint conversion to mate my OEM(ish) drive line to the wider yoke of my diffeential.

Adding a thicker wall adds little to the strength but adding diamiter adds quite a bit.  I had to lengthen the driveline for my 62 by about 5 " when I swapped in the T5.  I used an OEM 3" drive line from a mid 80s grand marquee, it had standard 1310 u-joints, then had it lengthened and balanced for about $150.  (probably get somthing similar from tons of different Ford cars for about $50 at a junk yard) I have had no strength issues with a 3" tube and standard thickness.  

Also the lighter a drive line is the better soooo going 3" with normal wall width (I think 1/8") will be a nice balance between strength and rotating mass.  

I did a little math and a 3" drive line with 1/8" walls will have almost the same weight as a 2.75" drive line with 3/16" walls but you will get a tone more strength out of the 3" drive line.  I know you are concerned about the 3" drive line being bigger but its really only 1/8" bigger in each direction so as long as you have at least 5/8" clerence with a 2.75" driveline 1/2" with a 3" will be fine.

Here is another thought, what is the size and spline count for the tail saft in the transmission?  The reason I ask is when I took the 3 speed out of my 64.5 Mustang and dropped in the 4-speed toploader I was able to use the same slip yoke.  When I upgraded to a mid 80s AOD in my Galaxie I was able to use a slip yoke from a 1965 C4.  Then when I dropped in The T5 in both my Mustang and Galaxie I was again able to use the same slip yokes the only issue was I had to cut off about 1".  My point is, that all these different transmissions use basically the same slip yoke so is there any chance your newer trans will use the older stile yoke??

dan_6776 wrote:

I better explain:
When I went to the driveshaft shop, I was told that my original 61 driveshaft could not be lengthened.

I think your driveline shop is trying to pull a fast one. ANY drive line can be lengthened. Aluminum ones take special equipment but a steel one is a piece of cake. You put the drive line in a lathe cut the welds away and pop the ends out. you then press the original ends into a new longer piece of tubing, square them up, index them identically and weld them up. Then all they have to do is balance the drive line and your good to go.

dan_6776 wrote:

I better explain:
Secondly, they said that I would have to go to a wider diameter driveshaft because the factory diameter of 2 3/4 inches would not support 5 more inches of length, it would not have enough strength.

I'm not buying that either. 5 more inches of length is not going to take a drive line from adequate to inadequate. Yes it won't be quiet as strong as the OEM length but should still be more than ample. If this was a drag car or something like that than that 5 extra inches would be an issue but IMHO not in your case.

dan_6776 wrote:

I better explain:
By following there recommendation i came to the conclusion that I needed to go to a wider diameter driveshaft of 3 inches.

My recommendation find a different driveline shop. Now with that said a 3" inch shaft should fit fine. I would find a junk yard 3" unit and have it lengthened.

dan_6776 wrote:

I better explain:
By doing so, the slip yoke needed for the 4r70w would fit into a 3 inch diameter driveshaft but the pinion yoke for the 61 was designed to slide into a 2 3/4 diameter driveshaft not a 3 inch tube. I just assumed there was too much play and that is where the confusion started for me.

Like I said before drive line size has nothing to do with slip yoke size or pinion size. What needs to match is u-joint size or use a conversion u-joint. I have a driveline in my garage that I took from a 72 wagon, its a 4" driveline but it takes a 1310 u-joint just like the 2.75" drive lines that came on these old cars. I just did an internet search and the the stock slip yoke for a 4r70w is different than the older ford slip yokes so your OEM yoke won't fit, BUT it takes a 1330 u-joint so all you need to do is find a 3" driveline at a junk yard that takes either a 1330 u-joint or a 1310 u-joint, have it lengthened and then use a 1330 to 1310 conversion u-joint at which ever end doesn't match. In other words if the donor drive line uses 1310 u-joints than you will put the conversion u-joint at the slip yoke end if the drive line uses 1330 u-joints than put the conversion at the pinion end. Here is a picture of a conversion u-joint as you can see it is taller than it is wider. The way it is standing in the picture it is 1330 vertically and 1310 horizontally

dan_6776 wrote:

I better explain: I figured the pinion yoke needed to fit snug in the driveshaft for welding.

Any competent drive line shop does all welding on the bench not in the car.

dan_6776 wrote:

I better explain:
Also, I don't know how much clearance I need for the driveshaft to deal with suspension travel and any driveshaft deflection. I assumed I needed to stick to the factory diameter of 2 3/4 inches to avoid issues.

Like I said before going 1/4" bigger in diameter will only decrease the clearance between the driveline and the underside of the car by half that or 1/8" I am sure you will be more than fine, especially if the suspension is any good. My 62 has a 3" drive line and there are no clerence issues, in fact its not even close

Now with all that said the $900 your drive line shop quoted you is flat out over priced. you can get an aluminum driveline custom made for your application for less then $500.00 I did a google search for "custom aluminum drivelines" and this was the first link that came up. I am sure there are lots of other places to get them as well. An aluminum drive line is far superior to steel because of less rotating mass. Not saying go aluminum, just saying that if you can get a far superior drive line for $500 why have an inferior one made for $900.

http://www.iedls.com/Driveshafts/Custom-Aluminum-Driveshafts.asp

A good driveline shop should be able to lengthen a junk yard driveline for less than $300 and a junk yard should be able to sell you what you need for less than $50. Who knows if you go to the junk yard with a tape measure there is always a chance you can find exactly what you need with out having to have any modifications made.

dan_6776 wrote:

I'm sorry for dragging this on...I just want to get this to work the easiest way. I think I got some bad information at the driveline shop and it really messed me up. Just not enough experience with this stuff to figure out on my own. I appreciate the time you are spending on this for me.

Dont apologize, that is why we are here I am happy to help.  Besides in a forum situation like this we are not just helping you but anyone else that has drivline questions in the future.

dan_6776 wrote:

Ok, first order of business find another driveline shop!

I couldn't agree more!!  Second order of business, give the new shop enpough info to help you but not so much that they see $$.  Let me illustrate with a story.  When I first started my restoration projects I called a local junk yard and said  "I need an oil pan for a 1965 ford Mustang with 289"  There reply was, "yes we have that $150"  I was then told by a friend never tell them that you are restoring a classic car because they here the work classic or Mustang and the price goes up, so about a month later I called back and said,  "I need an oil pan for a 1977 Ford Granada with 302"  (Exact same oil pan as the one I requested for a Mustang) There reply was, "yes we have that $50"  It is unfortunate that peopel are like that but I have found it to be very true of junk yards and automotive machine shops.

dan_6776 wrote:

is 1/8" less outside diameter. I can slide it onto the 4r70w tailshaft but the seal won't seal. Not sure if I could get another seal to work? The OEM slip yoke has 28 splines the 4r70w has 27 splines and a gap where there should be a 28th spline.  

That is exactly what I found when I researched you slip yoke.  You can not use the smaller yoke because its not just the seal there is also a sleve inside the tailshaft of the transmission that helps center the slip yoke.

dan_6776 wrote:

Shot of the driveshaft exiting the tunnel of the frame cross bracing. Looks like going to a 3 inch drive shaft shoud work.

I too think you will have more than enough room.  This car is a virt??

dan_6776 wrote:

The top driveshaft is OEM. The bottom driveshaft is for the 4r70w. You can see how it tapers down to 3" OD. If I understand correctly, get that slip yoke removed and then welded onto the 3" donor driveshaft. If so, I need to find a 3" driveshaft long enough to shorten or get some length added.

Nope this project just got a whole bunch easier.  I did not realize you had the 4r70w donor driveline.  All you need to do is have it lengthoned using a new piece of DOM tubing that is 3" the full length.

Driveline 101:  a driveline is typically made of 6 pieces:

1 tube
2 u-joints
2 driveline end yokes
1 slip yoke

The tube and u-joints are self explanitory.  The driveline end yokes are what go on either end of the tube and look like the following.

The end yokes press into the tube and are then welded in place.  The u-joints can then be installed and the front u-joint connects to both the slip yoke and the end yoke. 

You have everything you need except a long piece of 3" DOM tubing.  What you need to do is take the larger driveline to a new machine shop.  have them cut off the old 4" tube and replace it with a 3" tube that is long enough for your application.  Piece of cake no need to go looking for a junk yard drive line because you already have everything you need.

dan_6776 wrote:

Lastly, get a conversion u joint to mate the donor 3" pinion yoke on the driveshaft to the OEM pinion flange?

Yes and no.  you are correct that a conversion u-joint should be all that is needed to mate up the freshly built driveline to the rear diff, BUT you can't refer to it as a 3" or a 2.75" u-joint or slip yoke  it will create confushion.  Perfect example your donor driveline looks to be a 4" driveline but has 3" flanges.  U-joint size is what you need to refer to things by.  When I researched  the slip yoke for your transmission the lisiting I found said the u-joint was a 1330, however  If I were you I would confirm the u-joint size on the donor driveline before doing anything else.  What year make and modle did it come from??  with that info I can find out the u-joint size.  Your OEM Galaxie u-joints should be 1310.