612to303 Posted July 21, 2011 Share Posted July 21, 2011 Hey Everybody So I Have an 89 4wd 4.0 5 speed with an insane case of death wobble. Ive been lurking around a couple of forums and saw some of the causes were bad trac bar bushings Lca bushings, tire alignment, shocks etc. Now what I'm wondering is if i buy a 4.5 inch lift kit with trac bar, shocks, lower control arms and all the bushings and add 31s will my 3.07 gears be able to handle it? Does anybody have an idea of what the MPGs will be? The jeep will be used almost only going to breckenridge on I70 so the speed will be around 55-75. Thanks to anyone who can help. :waving: Link to comment Share on other sites More sharing options...
Incommando Posted July 21, 2011 Share Posted July 21, 2011 Honestly, every case of XJ death wobble that I have seen personally was a result of the trac-bar. That includes a wobbled-out trac bar mount hole on the body side that just replacing the bar would not correct. So if that is your problem a new trac bar will not help. To clarify: I am NOT saying that ALL cases of XJ/MJ DW are from the trac bar, just that every case that I have PERSONALLY seen have been the trac bar. Link to comment Share on other sites More sharing options...
87Warrior Posted July 21, 2011 Share Posted July 21, 2011 I fear that the 31's will not be livable making the trek from the Front Range to Breck. Our '93 XJ with AW4 and 3.55's with 30" tires looses a lot of steam when heading up to the tunnel, struggling to hold 55-60mph without rev'ing to 4K RPM. When I lived in Vail that poor XJ got used hard making it up and over the highway passes and it really isn't far from stock. You will probably be very unsatisfied with your truck trying to turn the 31's with 3.07s. I personally believe 4.10s and 31's are the best match, but others prefer the gearing to be a bit higher such as 3.55 or 3.73. Add worn out TRE's to you possible DW cause list. Link to comment Share on other sites More sharing options...
612to303 Posted July 21, 2011 Author Share Posted July 21, 2011 Thanks for the replys! Do you guys know a ballpark estimate of the fuel economy with 31s and 4.10s or 3.73s on highway? Thanks! Link to comment Share on other sites More sharing options...
Pete M Posted July 21, 2011 Share Posted July 21, 2011 your fuel economy won't change much with the various ratios. what will change is you will no longer curse your truck because it can't get out of it's own way with those awful 3.07s. :D opinions vary though on 31s on 3.07s. some guys say it's not that bad. i HATED my truck with 3.07s and 30" tires. simply upgrading to 3.55s after the Dana 35 blew up put the smile back on my face. :yes: Link to comment Share on other sites More sharing options...
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