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Unread 08-03-2015, 08:40 PM   #1
carnell
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Not so good vibration

Finished a AX-15 conversion to my 86 CJ7. I've now noticed that at 15 mph and between 35 and 45 mph I get a decent vibration. Same thing if I'm decelerating. The vibration goes away once the clutch is in (at the above stated speeds). Could my new driveshafts (original but modified for shorter length) be out of balance? If thats the case, going at the above speeds even with the clutch in, there still would be a vibration right?

Chappy

Before the mod, my T176 was super smooth. I hate to say it but I kinda miss it

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Unread 08-03-2015, 10:00 PM   #2
Mikey37
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Well I am not a pro but I will chime in and hope it helps. I think driveshaft moves as your wheels do so I would think that it would be felt at all times, maybe get worse with speed? (not the drug) lol .... sounds like you know more than me about this kind of thing so I imagine you checked usual suspects (tires bearings rotors etc) and if so then all I can say is good luck and someone will chime in with more knowledge than I. I am a simple back yarder going on limited experience and a bit of common sense lol of course if your shaft was modded then it's likely out of balance or at least get it checked...
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Last edited by Mikey37; 08-03-2015 at 10:11 PM..
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Unread 08-03-2015, 10:33 PM   #3
BagusJeep
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Out of balance driveshafts or worn out U joints or driveshafts assembled with the slip joint misaligned, such that the centreline of the joints at each end are not in the same plane.

Is it lifted at all?

When they wer changed in length, did you have them rebalanced?
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Unread 08-03-2015, 11:53 PM   #4
carnell
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Quote:
Originally Posted by BagusJeep View Post
Out of balance driveshafts or worn out U joints or driveshafts assembled with the slip joint misaligned, such that the centreline of the joints at each end are not in the same plane.

Is it lifted at all?

When they wer changed in length, did you have them rebalanced?
I have a 3 in lift. The rear & front both were cut to size, rebalanced with new U joints. I haven't used it in 4wd yet so all the vibes I'm feeling are while driving 2wd.

I don't remember how to check the plane??

I can call the driveline shop tomorrow and ask them to rebalance it. Not sure how they could mess that up.

Chappy
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Unread 08-04-2015, 06:02 PM   #5
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Unread 08-04-2015, 07:21 PM   #6
Mikey37
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Quote:
Originally Posted by carnell View Post
I have a 3 in lift. The rear & front both were cut to
size, rebalanced with new U joints. I haven't used it in 4wd yet so all the vibes I'm feeling are while driving 2wd.

I don't remember how to check the plane??

I can call the driveline shop tomorrow and ask them to rebalance it. Not sure how they could mess that up.

Chappy

Last edited by Mikey37; 08-04-2015 at 07:37 PM..
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Unread 08-04-2015, 07:22 PM   #7
Matt1981CJ7
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Since the vib goes away with the clutch in, it's most likely related to torque on the engine/driveline.

Have you checked your engine and trans mounts?

Matt
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Unread 08-04-2015, 10:51 PM   #8
carnell
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Quote:
Originally Posted by Matt1981CJ7 View Post
Since the vib goes away with the clutch in, it's most likely related to torque on the engine/driveline.

Have you checked your engine and trans mounts?

Matt
Trans mount is new and was done when I installed the transmission. The engine mounts are about 7 years old. I did remove the PS mount last month when I dropped my oilpan.

One thing worth noting, even though I hand the engine supported with a jack, when I removed the PS mount, the engine dropped a bit even though the DS mount was still connected. Could that have started my issue?

I only drove it once with the new transmission before I replaced the oilpan gasket.
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Unread 08-05-2015, 02:12 AM   #9
Matt1981CJ7
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I'd put the Jeep on jack stands, run it in gear, and look for the source of the vibration.

Matt
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Unread 08-05-2015, 07:39 AM   #10
carnell
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Quote:
Originally Posted by Matt1981CJ7 View Post
I'd put the Jeep on jack stands, run it in gear, and look for the source of the vibration.

Matt
Good idea!!

I'll give that a shot over the weekend and see what I come up with. Thanks for the idea.
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Unread 08-05-2015, 08:20 AM   #11
LumpyGrits
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Cj

Did you remove the slip spline during this install?
The DS might be out of 'phase'.
CK for play in the 'joints' and s'spline.
Grease them too.
What was the difference in length between the 2 tannys?
LG
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Unread 08-05-2015, 08:35 AM   #12
carnell
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Quote:
Originally Posted by LumpyGrits View Post
Did you remove the slip spline during this install?
The DS might be out of 'phase'.
CK for play in the 'joints' and s'spline.
Grease them too.
What was the difference in length between the 2 tannys?
LG
I know the DS was ballanced once it was re-sized. Joints are tight and new. The new tranny is a bit longer so my rear shaft was cut shorter. Don't remeber the numbers...
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Unread 08-05-2015, 11:39 AM   #13
LumpyGrits
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Cj

To much angle on the DS then.
May have to go to a double carden type u-joint deal.
The top DS in the picture is what I speak of.
http://www.pirate4x4.com/tech/billav...t/DCP_6524.JPG.

You could also try rotating up the rear pinion 2-3* with shims under the axle spring pad.
LG
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Unread 08-05-2015, 12:13 PM   #14
carnell
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That's about the size of my new DS. I'll contact the shop and get a price.
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Unread 08-15-2015, 04:27 PM   #15
carnell
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The vibration is gone! The transmission got dropped an inch so the twin sticks could fit and that alone, took away the vibes.
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