Strange noise after gear install

[cdhowell]

I posted on another site with little responce. Maybe I can get some help here. I have a 97 XJ, 8" Skyjacker lift and 33's. Also a Teraflex SYE, D30 front with a trutrac and 8.25 rear open. As builds come in stages I just regeared to 4:56 from 3:07's. Since then I have a noise that starts about 70mph. It is not steady, but it comes in and out kind of rythemic if you will. I did the gears and pinion depth was set to what was engraved on the pinion gear. Backlash was at .007 Everything works great but this noise has me a little worried. A friend with a 05 TJ seems to have the same thing happening with his D35 and 4:56. Any help to find and eliminate this would be appreciated.

[SavageSun4x4]

You say you have a: 8 inch lift, 33 inch tires and a 3:07 ratio rear axle, this is correct????:confused:

[RufftyTuffty]

Pop the cover after break-in at 500m.

The oil should be flakey but should have any filings or chucks.

Without hearing the noise it pretty hard to say...my guess is it's normal for 4.56's, 33's, 8" lift @ 70 mph ;)

~Mike

[dstryr99]

I would check the drive shaft and make sure its balacned properly. With the new 4.56 gears, the shaft is spinning a lot faster and you are probably getting some harmonic vibrations at high speeds.

I had the same issue on my jeep when i went to 4.88s and it turned out to be an improperly installed tone ring on the rear of my output shaft.


HTH,

Ryan

[4 Wheelers Supply]

Did you use aftermarket gears?

[cdhowell]

Yes I did, they were Superior. New bearrings and seals. And it does seem harmonic. And yes they were 3:07s from the factory with the mods I mentioned.

[OlneyJeeps]

do you have a CV rear driveshaft? with lower gears, you are turning higher rpm... constant higher rpm+high angle=ingrediants for harmonic imbalance

[cdhowell]

I have a cv shaft, Mesa driveshaft built it. Do you think it could need rebalanced? Pinion angle seems to be pretty close. Leafs in the rear, but maybe more shim? Or dont worry about it and turn up the radio?

[dstryr99]

You can always remove the rear shaft and drive it in 4 hi and see if the vibes go away. If they don't, I would do the same thing with the front shaft.

That should help to pinpoint the problem.

Ryan

[cdhowell]

I'll try it this weekend