Rear End Thud! - JeepForum.com
 
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post #1 of 8 Old 03-11-2010, 12:51 PM Thread Starter
ckritcoad
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1986 CJ7 
 
Join Date: Jul 2006
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Rear End Thud!

I just put a 9" rear end in the CJ. Everything went fine, but when I put it in drive or reverse the pinion jolts pretty violently and makes a pretty bad noise. Is this a back lash problem...would the pinion bolt not being torqued enough cause this?

Thanks for your help!

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post #2 of 8 Old 03-11-2010, 01:35 PM
78treehugger
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Looks like you have an auto. Is the axle rotating causing the pinion to load an unload? Are your perches good? Did you rebuild the axle before installing it? If not did you check the bearings?

1980 CJ 7--3" Black Diamond, 1" body, locked both ends, 4.56, 35x12.50x15 SS LTB, "family" cage

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post #3 of 8 Old 03-11-2010, 02:41 PM Thread Starter
ckritcoad
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I got the center section and supposedly it was just built and run for 400 miles with no problems. I changed the yoke to the correct size and installed new axles. The spring perches are good and solid. It does feel like it is loading and uloading when I put it in drive or reverse...yes it is an auto.
FYI it is a LSD. The bearings looked good and I didn't feel any slop or movement.

Thanks for your help!
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post #4 of 8 Old 03-11-2010, 03:58 PM
UPJ Wheeler
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Make sure your U bolts are tight for the springs. Mine tend to loosn up over time, and then the axle will rotate about 20 degrees or so and make loud banging noises when getting on or off the gas. Simple Fix

'79 CJ7, rebuilt 258, HEI, T5 World Class, D300 Low max 4:1, Flat Belly, Narrowed D44 w/ true trac & diff gaurd, Widetrack AMC20 w/ superior shafts, Detroit locker & crane diff cover, 4" skyjacker lift, 2" BL, TJ flares, 35" tires, York OBA, YJ tub conversion, 6 pt. cage, F250 front shock towers

4.0 Head and TBI on the way
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post #5 of 8 Old 03-11-2010, 04:07 PM Thread Starter
ckritcoad
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Quote:
Originally Posted by UPJ Wheeler View Post
Make sure your U bolts are tight for the springs. Mine tend to loosn up over time, and then the axle will rotate about 20 degrees or so and make loud banging noises when getting on or off the gas. Simple Fix
They are good and torqued down...I will try them again though.
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post #6 of 8 Old 03-12-2010, 08:24 AM
CSP
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It's either backlash or bad ujoints.
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post #7 of 8 Old 03-13-2010, 05:13 PM Thread Starter
ckritcoad
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Quote:
Originally Posted by UPJ Wheeler View Post
Make sure your U bolts are tight for the springs. Mine tend to loosn up over time, and then the axle will rotate about 20 degrees or so and make loud banging noises when getting on or off the gas. Simple Fix
Amazingly enough it was my U bolts. Apparently my compressor and gun are extremely week. I figured I had torqued them down too much, but when I had it at work in our shop and checked them with a digital torque wrench they were only torqued down between 35 and 45 ft/#'s. I torqued them to 100 and they problem completely went away. Thanks for the suggestion!
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post #8 of 8 Old 03-14-2010, 07:31 AM
UPJ Wheeler
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no problem....

'79 CJ7, rebuilt 258, HEI, T5 World Class, D300 Low max 4:1, Flat Belly, Narrowed D44 w/ true trac & diff gaurd, Widetrack AMC20 w/ superior shafts, Detroit locker & crane diff cover, 4" skyjacker lift, 2" BL, TJ flares, 35" tires, York OBA, YJ tub conversion, 6 pt. cage, F250 front shock towers

4.0 Head and TBI on the way
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