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Highway speeds vibes/moan

SqueegieSteve

SqueegieSteve

NAXJA Forum User
Location
Boston, MA
98' with rubicon superflex lift 3.5" in back and about 4" in front with spacers (31" AT's)
Hack'n'tap with 4deg shims in rear...

i have been trying to track down these vibes and they are driving me nuts! out of nowhere they showed up. They start at around 35mph and the vibes/groans get worse/louder as i drive faster. It's more of a groan then a shaking vibration. i pulled the front DS and the vibes are still there. Any ideas of where i should go next? Th U-joints looked good in the front and the rears only have about 3000 miles on them.
:banghead:
 
Put it in 4Hi, pull the rear drive shaft, and go for a drive.

U-joints "looking good" and actually being good are not always the same thing.

At least try to pinpoint the source of the noise to the front or the rear of the Jeep.
 
Last edited:
Tim_MN said:
Put it in 4Hi, pull the rear drive shaft, and go for a drive.

U-joints "looking good" and actually being good are not always the same thing.

At least try to pinpoint the source of the noise to the front or the rear of the Jeep.
Click to expand...

You've got a good point. Just this winter i put in the hackntap and rear DS though so i haven't even considered the possibility of the rear U-Joints being bad... i could try this later though.

If i had a bad unit bearing wouldn't it be obvious which one it was and where on the car the vibes were coming from?
 
I know you have a 4deg shim in the rear, but is the angle correct? Are your wheel and carrier bearings good? Check U-joints. Is sound more or less with turns, which direction is worse?
 
I would pull your front shaft. Go for a drive.

I fought with a vibe, thinking it was my hack n tap. Turned out to be the FRONT pinion angle. I still haven't fixed it. 3 driveshafts later.
 
SqueegieSteve said:
i pulled the front DS and the vibes are still there.
Click to expand...

What SYE kit did you use,the late model T-case can be problematic.I tried a H-n-T on my 2000 for about a month,I had to go to a HD kit, that was 11yrs ago and no problems since.
 
93gc40 said:
I know you have a 4deg shim in the rear, but is the angle correct? Are your wheel and carrier bearings good? Check U-joints. Is sound more or less with turns, which direction is worse?
Click to expand...

- i think my shims were good because they eliminated all vibes for a year
- the sound doesn't change with turns either
 
did this start out of the blue?
did the vibs start after you installed your lift?
did they start after your hack n tap?
you can try getting your drive shaft a hi speed balance if you got low range gears. sometimes with low range gears you will get a drive shaft vib because the ds is spinning faster. alot of ds shops dont do high speed balancing unless you request it.
 
SqueegieSteve said:
Why exactly did you have to go to the HD kit?
Click to expand...

Because I still had minor vibes and wanted it perfect.Remember this was a brand new Jeep,only had 30 miles on it when I lifted it !!
 
SoCal Off-Road said:
you can try getting your drive shaft a hi speed balance if you got low range gears. sometimes with low range gears you will get a drive shaft vib because the ds is spinning faster. alot of ds shops dont do high speed balancing unless you request it.
Click to expand...

This is very true,alot of shops dont have the machine for this.
 
SoCal Off-Road said:
did this start out of the blue?
did the vibs start after you installed your lift?
did they start after your hack n tap?
you can try getting your drive shaft a hi speed balance if you got low range gears. sometimes with low range gears you will get a drive shaft vib because the ds is spinning faster. alot of ds shops dont do high speed balancing unless you request it.
Click to expand...


It was out of the blue that these showed up. The other things that you mentioned i did about a year ago..
After closer inspection is seems that those 4deg shims might not be anough. But i don't see how this could start the vibes out of the blue. Wouldn't i have noticed them right after i installed the hackntap and the 4deg spacers?

Anybody know what the typical shim angle to get is for a 3.5inch lift?
 
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