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Need help for a 720 short drive shaft


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I am new to the this site so I apologize if this is not posted in the right place.  I live in Alaska and need help finding the short drive shaft out of a ‘82 Datsun 720. It is the one that goes between the transmission and the transfer case.  I have am in need of a short one.  I have looked everywhere I can think of online and junk yards but have come up empty.   Since I live in Alaska my options are limited unless I happen to find one sitting in someone’s back yard.  I have a 1985 720 but it has the shorter transmission so the drive shaft is too long.  
 

If anyone can point me in the right direction I would appreciate it.  If anyone has one for sale, please let me know.  
 

 

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Do you have any driveline shops near you? Probably not, but any driveline shop can make it. Maybe source it out to someone in a more populated area. They can walk you through how to measure and count splines, then they build it and ship it to you. Most shops can build a shaft like that for a couple hundred bucks, and yes, I believe all the parts to make that from scratch are available new.

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I’m going to hit young’s gear this morning.  I just don’t know if 1. They will be able to make one, 2. How much it will cost or 3. If they can do it in a timely manner.   Just because they are the only shop in town.  Jones driveline and machine is no longer in service.  Or at least their phone number is no longer in service.   I’ll report back when I talk to Youngs Gear.  
 

thank you

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Well, I guess it boils down to how bad you need it. Can you burn a few days/weeks looking for a used one? Or do you need it right now? $350 is a bit on the high side, but if using all new parts, I could totally justify the cost.

 

There's an old saying - want in one hand and shit in the other one and see which one fills up faster.

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 Are you replacing the shorty with the longer 31.5" transmission from an '82???? If yes then you need the later '83 and up long drive shaft as the flange on the transfer case was also made larger after (I think) about '83.

 

If you actually have an '82 4x4 and need a long drive shaft for it, then only the '80-'82 will work because the transfer case flange is physically smaller.

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Xu5DybA.jpg

 

This is a short primary drive shaft used with the long 31.5" transmissions. Look at the diameter of the tube and the U joints and the flange to the transfer case. The early ones had smaller diameter tubes and flanges. If for a later 720 you'll just want a longer one for use with the shorty transmission. If for the earlier one probably '80-'82, then longer that the one pictured above and smaller U joints, tube diameter and flange. I have put this larger style on by also replacing the companion flange on the transfer case.

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2 hours ago, datzenmike said:

What is it for exactly? and do you have the old one?

They have the old one right now.  But it goes between the transmission and the transfer cast.  The one out of our 85 720 is about twice as long and much thicker.  The actual drive shaft is probably about 4.5 inches long. Maybe 6” if you count the loops for the u-joints.  

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1 hour ago, Stoffregen Motorsports said:

Gotta love the small shops. Saves a bunch of time and usually doesn't break the bank.

$370 seems high for a little drive shaft smaller than my forearm.  This thing looks like it belongs in a side by side only it looks 40 years old.  

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It 'ripped out' because it needed replacing long ago and disintegrated. One or more bearing caps wore and fell out allowing the trunnion to continue to wear the yoke till it failed. 

 

U Joint | Machine Service, Inc.   U joint clips? - Jeep Cherokee Forum

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The U joint has to be worn out first. Once the cap(s) dry out, the needle bearings break and or fall out and the trunnion begins to hammer what's left. At this point it can still be replaced but once through the bearing cap it damages the yoke. When done, try to find a U joint that has a grease fitting.

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Indeed, you might step on the gas harder to move the truck around but if the U joint were proper this wouldn't cause it, just accelerate the wear that was already done. There would have been some vibration and certainly noise.

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They wore out because they are such a paint to get to, so nobody ever did it.

 

Bigger tires certainly can help. Do you know if you are getting the yokes with larger joints?

 

$370 is not a lot, considering the new parts. Sure, a used on can be rebuilt for less than $100, or a stock one modified for $150, but all new everything? Plus tubing and labor. It's right in the ballpark. If it were a Dana Spicer shaft for a Jeep, yes, over the counter for $250, but this is Datsun/Nissan. The land of cheap bastards and little aftermarket support.

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One other thought - does your son use the clutch a lot when he's enjoying those big tires? The biggest mistake I have seen on the trail is guys getting stuck and then revving the motor and riding the clutch. In rock crawling, it's best to give as little throttle input and let the torque get you rolling. Most guys (with manual trans) will even start the truck while in gear. Smooth driving is the best way to save joints and gears. Jerky and lots of throttle, not so much.

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2wd  are not the best for crawling. Additionally worse with larger diameter tires. You can get much wider deep lug tires in the same stock height but it will lower the ground clearance to stock height as well. Better crawl and claw at low speed. Put my '78 620 on an '82 2wd frame and grafted a transfer case in. Ran 33" X 12.5 tires.

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