Balancing a two-piece driveshaft
 

I was just reading another thread about removing a two-piece driveshaft, and another member mentions marking the shaft before disassembly, because they’re balanced from the factory.
I’ve had mine apart 3-4 times to replace the carrier bearing, and didn’t know about this detail.
Is there a way to line up the two halves to get the DS back in balance?
Just curious

Re: Balancing a two-piece driveshaft
 

Not really. Best bet is to take (or send) to a drive shaft specialist and have them balance and "re-phase" it for you. At this point, I would be tempted to install a single piece shaft. Unless you have found a source for support bearings that last more than a year or two. That is my plan to complete my LS swap.

Re: Balancing a two-piece driveshaft
 

That was me. If you don't notice a driveshaft vibration, I wouldn't worry about it too much. I didn't intend for my note to cause any stress. I think a lot of our trucks have been apart many times for the carrier bearings over the years before most of us owned them (as the poster above commented, they do need frequent replacement). I think it's probably a bit more important to pay attention when you remove the u-joints and reassemble.

Re: Balancing a two-piece driveshaft
 

I just dissembled a two piece drive shaft from a 1970. It could only be indexed one way at the slip yolk.
There is actually two reasons that the drive-line need to be indexed.
1) The balance.
2) The U-joint phasing.

Of the two, phasing is the most important.

https://www.youtube.com/watch?v=dt69zYAcXME

Re: Balancing a two-piece driveshaft
 

I posted in another, much older post, where the OP was explaining the same noise/vibration I am getting ~40 MPH. Its on my list to have looked at and found the right shop to have this done here local to me.

Though, what are the pros-cons of going from two-piece to a one piece drive shaft? Why isn't it factory one piece to begin with - I mean I assume there is a reason to have a two?

I am a LWB...

Re: Balancing a two-piece driveshaft
 

It is not always clear why the OEM's go with a one or two piece driveline as the engineering is interpretive. And cost is always an issue.
In general terms, a two piece is used when extra length is required.
Or when the vehicle cross-members do not allow large diameter drivelines.

The simple explanation is drivelines tend to whip at higher speeds.
To combat this tendency they get bigger in diameter as they get longer.
This is the reason front drive-lines are much smaller in diameter as it has little to do with load capacity.

Phasing of the driveshaft is done when the driveshaft is welded up. If yours isn't marked from the factory and it can be assembled in as many different different locations as it has splines all is not lost.
The The U-joint phasing dictates the driveline go together in one of two ways. Set the phasing correctly and drive it. They rotate it 180 degrees and drive it again.
If it affects the truck you will likely know which is correct. In general. if your issue is caused by the driveline balance it would have to be a mile out of balance to impart the energy to the truck you are concerned with.

Balance is always at the rotating speed of the mechanical part. Drive-line will cause a vibration issue at 3.7 times the rotation speed of the tires. (If your axle ratio is 3;70) Maybe you can tell the difference by feel? I would also put the vehicle in neutral and coast at that 40mph. It's possible the vibration will go away. If it does it's in the motor.
Including moving the tires from the front to the rear. Jack up the rear and observe the tires as they rotate. Sometimes you can see a bump that isn't visible otherwise.
Eliminate as many issues as possible. One can learn a lot this way.
Hope this helps.
Rick

Re: Balancing a two-piece driveshaft
 

If it is the motor causing this at ~40 MPH - what in the motor would cause it. I'd image not something easily fixed, as if it is in the drive shafts...

I'll do that neutral test the next chance I get!

Seem my truck will take a bit longer to get back. The shop guy forgot to factor in the time to get the front end aligned (different shop) and they appear to be having issues getting the old brake lines off. Which I was pretty sure the guy would want to replace them, rather than just hang up the rotors on a wire. Which is why I included all new rubber brake lines (the two fronts and the one in the rear too) with all my Moog parts. I am actually happy they are replacing them, I figured they might be a bear to get off and they looked to me like "maypops"!

Re: Balancing a two-piece driveshaft
 

I never eliminate anything with out evidence.
A incorrect flex plate could be a source of motor unbalance.

Re: Balancing a two-piece driveshaft
 

It would be a bit of a drive for you.

Here is a link below to (The Best) driveshaft guy around:metal:

Drive shaft Dave.

Link: https://www.bing.com/maps?&ty=18&q=D...45613&v=2&sV=1












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Re: Balancing a two-piece driveshaft
 

Custom Iron in Newport can balance it for you. Hes on Warford Road.
423 623 3802

Re: Balancing a two-piece driveshaft
 

Thanks! When I get to it I’ll go talk to him.:metal:

Re: Balancing a two-piece driveshaft
 

You can play with driveshaft balance by using a worm screw hose clamp. The worm screw will act as a balancing weight that can placed in any position desired. Clamp it on near the carrier bearing, go for test drive. Keep moving the location of the worm screw until the vibration improves or changes. This will tell you a lot.

Re: Balancing a two-piece driveshaft
 

not sure its the driveshaft, it stops making that noise when I slap it in neural (but it also stopped when I let off the gas too).

Re: Balancing a two-piece driveshaft
 

Jack the rear wheels off the ground and run the vehicle stationary. You can isolate a midrib of issues this way.

The information so far indicates a differential issue. Have you Checked the oil in it? The stationary vehicle test my help point to or eliminate any differential issues.
Have someone drive and someone outside to watch and listen while the vehicle is jacked up. Find a parking lot where you can drive in a circle with someone standing in the center of the circle.
These are simple tests that help identify a lot if issues.

Re: Balancing a two-piece driveshaft
 

.
Here's a thread from yesterday
With interesting food for thought:chevy:


Thread Link:http://67-72chevytrucks.com/vboard/s...shaft+velocity

Video link: https://youtu.be/gmV4qwLfOMY

As always comments are Funny:lol:










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Re: Balancing a two-piece driveshaft
 

Well, it isn't the drive shaft or any of its bits or the rear end. I had it on the rack yesterday and everything is in perfect order. The rear end cover was removed and all checked out - other than the oil needing a well deserved change (the report was it looked like swamp mud). The shop said the rear end bits are in such good shape, that they were pretty sure it couldn't have been original 72 internals. Though I haven't any information any work has ever been done on it but that doesn't mean it hasn't been worked on prior to me getting the truck!

They did find one of the rear wheels being out of balance real bad, which kind of pisses me off as the tires were replaced about two months ago by Discount Tire.

So the good news, rear end is in great shape and I no longer need to worry about the minor cover leak, the state of the oil, drive shaft, or U-Joints/Carrier Bearing.

Bad News, no improvement in the ~40mph noise. So that means it is coming from forward of the drive shaft or I guess the engine / flex plate??

Re: Balancing a two-piece driveshaft
 

Not surprised about the out of balance wheel. I've had major problems with Discount Tire/Americas Tire and balancing. Numerous locations here in SoCal. What is the noise at ~40 mph? Bearing or whine from the tires. I have a slight noise at the same speed that was getting worse. Swapped out front and rear bearings check everything out and couldn't figure it out. Rotated tires around and the noise changed.

Re: Balancing a two-piece driveshaft
 

like a harmonic distortion / hum and only when I am maintaining speed at ~40. I can speed through it or let off the pedal and it goes away.

Re: Balancing a two-piece driveshaft
 

I got fed up with the high prices and poor workmanship from local tire places balancing and mounting my tires, plus the waiting game.

I mount and balance all my own tires now with nothing but a Harbor Freight tire changer, a tire iron, and a HF bubble balancer. There is a bit of a learning curve to do it, but watch youtube for the tips and tricks.

Re: Balancing a two-piece driveshaft
 

I tend to agree but I am not so clever I think.

My 1st problem I had after getting my tires done as I was driving in Austin and being a nice day that day we had our windows down and A/C off. I heard this god awful clinking sound that seemed to start to come from everywhere. I pulled over into a parking lot and found that I almost lost one of my center caps (I have rallies). I had already lost one screw and the other two were just a 1/2 turn from falling off. I was all kinds of upset. Luckily I had one spare matching screw at home (but a bit rusty). If I hadn't decided to go get lunch with my son and stayed on the highway instead, I am sure I would have lost that cap.