HYRYSC

I gotcha and appreciate your responses. I checked on the things you suggested but I had already ordered the new front driveshaft anyway because I wanted matching front and rear driveshaft anyway.

I am going to call the shop that did the work (they came highly recommended and every 4x4 shop in my area said that they used them for any diff/transfer case/tranny work that they had) and see what their thoughts are.

Jeep Driver

Yeah, please let us know.


BTW, there is nothing like a REAL DS............as you will find out.

Fred/N0AZZ

I'm interested in what the shop says also I would think that they would have test drove it before delivery. I'm at the same lift height with 4.56 gears and like you have a new rear custom shaft with a stock front one. No issues at all with mine in any way, when I first test drove it from there shop after all the work had a shimmy in the front took it back and they fixed it in about 25 min.


See if they can't find the problem with the drive shaft you sent in with it that was working properly before. As any new DS should be in perfect shape find the problem with the old one.

Jeepin'_Aint_EZ

IDK I haven't had any problems running stock front shafts (front and rear) in my rig. Maybe one day I'll drop money on a "real" shaft so-to-speak lol

Boostwerks.com

I can't believe no one has mentioned this... but a lot of people will have this problem after a re-gearing to a higher ratio. This is simply because the driveshaft is now spinning substantially faster for any given speed. You may have had a vibration at 80, and now notice it at 50 for example. Any little variable such as an unbalance, pinion angle, worn joints...etc, will all be amplified by the gear change.

I hope the new shaft works out for you, but don't be surprised if you still have some slight vibes left over. If so, the pinion angle is more than likely the culprit.

TRCM

I didn't specifically mention that, but what I was trying to get at was the changes from the new stuff have to be the cause....just got to figure out what it is and decide if fixing it or new parts is better.

Going from 3.55 to 4.88 is a 37% increase in drive shaft rpm...so it could well be something that was not noticed before, but now it is.

Have you corrected your speedometer yet ?? If you had a drive-line vibe @ 68-70 mph before, it will show up now as 49-51 mph on an uncorrected speedo.

TRCM

Not even close to what he said.

"a lot" is not everyone.

And he said the OP may have had a vibe before that didn't show up as noticeable that now IS due to the increased driveshaft rpm.

Just like how your tires can seem to be balanced fine, till you get up over 80, then they don't. It's due to the increased rpm.

Or how you tcase whines more in low range than high......higher rpm again.

If you want to get technical, a change to anything in the driveline, specifically one that increases rpm, you should expect to get a vibration, especially on vehicles as old as ours are.

HYRYSC

That is a great point about the shafts spinning faster. I did not rebuild the driveshaft because I knew that I was getting another one but normally I would have. The vibes are not that bad, more of an annoying sound that feel.

However I might have noticed something else. I bought a set of Iron Rock pinions front and rear because I was upgrading to u bolt design and wanted new ones anyway. Well today I was out under the jeep doing some wiring for my upcoming Viair system and noticed a decent burr sticking up on the side of the front pinion. Probably not enough to cause much of an issue, but I am sure it wasn't helping. I will file it smooth tomorrow and give another high speed test run.

I was reading on another forum about a guy who regeared a truck and experienced something similar until the gears were broken in. Who knows but whatever it is, I will eventually keep trying stuff that you guys are recommending and will get it fixed.

I can tell you guys one thing; the new lockers with 4.88 gears completely ROCK! I put it in low gear/low range today with the front locked and literally I could get out and walk beside it as I idled across my property! I am in love!

Fred/N0AZZ

Liked we spoke of earlier my gears/lockers were single best improvement made on my XJ for off road use and on road with the tire size/mpg's gained.

TRCM

The point I made with the letters you bolded.......it's not just the driveshaft....EVERYTHING is old !

Heck, for all he knows, the housing is whacked and the old gears didn't show it cuz they were worn to match, but the new ones aren't.


And what is this balanced @ 1000 rpm, and then balanced @ 2000 rpm ?

If it's balanced @ 2000, it will be balanced @ 1000. At least on the motors & equipment I have watched get balanced in the past, if they balanced @ 3600 rpm, they were balanced @ any rpm below that just as good.


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TRCM

Well, I'm no child, but I have come to learn you are convinced of your own superiority....too bad no one else is.

And your 11 year old homeschooled son reads above the high school level...big deal...so did my public school taught daughter when she was 8 (not really saying much these days tho). I guess your saying he is homeschooled is just another attempt by you to try and tell us how smart you are.

Back to the issue:

1) Just remember genius, in his situation, the driveshaft isn't the only thing that is spinning.

2) In your previous post, what you said was incorrect. Here, I'll quote it for you:
.

There....the bolded statement is wrong.....a rotating mass (shaft, motor, etc), can be balanced at 1000 rpm, but be out of balance at 2000 rpm, since the forces that make it out of balance grow exponentially as the rpm goes up.

It is also grammatically wrong....and should read "A shaft........." not "As shaft", and the rest of the statement is up for interpretation as to grammar.

3) Your statement in the current quote that is bolded is also wrong. Ideally, it would be true, but it would have to be perfect. I use to QA (that's quality assurance just in case) balancing electrical motors and rotating equipment in the military, and I can tell you for a fact, that you can have a motor balance out 0.00000 @ lets say 1800 rpm, and then you spin it to a higher rpm, like maybe 3200 or so, and it can be out.

That's why a lot of equipment that is balanced has an rpm limit, because above that rpm, the balance is not assured to still be good.

4) None of us said that because he regeared he should expect a vibration in the driveshaft (altho that is a likely spot), but that he should expect a vibration, as there are many moving & rotating parts that can cause one (most of which are old & worn) , aside from the driveshaft. You seem to have forgotten this fact in your quest to convince everyone that a new driveshaft is the only thing needed.

Everything from the front pinion to the engine will now be running at a much higher RPM for the same speed, and the chance of a vibe from ANY of that is high.

5) And as for 'posting for the benefit of others"....if you say so. Not sure claiming the ONLY thing wrong or that can be wrong is the driveshaft is a benefit.



By the way, how do you know it's the slip joint that's bad, and not the cardan joint ?? or the ujoints ?? oh wait...you don't. You're just guessing...................

.

89eliminator

do you have an SYE? if so, do you use a stock XJ front driveshaft as your rear driveshaft? swap driveshafts to see if the problem moves to the rear.

HYRYSC

I do have an SYE, but have an Adams driveshaft in the rear. I have another one ordered for the front.

TRCM

Jeep Driver.......something to consider......then I'm done.

John (just a generic name) has a vibration coming from the right front area of his jeep. Like a good problem solver, he checked the tire and rim, and there is no obvious damage or problem, plenty of air, no weird tread wear.

Next, he swaps the front tires side to side, to see if the problem moves with the tire, just as any good problem solver would. It doesn't move...he still has the vibration in the same spot.

Now, keep in mind he has had 2 different tires mounted on that corner of his jeep, and he still has the vibration in that corner of his jeep....so, what does he do ??


Ok........using your logic, he now must go buy a new rim & tire and put it on in that corner of his jeep, as that is the only thing that will fix his problem and make the vibration go away.
Forget trying to look and see what else may be causing or contributing to the vibration....like maybe wheel bearings, ball joints, bent axle, bent rotor, sticking caliper.....no, it's not any of those.......only a new rim & tire will fix it.


Silly right ?? Well, it's no different than saying that a new driveshaft is gonna fix his problem and nothing else could be causing or contributing to it. I mean he did try 2 different driveshafts, and still had a vibe. So the chances are good it ain't or ain't just the driveshaft. I never said he couldn't use a new or better driveshaft, but I did say it is likely not the only problem, and he may not need a new one.


That's all I've been saying all along, is since he has a vibe with 2 different D/S's, he needs to check to make sure it isn't something else as well before spending coin on a new one.


And if just a new D/S does fix it for him...I'll say good for him - problem solved, Jeep Driver was right.....but I won't apologize or say I was wrong, because nothing I have said or suggested to help troubleshoot the vibe and what is causing it has been wrong.

Just like the tire scenario above....when you have the same problem with 2 different replaceable components...usually that component ain't the problem. Be it a tire/rim or a driveshaft.


And HYRYSC...if you have any more questions for me....IM me...be glad to try and help, but I am done with this thread. I don't mind trying to help, but it's not worth arguing over with someone who won't listen.


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XJwonders

thank you for constructing a good argument in a civil manner. I appreciate it