Vibrations between 30 and 40 mph's - JeepForum.com
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post #1 of 29 Old 08-18-2019, 07:36 AM Thread Starter
mikewiz38
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Vibrations between 30 and 40 mph's

I've discovered a vibration and not exactly sure how to diagnose it. I would say that it happens between 30 and 40 mph's, with it mostly going away at about 45 through a faster vibration felt in the steering wheel. When I press down on the clutch, the vibration goes away. I'm guessing the wheels are not the issue because of the vibration going away on clutch down.

I thought maybe it's a drive shaft vibration, but now that I think about it, I'm not disconnecting the driveline when I push in on the clutch. So now my next guess is maybe a transmission mount, but I'm just guessing here.

I do need a new skid plate. The original one was rusted and I just por-15'ed it. When I reinstalled it, the acorn bolts were mostly gone due to rust, and I replaced them with hex bolts with a big washer. When tightening, the washers kind of broke through the rust ridden skid plate, but some bolts took. I also replaced the transmission mount, but had a heck of a time trying to get things lined up right....so I remember one of the bolts never torqued to spec, possibly due to me stripping it. I thought I was going to replace the skid plate soon and I'll just get a new transmission mount when I did that.

The other thing that happened when I took the drive shafts out is that the u-joint cap popped off and I just pushed it back on. I guess you can also guess that I took the u-joint straps off too but when I reinstalled them I used loc-tite.

Now I'm not exactly sure what I can do to diagnose it. There's a few ideas that I mentioned but I don't want to be just replacing parts willy nilly. Everybody here has been great and a wealth of knowledge so I appreciate any comments!

Thanks!


1994 Wrangler YJ - 4.0L - 5 Speed
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post #2 of 29 Old 08-18-2019, 01:44 PM
Brad Perryman
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Originally Posted by mikewiz38 View Post
I've discovered a vibration and not exactly sure how to diagnose it. I would say that it happens between 30 and 40 mph's, with it mostly going away at about 45 through a faster vibration felt in the steering wheel. When I press down on the clutch, the vibration goes away. I'm guessing the wheels are not the issue because of the vibration going away on clutch down.



I thought maybe it's a drive shaft vibration, but now that I think about it, I'm not disconnecting the driveline when I push in on the clutch. So now my next guess is maybe a transmission mount, but I'm just guessing here.



I do need a new skid plate. The original one was rusted and I just por-15'ed it. When I reinstalled it, the acorn bolts were mostly gone due to rust, and I replaced them with hex bolts with a big washer. When tightening, the washers kind of broke through the rust ridden skid plate, but some bolts took. I also replaced the transmission mount, but had a heck of a time trying to get things lined up right....so I remember one of the bolts never torqued to spec, possibly due to me stripping it. I thought I was going to replace the skid plate soon and I'll just get a new transmission mount when I did that.



The other thing that happened when I took the drive shafts out is that the u-joint cap popped off and I just pushed it back on. I guess you can also guess that I took the u-joint straps off too but when I reinstalled them I used loc-tite.



Now I'm not exactly sure what I can do to diagnose it. There's a few ideas that I mentioned but I don't want to be just replacing parts willy nilly. Everybody here has been great and a wealth of knowledge so I appreciate any comments!



Thanks!


Do you have a lift ket on the Jeep?


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post #3 of 29 Old 08-18-2019, 03:48 PM Thread Starter
mikewiz38
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Originally Posted by Brad Perryman View Post
Do you have a lift ket on the Jeep?


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I actually do but it's nothing significant. I bought a Crown "LSK4" 1" to 1.5" lift it. After it's been installed, it's about a 1" lift from stock.

When I installed the lift kit, I way overtorqued the shackle nuts, which has caused the bushings to tear. I ordered new bushings and they should be here tomorrow.

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post #4 of 29 Old 08-18-2019, 04:58 PM
K0LCB
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I think you may have a bad u-joint

L. C. AKA LEONARD
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post #5 of 29 Old 08-18-2019, 05:13 PM Thread Starter
mikewiz38
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Originally Posted by K0LCB View Post
I think you may have a bad u-joint
That's kind of what I'm thinking, even though I have no education in diagnosing the problem. Just really a process of elimination, since I've replaced a bunch of stuff already.

I took a look and the rear driveshaft has two greasable u-joints. I tried to grease them tonight and I couldn't get any grease into them. The little ball on the zerk fitting was able to be pressed in and even after that, the grease would just squirt out of the zerk. Not saying it's the sure fire way of telling, but I just wonder if maybe they've seen better days.

Is there a way to figure out which u-joint is causing this? And how bad is bad? Right now it's a small vibration that's felt in the steering wheel and barely noticeable in the jeep. I'm planning an 800 or so mile trip in about a month and don't know if I should tackle it before or after the trip.

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post #6 of 29 Old 08-18-2019, 09:03 PM
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Changing u joints is fairly simple. And if you haven't changed any, ya might as well do them all now before your trip.

You feeling it in the steering wheel and nowhere else is quite odd.

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
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post #7 of 29 Old 08-19-2019, 05:19 AM
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I had a U joint go bad last week; same symptoms including steering wheel shake. When I pulled the caps off of the U joint, there was just dust in there for grease, and I could tell they had gotten hot. $15 later, smooth sailing!
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post #8 of 29 Old 08-19-2019, 06:32 AM Thread Starter
mikewiz38
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Originally Posted by bruinjeeper View Post
Changing u joints is fairly simple. And if you haven't changed any, ya might as well do them all now before your trip.

You feeling it in the steering wheel and nowhere else is quite odd.
That's kind of what I'm thinking, but I think I might just do the drive-shaft ones because I can't feel the vibration when I have it in neutral. The u-joints behind the front wheels look more painful to do anyways.

What's an easier tool to use, one of those ball joint C-clamp like presses or a 6-ton harbor freight A-frame press to get the u-joints out? I'm leaning towards the ball joint press because autozone can loan it out to you. But I've had bad luck when you try to use a tool that's not specifically made for the job.

One more question. I had both drive-trains out when I did my tub/frame swap. Could the problem be that the I didn't properly align things properly when reinstalling? Chilton says to do this to "avoid vibration in the drivetrain".

Thanks!

1994 Wrangler YJ - 4.0L - 5 Speed

Last edited by mikewiz38; 08-19-2019 at 06:42 AM. Reason: added alignment piece.
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post #9 of 29 Old 08-19-2019, 07:38 AM
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Quote:
Originally Posted by mikewiz38 View Post
That's kind of what I'm thinking, but I think I might just do the drive-shaft ones because I can't feel the vibration when I have it in neutral. The u-joints behind the front wheels look more painful to do anyways.

What's an easier tool to use, one of those ball joint C-clamp like presses or a 6-ton harbor freight A-frame press to get the u-joints out? I'm leaning towards the ball joint press because autozone can loan it out to you. But I've had bad luck when you try to use a tool that's not specifically made for the job.

One more question. I had both drive-trains out when I did my tub/frame swap. Could the problem be that the I didn't properly align things properly when reinstalling? Chilton says to do this to "avoid vibration in the drivetrain".

Thanks!
As long as you did not take the drive shaft apart you should be good.
Yes I would change the u joints.
I like to use the C clamp presses to change them. It is easier than beating them out.
The A frame press will work too but if you do not have things lined up right you are taking a chance of bending the yokes.
You may want to check the angles of the drive shaft too, but with as little of lift you have on there it should be good.
I did how ever, way back when, have to have a transfer case drop with just a add a leaf.

93 YJ SOA 2" springs front, XJ springs rear w/main leaf added, High pinon 9 inch rear detroit locker front Dana 44 ARB 4.56 Gears, 36 inch Irok tires too much to list.
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post #10 of 29 Old 08-19-2019, 09:06 AM Thread Starter
mikewiz38
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Originally Posted by TSEJEEPERS View Post
As long as you did not take the drive shaft apart you should be good.
When you say take the drive shaft apart, do you mean off the car, or apart meaning like the inner workings of the driveshaft?

Thank You!

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post #11 of 29 Old 08-19-2019, 09:24 AM
Luuca
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vibration at speed that is repeatable on demand is usually a bent rim, out of balance tire, or out of spec alignment.

that said, U joints may be the culprit.
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post #12 of 29 Old 08-19-2019, 12:08 PM
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The first part of your post sounds like a textbook example of a drive shaft shudder caused by bad geometry. When a single joint is running at too much angle you will get a throttle or load sensitive vibration/shudder. This explains why pushing on the clutch would eliminate the vibration, pushing on the clutch does not stop or slow the drive shaft but it does unload the shaft. The part that has me unsure is that you have a very minor lift. I wouldn't expect a noticeable problem from a 1" lift. Another thing that could be causing the problem is non-parallel joint operation. For the stock shaft to work well, you need to have very little angle (which should be the case with you short lift), and you need the joints to be operating at the same angle. If someone has put a shim between your springs and your axle you may need to remove the shim. Here is what I suggest, measure the slope/angle of the drive shaft, of the transfer case, and of the differential. Report your findings.

To measure the angles you will need some sort of angle finder. You can download a digital level app on your phone. I have one called Clinometer. Then, to measure the drive shaft, just put your phone/tool right against the tube of the shaft. Find a flat spot on the t-case to measure off of. Finally, you can measure the differential by bridging your tool across two vertically spaced bolts on the differential cover.
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post #13 of 29 Old 08-19-2019, 12:46 PM Thread Starter
mikewiz38
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Originally Posted by ShawnAtTomWoods View Post
The first part of your post sounds like a textbook example of a drive shaft shudder caused by bad geometry. When a single joint is running at too much angle you will get a throttle or load sensitive vibration/shudder. This explains why pushing on the clutch would eliminate the vibration, pushing on the clutch does not stop or slow the drive shaft but it does unload the shaft. The part that has me unsure is that you have a very minor lift. I wouldn't expect a noticeable problem from a 1" lift. Another thing that could be causing the problem is non-parallel joint operation. For the stock shaft to work well, you need to have very little angle (which should be the case with you short lift), and you need the joints to be operating at the same angle. If someone has put a shim between your springs and your axle you may need to remove the shim. Here is what I suggest, measure the slope/angle of the drive shaft, of the transfer case, and of the differential. Report your findings.

To measure the angles you will need some sort of angle finder. You can download a digital level app on your phone. I have one called Clinometer. Then, to measure the drive shaft, just put your phone/tool right against the tube of the shaft. Find a flat spot on the t-case to measure off of. Finally, you can measure the differential by bridging your tool across two vertically spaced bolts on the differential cover.
Thank You! I actually do have a mechanical inclinometer. I'd be glad to report my findings with the information. I'm going to try to get to it tonight in a few hours.

Thanks!

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post #14 of 29 Old 08-19-2019, 05:28 PM Thread Starter
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Quote:
Originally Posted by ShawnAtTomWoods View Post
The first part of your post sounds like a textbook example of a drive shaft shudder caused by bad geometry. When a single joint is running at too much angle you will get a throttle or load sensitive vibration/shudder. This explains why pushing on the clutch would eliminate the vibration, pushing on the clutch does not stop or slow the drive shaft but it does unload the shaft. The part that has me unsure is that you have a very minor lift. I wouldn't expect a noticeable problem from a 1" lift. Another thing that could be causing the problem is non-parallel joint operation. For the stock shaft to work well, you need to have very little angle (which should be the case with you short lift), and you need the joints to be operating at the same angle. If someone has put a shim between your springs and your axle you may need to remove the shim. Here is what I suggest, measure the slope/angle of the drive shaft, of the transfer case, and of the differential. Report your findings.

To measure the angles you will need some sort of angle finder. You can download a digital level app on your phone. I have one called Clinometer. Then, to measure the drive shaft, just put your phone/tool right against the tube of the shaft. Find a flat spot on the t-case to measure off of. Finally, you can measure the differential by bridging your tool across two vertically spaced bolts on the differential cover.
OK, while I'm a novice at doing this, I think I have my numbers. For the transmisison one, I measured on the passenger side against a bump (maybe a bolt mount?) that was on it. All numbers are in degrees.

Front Driveshaft: 2.3
Transmission: 6
Rear Driveshaft: 20
Rear Differential: 7.5

I'm pretty sure I did everything correctly, but please let me know if a number sounds way off. Thank You!!

EDIT: I went back out and jiggled the drive shafts around a bit. The rear one seems solid but the front drive shaft has a little jiggle to it. Part of me thinks maybe it should be this way but another part things that the jiggle is going to make it slightly vibrate at speed.

I don't know if it helps, but I made a 10 second youtube video of what I'm talking about...


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Last edited by mikewiz38; 08-19-2019 at 05:56 PM. Reason: Added youtube video.
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post #15 of 29 Old 08-20-2019, 06:04 AM
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Quote:
Originally Posted by mikewiz38 View Post
OK, while I'm a novice at doing this, I think I have my numbers. For the transmisison one, I measured on the passenger side against a bump (maybe a bolt mount?) that was on it. All numbers are in degrees.

Front Driveshaft: 2.3
Transmission: 6
Rear Driveshaft: 20
Rear Differential: 7.5

I'm pretty sure I did everything correctly, but please let me know if a number sounds way off. Thank You!!

EDIT: I went back out and jiggled the drive shafts around a bit. The rear one seems solid but the front drive shaft has a little jiggle to it. Part of me thinks maybe it should be this way but another part things that the jiggle is going to make it slightly vibrate at speed.

I don't know if it helps, but I made a 10 second youtube video of what I'm talking about...

https://youtu.be/bqulNKPgiHo
That looks more like a loose slip joint to me. That u-joint was moving on an axis it is supposed to move on. However the entire driveshaft shouldnt move like that

1995 YJ. 2 inch BDS Spring lift. 1 inch shackle lift. 1.25 inch JKS Body Lift 33x12.5x15's. Engo 10,000 pound winch.

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. It started with a $200 axle, and a few thousand dollars later I was done :)
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Originally Posted by Luuca View Post
diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...
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this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.
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