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FNG with a drive shaft question


barnett3006

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Hello.

Ol' blue is a '91 4x4 xlt extended cab with the 4.0, M50D, push button transfer case and is otherwise stock except for heavy duty springs that I swapped in the rear a few years ago when a had to tow more then the old, sprung factory springs would let me. Don't remember what vehicle they came from, an explorer maybe, but they went right in and gave a a few inches of lift in the rear.

It is now time for me to replace the carrier bearing for the 8th friggin time :annoyed: and after doing some research during a clutch replacement I recently finished I stumbled across the 98 drive shaft swap totorial here at TRS. I have been unable to find the right drive shaft locally and I'm not going to pay LKQ prices for one, so the next best thing for me is to roll my own. I got another shaft with the correct ends and a length of driveline tubing.

My question is, is the weld to weld length of 47" a "good enough" length and is there an optimum length? My drive line tube is 48" long and wanted some opinions before I cut that inch off. I ask this because my time for this kind of stuff is short and this truck is my daily driver so I need to have the new shaft ready to go for when I have time to get that damn 2 piece shaft out. Otherwise I would pull the shafts out and make some good measurements to make the new shaft to.

BTW, this forum has been an invaluable resource to me over the years, I just never had a need to register and post anything until now as the info I needed had already been addressed, I couldn't find the answer to this however.

Thanks in advance,
Marc
 


Shran

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This is the way I make driveshafts:

Measure center of u-joint cap to center of u-joint cap from t-case to axle. This is your rough length at ride height. Call it "Measurement A"

Then figure out your slip yoke travel, from fully compressed to fully extended. Usually around 3" total travel or so. Find the halfway point of that, and measure from the center of the u-joint on that end to the point where it's welded onto the tube. "Measurement B." Adjust your tube length so that the tube plus the weld on flanges plus the Measurement B equals Measurement A.

Doing that will result in a driveshaft that has a slip yoke that's set roughly in the middle of its travel with the suspension at ride height.

Next, you want the ears on the yokes aligned with each other as close as possible along the length of the tube. You can get it close, put the shaft on the floor so that the ears on one side are flat against the floor, and rotate one yoke so they're lined up. Now flip the shaft over and check the other ears. It helps to measure off the floor sometimes - you want the tube to be the same distance off the floor on both ends as well, this way the shaft is straight.

You can tack weld the yokes on at this point with ONE tack per yoke. Carefully install the shaft into the vehicle. You need a dial indicator on one end of the shaft, and you will rotate the shaft and adjust for runout. Then check the other end, tack weld a few more times once you get it as close to zero runout as possible. Remove from vehicle and fully weld.

Done!

Note that this is a very imperfect way to do driveshafts. They WILL vibrate at least a little, they will not be balanced, but I have done this many times for trail rigs and it works great. Both driveshafts in my rock crawler were made this way out of 1/4" wall poop pipe.

For a reliable daily driver, it's best to take it to a driveshaft shop where they can get it 100% straight, square, and balanced.
 

barnett3006

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Thanks for the reply.

It looks as if I'm not going to get out of taking the 2 piece DS out before I'm ready to put the new one in, lol. Your method of measuring sounds pretty good and I will be using that.

Just for clarity, fully extending the slip yoke is separating the halves or is there a minimum contact length? 1" or so? Same for fully collapsed, should there be .5 or .25 of an inch of cushion before the ends hit? Differences here will move the "center" of the slip yoke.

Getting the new shaft straight and square shouldn't be an issue, and there is a guy local that can balance it for me.

Thanks again,
Marc
 

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I would leave at least an inch of contact in the slip yoke at your longest point and measure at fully collapsed for the shortest. Seems like I usually end up with about 2.5" to 3" total travel with Ranger driveshafts.
 

barnett3006

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Great! Thanks!

Hopefully I have time this weekend.
 

barnett3006

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So an update, that would've come sooner except I had to go out of town for 3 weeks, with a problem and some more questions.

I got my new driveshaft welded up and put together with new u-joints and was ready to have it balanced when I found out that the guy local to me cannot, in fact, balance​ a driveshaft.

The carrier bearing on the two-piece shaft is getting noticably worse everyday, so I am now interested in the centrifugal/liquid method of balancing my new drive shaft.

How well will this work for a DD that mostly sees city/highway speeds with the occasional trip up the interstate?

Where is the best place to drill the hole for the pipe plug? I will be using a 1/4" brass plug.

Is anti-freeze the best liquid to use or would a thin oil like ATF be better?

And how much liquid should I start out with? I've read of people using this method but the measurements are always a roundabout "couple cups". And depending on where the plug is I can see adding more OR draining it would be easy, but not both.

Thanks again in advance,
Marc
 

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Most driveline shops will refuse to balance shafts that customers build... pretty standard procedure. They have no way of knowing if the shaft is straight and true since they didn't build it.

I don't know about the liquid thing, keep in mind the pipe plug will act as a weight and throw the balance off further... best bet there would be to drill a hole, fill, and weld shut. In that case I'd use sand or something non flammable. Not a clue how much to use, keep in mind that it's all going to stay at the low end so if the shaft is off at the high end, it won't balance anyway or could be worse.

My suggestion would be to find some strong magnets and attach them to one end of the shaft with zip ties, then you can play with the magnet's position or move it to the other end of the shaft. Once you find a spot with minimal vibration, permanently attach it.
 

barnett3006

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Hmmm, well. I geuss I will use the hose clamp method until I can get it to a shop that'll balance it for me.

I will let y'all know how it goes.
 

barnett3006

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Great news! I got the old 2 piece DS out, my new home built DS installed and test drive it working my way up to 65 with only a minor vibration around 55 with no balancing tricks done! It is leaps and bounds better then with the loose, crappy carrier bearing flopping around. I put a hose clamp on the transfer case end and marked the shaft to index the lug to try and smooth out that minor vibration further on my way to work tomorrow.

I wish I had learned of the 1 piece DS swap years ago!

Here is a pic of the old vs. new
IMG_20170531_185046194.jpg

The ends came out of a Ford explorer, the drive line tube is a recycled DS from a 78 Malibu (of all things, LOL, it was the right length, diameter and wall thickness) and 2 brand new u-joints.

Thanks for the help and advice!
Marc
 
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Shran

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Good work. Mine vibrates a little at highway speeds, but I'm not sure how much is even driveshaft related. Probably some but there's always at least a couple things that vibrate in a lifted truck. I live with it.

Hose clamp will work better than magnets.
 

barnett3006

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Well it seems that there isn't a happy place for the hose clamps to be so I'm just going to live with that minor vibration. No big deal I suppose, the truck is old and it might not even be coming from the new DS, could be from somewhere else thatI couldn't feel with the old 2-piece DS flopping around. I am due to make a run up the interstate soon so I will see if it's any worse or not at 70-75.

Thanks,
Marc
 

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