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Discussion Starter · #1 ·
OK, here goes a driveshaft story. A friend gave me his YJ and as a separate gift I received a front drive shaft. As the story goes he drove over a big rock at high speed with front driver side and the rock cracked differential case. He replaced diff. but nether bothered to put front drive shaft back on. I had it sitting out for a while until with approaching winter I have decided to put it on. I got 2 u-joints knocked old ones out and put them in, ohh yeah in the process of banging old ones out I knocked off the balancing weight. I put the drive shaft back on and drove away in 4WD. 4WD was loud- like a propeller with quite a bit of vibration.
My questions are. Is this normal? Could I have messed up the orientation of the drive shaft since I never marked it on the car? Does that balancing nugget matters much at 40mi/hr.? Double checking that grease bearing goes towards front axle and would greasing it help?
Now as I’m typing this and thinking that Transfer Case was cracked may be front drive shaft was bent. Is there a way to check? Also what is that square plug in front axle refill hole, is it just a 3/8-1/2 ratchet?
Thank you for your thoughts from the trenches.
W
 

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Its a good possibility that the driveshaft is bent. Stock front driveshafts on YJ's didnt come balanced from the factory, so if it was a weighted driveshaft then it wasnt a YJ shaft.

If you are talking about the grease fitting, it should be on the side of the u-joint facing the driveshaft instead of the axle.

As far as the slip yoke, that doesnt really matter, but it should be greased.

The square plug in the fill hole is a standard 3/8 ratchet.
 

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Yes, the square drive plug is the fill plug. Yes, it is just a 3/8ths ratchet.

Any time you get a driveshaft from another vehicle, damaged or not, you should have it balanced first. The balancing weight that fell off is more than enough to cause vibration at any speed. Get the driveline to a driveline or machine shop and have it checked out.
 

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Discussion Starter · #4 ·
If you are talking about the grease fitting, it should be on the side of the u-joint facing the driveshaft instead of the axle.

QUOTE]

I'm talking about grease fitting on the shaft itself, I think that part is called drive shaft oil seal. Where smaller OD shaft goes into larger OD shaft. Now I have it connected with larger OD going into transfer case. I believe u-joints don't come with grease fittings anymore.
 

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Discussion Starter · #5 ·
Yes, the square drive plug is the fill plug. Yes, it is just a 3/8ths ratchet.

Any time you get a driveshaft from another vehicle, damaged or not, you should have it balanced first. The balancing weight that fell off is more than enough to cause vibration at any speed. Get the driveline to a driveline or machine shop and have it checked out.
Is balancing it going to tell me if it's bent or not? What places usually do balancing? Do I need to have u-joints out prior to bringing it in?
 

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I'm talking about grease fitting on the shaft itself, I think that part is called drive shaft oil seal. Where smaller OD shaft goes into larger OD shaft. Now I have it connected with larger OD going into transfer case. I believe u-joints don't come with grease fittings anymore.
[/QUOTE]

That part of the shaft is called the slip yoke. And it is personal preference on which end it is installed on. Some like it up near the t-case, and others suggest it be down by the axle.

And i have never bought after market u-joints that didnt come with a grease fitting.
 

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No, just take the whole shaft assembly to a driveline specific shop, or at the very least a machine shop. They'll be able to tell all that is wrong with it (bent, unbalanced, broken, rusted, etc.) and fix it for you.
 

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<snip> I put the drive shaft back on and drove away in 4WD. 4WD was loud- like a propeller with quite a bit of vibration.
My questions are. Is this normal? Could I have messed up the orientation of the drive shaft since I never marked it on the car? Does that balancing nugget matters much at 40mi/hr.? Double checking that grease bearing goes towards front axle and would greasing it help?<snip>
My opinion, its not the drive shaft causing that. But to be sure we would need to understand exactly where the noise is coming from and all the detail you can think of for the problem.

Does it do the same thing in 4H as 4L?

Is is affected by speed, as in the noise gets worse as you speed up and slow down?

Can you get it rolling then shift into N (transmission) and have the noise change/go away?

Have you jacked it up and engage the 4X and spin the system by hand to see if you can feel where the noise could be generated?

Could you have damaged the uJoints you replaced? I have had the bearings fall and stick to the end causing the ujoint to be offset and grind itself to dust.

In 4X you can feel a vibration if its out of balance; but you shouldnt feel it at first, and it should come on as you gain speed.
 

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Discussion Starter · #9 ·
I guess I got my work cut out for me on the weekend. Glad to know that shaft goes either way front to back or flipped on it’s axis as it was my concern that I installed it wrong. I’ll check the u-joints for needles and make sure there is oil in the axle, and try to follow CAMAROZZ’s check list.
I drove it a bit on a parking lot yesterday 5-10Mi/hr and it seemed OK on vibration but there is a weird muffled sound every time shaft makes a rotation. I turned it by hand and it seemed solid, besides backlash clink when changing direction of rotation there was nothing. Getting into a parking space in 4WD, 1st gear, hard right turn YJ is vibrating like crazy, almost stalling and feels like it’s tripping over it’s own wheels (not the 1st time I noticed that, parks beautiful in 2WD).
 

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hard turns in 4X is normal, you are binding up the system since it has power on it.

Slow mo still has sound and vibration? hmmm

you may be at a point where you need some one to help, but get it up off of all fours, and get it running. Looking underneath for any indication of an issue.

Really, the only difference between 2X and 4X is the axle/diff activation, the driveline, and the transfer case. And assuming the problem is not amplified because of the 4X system, then it almost has to be one of those three. You could take the driveshaft out and try and verify if it is bent, just in case.
 

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Discussion Starter · #11 ·
hard turns in 4X is normal, you are binding up the system since it has power on it.

Slow mo still has sound and vibration? hmmm

you may be at a point where you need some one to help, but get it up off of all fours, and get it running. Looking underneath for any indication of an issue.

Really, the only difference between 2X and 4X is the axle/diff activation, the driveline, and the transfer case. And assuming the problem is not amplified because of the 4X system, then it almost has to be one of those three. You could take the driveshaft out and try and verify if it is bent, just in case.
Let me amend my 1st post a little. Cancel vibration because I don’t think I feel it. It’s more like a magnifying sound with acceleration to the point that I feel that something will fly off, I think brain interprets that as vibration. If to relate it to a scheme from the movie it’s when someone is a duct system and the fan starts turning, first it’s long “ummm” “ummm” and then as fan accelerated “Um’s” become shorter and blend together (closest I can come to describing it). Now that I think of it, I definitely need to check oil in the axle, I don’t know if anyone ever used it, checked it or changed it. If there nothing “swooshing”, lubricating, damping in there it could be the reason for building up “Um’s” with RPMs. When I was out ther I wasn’t smart enough to figure that filler whole is just for a 3/8” ratchet, tried my star sockets, looked around in a tool box scratched my head and could figure out what fits it.
 

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:) Been there...

seems to me you are describing a bearing "um"; you say this only happens in 4X?

If so, you could be looking at carrier/yoke bearings, or even bearings in the transfercase I suppose.
 

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Discussion Starter · #13 ·
:) Been there...

seems to me you are describing a bearing "um"; you say this only happens in 4X?

If so, you could be looking at carrier/yoke bearings, or even bearings in the transfercase I suppose.
Definitely only 4X. Just drained and topped off transfer case, I guess I can run it in 4X without the shaft and see if it “hum”s but it could be deceiving since it’ll have no load. My money is on front axle oil as far as I know it’s dry or full of water, got everything ready for it RTV, thread locker, 2 quarts of 75W90.
 

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Discussion Starter · #14 ·
Actually not "as far as I know it’s dry or full of water" I meant to say "I don't know it coulb be dry or full of water"
 

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Definitely only 4X. Just drained and topped off transfer case, I guess I can run it in 4X without the shaft and see if it “hum”s but it could be deceiving since it’ll have no load. My money is on front axle oil as far as I know it’s dry or full of water, got everything ready for it RTV, thread locker, 2 quarts of 75W90.
Whats the thread locker for?

RTV and the oil is all you should really need.
 

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Yeah, locker would be overkill, the RTV will get on the threads and do the same thing.
 

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Discussion Starter · #18 ·
Front axle oil changed. I think it’s running better. I get a wind down sound once I come to a stop and I drop it in neutral. Is that normal? I might have the same sound getting up to speed but between engine and exhaust noise I can not hear anything. Well first snow is falling time for 4WD test. I wish I had better tires.
 
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