To balance or not.... driveshaft

[50mech]

So my off topic Ford van broke the ears off the rear u joint on the driveshaft.

The local pull a part had destroyed every one they had by forklifting the vehicles.

A full service yard that thought they had one ended up not having it after waiting a day for it to get pulled. I didn't want to wait 5 days to get a new one.

 

Anyway I took the end of one from a 97 f150 that had the proper end to bolt on my rear end, cut it and spliced it to my old one with a six inch section I reduced the diameter on to make an inner sleeve.

Welded each end to the sleeve, then welded together the welds, then made a cover pass over the whole thing.

 

It's rock solid with no noticeable vibration to 65mph ( I don't really ever drive it faster than that)

 

Question is....should I still throw in a quart of oil to make it self balancing or am I good since there's no vibration I can detect?

Edited August 27, 2020 by 50mech

[plymouthcranbrook]

I personally would just drive it unless circumstances changed. Maybe take a look underneath after a few miles to make sure all is tight and no seals are leaking. 

[kencombs]

I made up a temporary shaft years ago when I swapped a Mustang V6 with C4 into my little Dodge D50.  Intended to use it to test drive and debug, then get a real shaft made by a real shop.  Worked so well, I never got around to the better one.  So my answer is obviously, run it 'til there's a good reason not too.

[plymouthcranbrook]

1 hour ago, kencombs said:

I made up a temporary shaft years ago when I swapped a Mustang V6 with C4 into my little Dodge D50.  Intended to use it to test drive and debug, then get a real shaft made by a real shop.  Worked so well, I never got around to the better one.  So my answer is obviously, run it 'til there's a good reason not too.

I had a 79 Plymouth Arrow pickup. The idea of the v6 is something I had never considered. I like it.

[50mech]

I was pretty much in the same school of thought as you guys with this. If I didn't know I did it I'd never notice.

I guess I got lucky....?  

Considered oil filling or field balancing with hose clamps but without noticable vibration the latter couldn't be done anyhow.....I guess I'll leave it be.

 

Just wanted to make sure I wasn't going to get a story back about one that ate rear end input bearings until it got balanced but never vibrated or something.

 

On the plus side, the f150s u joint bearings are about 50 percent larger than the originals and probably closer to what they should be on such a heavy vehicle.

Edited August 28, 2020 by 50mech

[kencombs]

9 hours ago, plymouthcranbrook said:

I had a 79 Plymouth Arrow pickup. The idea of the v6 is something I had never considered. I like it.

Mine was a 79, with the spoke wheels in body color, bright orange/black.  2.6 with the little third swirl valves, and it dropped one of those.  So, I found a mustang that a guy had bought, rebuilt the engine, painted and gave to his daughter.  She drove it less than 1 block from home, pulled into the path of a semi.  No personal damage to her, but the front end of the car was moved about a foot to the right.  Great donor for my project.  Engine, trans, shifter, exhaust parts etc.

[kencombs]

6 hours ago, 50mech said:

I was pretty much in the same school of thought as you guys with this. If I didn't know I did it I'd never notice.

I guess I got lucky....?  

Considered oil filling or field balancing with hose clamps but without noticable vibration the latter couldn't be done anyhow.....I guess I'll leave it be.

 

Just wanted to make sure I wasn't going to get a story back about one that ate rear end input bearings until it got balanced but never vibrated or something.

IMO, bearings/bushings are not often damaged by vibrations that are too small to feel in the car.  But, poor alignment of the slip yoke will kill them quickly.  When I did the first one, I assembled it without welds and installed it.  Then used a dial indicator to align the pieces. The tube and yoke were a snug fit so I could tap them in place  and they stayed put.    Tack welded it in four places then removed and finish welded.  And it didn't warp!!!  I've done others since successfully.

 

6 hours ago, 50mech said:

On the plus side, the f150s u joint bearings are about 50 percent larger than the originals and probably closer to what they should be on such a heavy vehicle.

If I was building a vehicle capable of over, say 4000 driveshaft RPM, I'd probably not do that.  But my flattie will never do that!

[plymouthcranbrook]

3 hours ago, kencombs said:

Mine was a 79, with the spoke wheels in body color, bright orange/black.  2.6 with the little third swirl valves, and it dropped one of those.  So, I found a mustang that a guy had bought, rebuilt the engine, painted and gave to his daughter.  She drove it less than 1 block from home, pulled into the path of a semi.  No personal damage to her, but the front end of the car was moved about a foot to the right.  Great donor for my project.  Engine, trans, shifter, exhaust parts etc.

Mine was similar with a five speed. Bright red, black interior. Traded it on a 302 82 Mustang.  Stupid move on my part.

[50mech]

5 hours ago, kencombs said:

 

If I was building a vehicle capable of over, say 4000 driveshaft RPM, I'd probably not do that.  But my flattie will never do that!

I'd assume if the yoke is crooked it's going to swing the whole driveshaft and cause vibration.

 

In any case I think I lucked out. I couldn't just swap the yoke since the two shafts bottleneck down to different diameters. So my splice is about 8" forward of the rear. 

I just used a 3' straight edge and made my initial  1/2" welds on each pass at 0,180,90,270 before making complete passes. Threw it in the van and off I went, convinced I'd probably need to just order a new one until I hit 65 a few times trouble free.

 

Today is a rare freeway day to go see my lady so I'll get to to hit 70-75 for a couple miles........

Edited August 28, 2020 by 50mech

[50mech]

Well, very small vibration starts at about 72mph....can't even rule out tires as I wouldn't have likely noticed it before so...I'm happy. Just gonna drive her.

With over 360k and being hit by lightning under it's belt I'm not expecting perfection out of it anyhow.

[Frank Elder]

On 8/27/2020 at 1:47 PM, 50mech said:

 

 

Question is....should I still throw in a quart of oil to make it self balancing or am I good since there's no vibration I can detect?

I have never in my life, and I’ve been around a lot of old salts, heard of anybody putting a quart of oil in a driveshaft to make it self balanced.......did I read it wrong or could you explain it to me in a little further detail thank you very much.

[50mech]

10 hours ago, Frank Elder said:

I have never in my life, and I’ve been around a lot of old salts, heard of anybody putting a quart of oil in a driveshaft to make it self balanced.......did I read it wrong or could you explain it to me in a little further detail thank you very much.

Idk. Id guess it more just dampens vibration than really balances. A lot of dirt track racers I grew up around did it.

Not going to do anything for something far out of true though.

 

If you have a minor weight imbalance the fluid in a round tube is going to spin out until it's evenly coating the inside. So if you have this imbalance of say some fraction of an ounce trying to work against this 32 ounce fluid mass that's evenly spread , your fractional ounce is working against quite a bit of force trying to deform the liquid in order to shake. It succeeds only marginally and the throws that normally make an elliptical path formed by an imbalance and tiny amount of play are slowed down and forced to be a bit more round as the fluid seeks to stay in an even distribution within it's rigid round container.

 

If it's further out of true than the spun film thickness or the imbalanced weight is closer to the opposing mass of the spun and deforming film thickness then it just swings the fluid to the most out of true area and makes the imbalance even worse.

Edited September 1, 2020 by 50mech

[Frank Elder]

Thanks for your answer, I guess in the long run I’d rather just make it or have it made correctly the first time than to do something that shouldn’t be needed......it makes sense it would dampen vibration to a certain degree.

 

edit, I wonder what the effect would be on a brand new properly balanced shaft......less chance of vibration in the future?

Edited September 1, 2020 by Frank Elder