Front to back rocking after gear change -
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Unread 09-02-2013, 06:27 PM   #1
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2005 TJ Wrangler 
Join Date: Mar 2013
Location: CenCal, California
Posts: 44
Front to back rocking after gear change

-1999 Wrangler Sport/manual trans/stock 231 TC w/1 inch drop
-2.5 inch springs w/1.75 front spacer on 33's
-front D30(open) and rear 8.8 (limited slip) geared to 4.88

Ok, within the last couple months I completed a 8.8 swap with Artec and geared the 8.8 and stock D30 to 4.88 from 3.07 (love it). While saving up for the SYE, driveshaft and control arms I dropped the transfer case an inch to get rid of the vibes to break in the gears. After about 450 miles I changed the diff fluid and found nothing out of the ordinary inside other than the expected microscopic shavings.

Yesterday a buddy and I hit an nice intermediate rock trail to check out the new axle and gears. I quickly noticed while crawling in 4low w/tranny in 1st on declines and some level areas the Jeep would rock front to back over the rocks like a boat and I could hear a clack, clack noise as if the ring and pinion teeth were smacking together The engine would also surge when rocking like it was going to die then slightly rev up to maybe 1100 RPM as if I just touched the throttle. To stop the rocking I just touched the brake a little or would stop and start again but I could only think that I was going to bust a ring tooth. While on inclines everything was nice and smooth.

My first thought was I had too much backlash but during my regear I made sure everything was to spec. When I got home I checked my driveshaft slop by rotating both driveshafts with my hand w/trans in neutral and TC in 2H. I could rock the driveshafts maybe 1/6 or 1/5 or a turn before hearing the ring and pinion engaging which I don't think is too much. FYI, the driveshaft ujoints are solid and while driving on the road everything seems fine.

Tomorrow i'll check the backlash and see if anything has changed but now I'm thinking my problem may be my TC or possibly this is just something that goes along with having 4.88's.

I never had any rocking problems with he 3.07's so what do you guys think? Anything else I should check like the TC and if so what do I need to do?

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Unread 09-04-2013, 01:12 PM   #2
Registered User
2005 TJ Wrangler 
Join Date: Mar 2013
Location: CenCal, California
Posts: 44
Rear axle backlash is good at .008, starting to think the problem may be TC slop or a engine fuel issue since the surging occurred mostly while on a decline. And when I climbed under the rear I found the two upper sway bar bolts on the axle were gone and it was super loose.
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