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  #1  
Old 08-31-2007, 12:42 PM
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SOA front driveshaft question

Went SOA on my 79 J-10. Ended up with about 6 3/4" of lift.

Ready for the drive shaft.... My original front shaft has the traditional one joint at the front and two joints at the rear bolting to the Qtrac yoke.
Question: Is this a CV joint? So all i need to do is have the original shaft lengthened? This shaft will angle enough for the increased lift?


***edited for clarity
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Last edited by fullsizejohn : 08-31-2007 at 02:21 PM.
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Old 08-31-2007, 01:21 PM
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the two joints (CV joint) should be on the transfer case end. and yeah, you should be able to get it lengthened by a shop.

Al
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Old 08-31-2007, 02:30 PM
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The CV joint is what you are calling the "two joints".

The driveshaft shop is going to tell you that it is much harder to LENGTHEN a driveshaft than it is to shorten it. Keep this in mind before you go over there thinking that they will lengthen it and send you on your way.

You might want to see if you can find a longer driveshaft in the junkyard and then have your CV joint and yoke welded on to it to make the correct length of shaft.
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Old 08-31-2007, 03:11 PM
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ive never had any problems w/ a shop lengthening a shaft. they just have to re-tube it, where as for shortening one they just have to cut out what’s needed.

some people have problems w/ the stock double cardan joint not having enough angularity (is that the right word?) for the lift. might want to make sure its not going to bind before you spend money to get it lengthened.
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Old 08-31-2007, 06:30 PM
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All good comments thanks

So i guess just bolt up the stock "double cardan", hold it down at the approximate angle and see how it turns?

If it is acting like its binding ,i then would want a.........??
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'77 cj-5,
'78 j-10,(not running)
'79 J-10 360ci,t400,D300, SOA-D60w/ARB, 14B w/Detroit,4:56s, 37" TRXUS
'06 Ford F250 super duty crew cab
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  #6  
Old 09-02-2007, 12:13 PM
adamsclarke adamsclarke is offline
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John...your best bet is Standard driveshaft shop down near semmes. just measure you max compression and max extension and they can lengthen it and balance it as well. They are doing my commanod driveshafts this week
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Old 09-02-2007, 12:32 PM
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The "two u-joints" you referred to are also called double cardan, or CV. 1310 u-joints are stock in all driveshaft locations on a Quadratrac equipped rig. Having a driveshaft lengthened costs more than having one shortened, because the entire long tube has to be replaced when lengthening. Shortening just involves cutting the necessary length out of the original tube & rewelding it.

I highly recommend finding a larger diameter/thicker wall tube driveshaft to weld onto your FSJ double cardan. Why? Take a look at this pic - the puney looking driveshaft is the stock FSJ diameter that came on my Chero. Compared to the '80 Chevy K5 front shaft next to it - you can see why I recommend the swap; the puney FSJ shaft bent after some moderate wheeling at Harlan.



I tig welded the FSJ double cardan onto the Chevy front shaft. Chevy shaft = 2" OD, FSJ shaft = 1-1/8" OD. After replacing all 3 u-joints, it is much stronger now.

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Old 09-02-2007, 01:46 PM
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Again thanks guys.

I will head over to Semmes Ave tuesday morning for the work and ,like shepardskeep advises, see if they can go with some heavier tube since its being replaced anyway.

They will need the compression and extension measurements? I was hoping i could just get a resting length yoke to yoke. ????

Adams, pm'ed ya.
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'77 cj-5,
'78 j-10,(not running)
'79 J-10 360ci,t400,D300, SOA-D60w/ARB, 14B w/Detroit,4:56s, 37" TRXUS
'06 Ford F250 super duty crew cab
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  #9  
Old 09-02-2007, 03:30 PM
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Quote:
Originally Posted by jwwdsn
They will need the compression and extension measurements? I was hoping i could just get a resting length yoke to yoke. ????

Driveshaft shops usually need this measurement if they are either making a completely new shaft, or cannot physically look at the application to measure it themselves. I have modified my own driveshafts on several rigs, and wheeled them extensively with no problems. (did I mention that I love to flex? ). You can determine how much longer the shaft needs to be by taking a measurement at ride height, but in order for it to be as accurate as possible you need to know exactly how much slip yoke travel your shaft has (distance that the center of the shaft will compress or extend). Then plan for your main tube to be the appropriate length that allows the slip yoke to be exactly in the middle it's total travel - when sitting at ride height. For example, my stock FSJ front shaft only had 2" total slip yoke travel, so I had to make the tube long enough so that at ride height the shaft was resting with 1" of the slip yoke travel used - and that gave me 1" of compression, 1" of extension. Honestly those are pathetic numbers for a lifted rig that is wheeled hard & stretched like a dollar in Ethiopia. The beauty of my Harlan mishap is that the new Chevy shaft I'm using has 3" of total slip yoke travel, so now I have 1.5" of travel in either direction (from ride height).

If I have to get a driveshaft shop to modify a shaft for me, I prefer to walk in & tell them exactly how long the main tube needs to be - do all the measurements & calculations beforehand to eliminate unnecessary guesswork.
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  #10  
Old 09-02-2007, 03:55 PM
adamsclarke adamsclarke is offline
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yeah...if you didn't do a shackel reversal...yor stock slip is fine...just need to figure out how long. A heavy wall will help..but heavy as in .127 Dom will work..amd .25 for real heavy use..
The heavier the walll...the harder to balance.
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  #11  
Old 09-02-2007, 05:37 PM
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ya go w/ thick wall if'in you plan to have fun.

my shafts are 3" .25 wall.
but then again i can break a steel ball in a rubber room. so i have to over build things just a bit.
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