93 YJ bad vibs at idle, jerking at takeoff? - JeepForum.com
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Unread 10-23-2013, 06:02 AM   #1
redscustoms
Registered User
1993 YJ Wrangler 
 
Join Date: Jul 2012
Location: shrewsbury, NJ
Posts: 1
93 YJ bad vibs at idle, jerking at takeoff?

Alright guys. I'm stumped! I've got a 93 YJ 2.5l that I've had for a little over a year now that I've been doing non stop work on. Its been fun but now I'm getting a little agitated. I need some help.

So a couple of weeks ago I started noticing a vibration between 30-50mph. So I checked the ujoints and the ujoint at the slip yoke was shot. Replaced both of them to find that it made the vibs better but not completely. So next was the trans mount. That was shot, replaced that and that's when the jerking into first gear started. I didn't want to even think about the idea of it being the clutch so I went to the motor mounts next. Turns out the mounting plate on the pass side was ripped off the frame. So I replaced that and both motor mounts. Now it vibrates all the time and jumps letting the clutch out into first. But If I release the clutch slowly at 1500+ it won't jerk.

RECAP:
-new u joints
-new trans mount
-new motor mounts
-trans/tcase/rear diff fluids all good
-plugs good
-no vacuum leaks

I'm thinking the clutch may be warn. Plate glazed. Bearings bad. Something along those lines. But what I can't figure out, is why does it vibrate so bad all the time? Specifically at idle in neutral. Bad flywheel? But it doesn't get better or worse when clutch is engaged.I don't know. Any guidance would be greatly appreciated.

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Unread 10-23-2013, 05:45 PM   #2
superj
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1987 YJ Wrangler 
 
Join Date: Mar 2008
Location: corpus christi, texas
Posts: 6,445
All the time sounds weird. Do the 2.5l have vibration dampners on the flywheel? Or a counter balanced crank shaft? Maybe one of the weights are stuck on the crank shaft? Does the engine have a vibration dmpner on the end of the crank up front? Looks like a pulley with a rubber center piece?
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Unread 10-24-2013, 12:06 AM   #3
NonRubicon
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1990 YJ Wrangler 
 
Join Date: Nov 2009
Location: The southern armpit of California
Posts: 2,087
It sounds like the motor mount bolts are too tight. Something as little as 1/4 a turn on the nut can result in vibes, even though there is little resistance when you turn the nut.

I suggest you try backing the nuts off maybe 1/4 turn increments, checking for vibes as you go along - if no vibes at idle, then test drive to see if you get vibes when you take off from a stop.

Also make sure the trans mount bushing and the motor mount bushings are the same material. Mixing poly and rubber can cause vibes.
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